The R2R3-MYB gene family in Arabidopsis thaliana

Dynamics of cytosolic and organellar gene transcripts in wild and cultivated genotypes of pigeon pea due to simulated herbivory

Pigeon pea (Cajanus cajan), widely grown in India, suffers significant yield losses due to pod borers (Helicoverpa armigera and Maruca vitrata). Therefore, studying the host resistance mechanism is pivotal for crop improvement. In this study, we conducted transcriptome analysis on two wild-type (WT) Cajanus scarabaeoides accessions (ICP-15761 and ICP-15738) having high levels of resistance to pod borers and two cultivated C. cajan genotypes, ICPL-332 (moderately resistant) and ICPL-87 (susceptible), following simulated herbivory with H. armigera oral secretions (OS). Differential gene expression analysis identified 3573 and 4677 differentially expressed genes (DEGs) in ICP-15761 and ICP-15738, whereas 4149 and 3639 DEGs were documented in ICPL-332 and ICPL-87, respectively. Genes related to chloroplast biogenesis, photosynthesis, and chlorophyll metabolism exhibited significant differential expression, indicating chloroplast reprogramming under simulated herbivory. Significant upregulation of key defense genes, including chitinases and cysteine proteases, in C. scarabaeoides accessions highlighted robust defense pathway activation. A genotype-specific shift in transcription factors, phytohormones, and calcium signaling-related gene expression was noted. Higher levels of expression of aspartic proteinases and pathogenesis-related proteins in cultivated genotypes suggesting adaptive evolutionary traits. This is a novel insight on molecular mechanism of defense in a wild type, C. scarabaeoides and cultivated genotypes of pigeon pea under simulated herbivory. The information on cytosolic and organellar gene changes in pigeon pea due to H. armigera OS mediated-simulated herbivory may help develop pigeon pea varieties that are resistant to pod borer infestations.

Overexpression of NtMYB306c reduces the glandular trichomes density in tobacco

Trichomes, as multicellular structures with diverse functions, play a crucial role in protecting plants against various stresses. Nicotiana tabacum (tobacco) leaves are characterized by numerous glandular trichomes, which are responsible for the production of substantial quantities of secondary metabolites and are critical determinants of tobacco quality. Although their importance is well established, the molecular regulatory mechanisms governing the development of tobacco glandular trichomes remain poorly characterized. Through comparative transcriptome analysis of trichome and trichome-free leaves, we identified NtMYB306c, an R2R3-MYB transcription factor that is phylogenetically distinct from its paralog NtMYB306a (designated as NtMYB306e in this study) and shows highly expressed in trichomes. Functional characterization revealed that overexpression of NtMYB306c significantly suppresses glandular trichome density and markedly alters the expression of three key regulatory genes, NtJAZ3, NtCycB2 and NtHD9 and the key gene LOX1 in JA biosynthesis. Protein-protein interaction screening identified NtMYB308, another member of the R2R3-MYB family. Bioinformatic analysis predicted that its Arabidopsis thaliana homolog interacts with GL3, EGL3, and TTG1, core components of the MBW complex that regulates Arabidopsis glandular trichome development. Yeast two-hybrid (Y2H) and co-immunoprecipitation (Co-IP) assays confirmed the physical interaction between NtMYB306c and NtMYB308, while bioinformatic analysis identified MYB binding sites in the promoter region of NtJAZ3. Collectively, our study demonstrates that NtMYB306c regulates the density of tobacco glandular trichomes via its interaction with NtMYB308.

The ZjMYB44-ZjPOD51 module enhances jujube defense response against phytoplasma by upregulating lignin biosynthesis

Lignin is a major component of the plant cell wall and has a conserved basic defense function in higher plants, helping the plants cope with pathogen infection. However, the regulatory mechanism of lignin biosynthesis in plants under phytoplasma stress remains unclear. In this study, we reported that peroxidase 51 (ZjPOD51), which is involved in lignin monomer polymerization, was induced by phytoplasma infection and that overexpression of ZjPOD51 in phytoplasma-infected jujube seedlings and Arabidopsis plants significantly increased their defense response against phytoplasma. Yeast one-hybrid (Y1H) and luciferase (LUC) assays showed that ZjPOD51 transcription was directly upregulated by ZjMYB44. Genetic validation demonstrated that ZjMYB44 expression was also induced by phytoplasma infection and contributed to lignin accumulation, which consequently enhanced phytoplasma defense in a ZjPOD51-dependent manner. These results demonstrated that the ZjMYB44-ZjPOD51 module enhanced the jujube defense response against phytoplasma by upregulating lignin biosynthesis. Overall, our study first elucidates how plants regulate lignin to enhance their defense response against phytoplasma and provides clues for jujube resistance breeding.

Molecular mechanism of SmMYB53 activates the expression of SmCYP71D375, thereby modulating tanshinone accumulation in Salvia miltiorrhiza

Tanshinones are bioactive diterpenoid chemicals of the herb Salvia miltiorrhiza with a characteristic furan D-ring. As a newly identified downstream enzyme, SmCYP71D375, catalyzes hydroxylation by 14,16-ether (hetero)cyclization to form the furan D-ring from the precursor of the phenolic abietane-type diterpenoids that exist widely in Lamiaceae plants. However, its transcriptional regulatory network, with SmCYP71D375 as the direct target gene, remains unclear. In the present study, the promoter of SmCYP71D375 was employed as the bait to mine the upstream regulatory protein using the cDNA yeast library of S. miltiorrhiza. An R2R3-MYB transcription factor gene, SmMYB53, was identified. Overexpressing SmMYB53 in transgenic hairy roots upregulated SmCYP71D375 expression, thereby accelerating tanshinone accumulation, whereas tanshinone accumulation was inhibited in SmMYB53-RNAi transgenic hairy root lines. To dissect the regulatory network of SmMYB53, SmbZIP51 was captured using SmMYB53 as the bait to prey for its potential interacting proteins in the cDNA yeast library. Yeast two-hybrid, glutathione S-transferase pull-down, and bimolecular fluorescence complementation assays were independently used to verify the interaction between the SmMYB53 and SmbZIP51 proteins . We further verified that the upregulation of SmCYP71D375 activated by SmMYB53 would be inhibited by the interaction of SmMYB53 and SmbZIP51. The present findings uncover the molecular regulatory network underlying SmCYP71D375 as the direct target regulating tanshinone biosynthesis and offer a basis for the genetic improvement of medicinal substance biosynthesis in S. miltiorrhiza.

Optimizing plant phosphate uptake: Advances in the core regulatory mechanisms of phosphate starvation response proteins and their macromolecular partners: A review

Phosphorus (P), essential for plant survival, is primarily absorbed as inorganic phosphate (Pi), yet soil Pi scarcity severely limits plant growth and agricultural productivity. This review synthesizes current research on plant adaptations to Pi scarcity, with a focus on the root system as the primary site of Pi absorption and the role of MYB transcription factors, particularly PHOSPHATE STARVATION RESPONSE 1 (PHR1), a core regulatory biological macromolecule. PHR1 orchestrates a wide array of genetic responses that modify root architecture to enhance Pi acquisition under nutrient-poor conditions. This review delves into the biological activities, molecular associations, chemical and biological modifications, and functional properties of PHR1 and related MYB transcription factors, examining how these regulatory macromolecular proteins interact with other molecular components to form complexes that coordinate adaptive root development. By integrating findings from diverse plant species, the review highlights the potential of leveraging molecular breeding techniques to develop cultivars with enhanced phosphate uptake efficiency by targeting these regulatory macromolecular proteins. Such advancements promise to mitigate the impacts of Pi deficiency, supporting sustainable agricultural and forestry practices. The insights provided aim to inform and guide future research in plant nutrient management, focusing on the intricate interplay of biological and molecular factors that regulate phosphate uptake.

The MYB-related transcription factor family in rubber dandelion (Taraxacum kok-saghyz): An insight into a latex-predominant member, TkMYBR090

MYB-related (MYBR) proteins play diverse roles in plant growth and development. However, the MYBR genes in Taraxacum kok-saghyz, a promising alternative source of natural rubber, a valuable biopolymer, remain scarcely investigated. Here, a total of 122 MYBR genes, namely TkMYBRs, were identified and classified into the groups of GARP-like, CCA1-like/R-R, and a heterogenous one in T. kok-saghyz. Collinearity analysis revealed a high similarity in MYBRs across two Taraxacum species with contrasting rubber yield. TkMYBR090 showed predominant expression in latex, the cytoplasm of rubber-producing laticifers. Transient overexpression of TkMYBR090 in tobacco and T. kok-saghyz demonstrated its localizations in nucleus and cytoplasm. Yeast two-hybrid assay revealed that the C-terminus of TkMYBR090 possessed transcriptional activation activity. DAP-seq analysis identified 18,232 TkMYBR090-targeted candidate genes, and four significantly enriched TkMYBR090 DNA-binding promoter motifs that were validated by yeast one-hybrid assay. The binding of TkMYBR090 on the promoter of an ascorbate oxidase gene was verified by yeast one-hybrid and dual luciferase activity assays, suggesting a role in ROS metabolism. Such assumption was supported by heterologous expression assays of TkMYBR090 in tobacco and yeast. This study is beneficial to further functional dissection of MYBRs in T. kok-saghyz, especially the roles in development and function of rubber-producing laticifers.

PcMYB44 regulated host resistance to Botryosphaeria dothidea through activation of lignin biosynthesis and disease-resistance gene expression in pear

Pear ring rot disease, the pathogen of Botryosphaeria dothidea causes significant threat to the healthy development of the pear industry, therefore the exploration of disease-resistant gene resources is crucial for disease prevention and control. Members of the R2R3-MYB subfamily play important roles in regulating pathogen resistance in plants, however the gene function in regulating host resistance in pear remains unclear. In this study, the role of PcMYB44 were investigated in regulating host resistance disease in pear calli using both forward and reverse genetic approaches. Overexpression of PcMYB44 positively regulates the disease resistance, whereas knockout of PcMYB44 results in a phenotype with decreased resistance. Our results further demonstrated that PcMYB44 could directly affect lignin content and resistance to fungal diseases by regulating the PcmiR397-PcLACs module and lignin biosynthesis gene expression levels. Additionally, overexpressing PcMYB44 also elevated expression levels of key genes of JA/SA/ET pathway. The obtained results revealed that PcMYB44 regulated host resistance to ring rot disease through synergistic regulation the lignification and activating disease-resistance gene expression of JA/SA/ET defense pathways as a underlying secondary mechanism, which provide valuable genetic resources for molecular breeding for disease resistance.

Interaction of R2R3-MYB transcription factor EgMYB111 with ABA receptors enhances cold tolerance in oil palm

The oil palm is a prominent tropical oil crop with holds considerable economic value. MYB transcription factors are key regulators in growth and plant stress adaptation mechanisms in plants. However, the roles and operational mechanisms of MYB genes in oil palm are not yet well understood. In this study, EgMYB111 was cloned from oil palm, and its behavior under cold stress was examined in genetically engineered tobacco and oil palm embryoids. Physiological and biochemical analysis demonstrated that genetically engineered lines exhibited substantially greater cold tolerance than control plants. EgMYB111 was noticed to localize within the nucleus, and cold stress significantly enhanced the expression of the GUS gene managed by the EgMYB111 expression regulator. Interestingly, EgMYB111 was involved in the reaction to stress via an abscisic acid (ABA)-mediated pathway. Yeast two-hybrid experiments confirmed the involvement of EgMYB111 and the ABA receptor proteins PYR1 and PYL9. Moreover, the transient transformation of oil palm protoplasts combined with qRT-PCR analysis revealed that the over-activity of EgMYB111 induced a significant induction of the genes EgSnRK2.1, EgSnRK2.3, and EgSnRK2.5. In addition, dual-luciferase analyses, yeast one-hybrid assays, and electrophoretic mobility shift assays (EMSA) established that EgMYB111 binds to the promoters of EgSnRK2.1, EgSnRK2.3, and EgSnRK2.5, thereby regulating their transcription and enhancing low-temperature resilience in oil palm. The work concludes that the EgMYB111 performs a key role in augmenting cold adaptability in oil palm by governing the transcription of key genes utilizing an ABA-regulated pathway.

The 1R-MYB transcription factor SlMYB1L modulates drought tolerance via an ABA-dependent pathway in tomato

The MYB transcription factor family is one of the biggest transcription factors in plants, playing key roles in regulating many biological processes, including growth and development, responses to biotic and abiotic stresses and hormone signaling. In this study, we identified and characterized an 1R-MYB transcription factor, SlMYB1L, which is involved in regulating drought tolerance in tomato. SlMYB1L-RNAi transgenic plants displayed more severe dehydration phenotype with elevated malondiadehyde (MDA) and hydrogen peroxide (H2O2), as well as reduced proline content and antioxidant enzyme activities compared to wild-type under drought stress. Additionally, SlMYB1L influenced drought-induced stomatal closure and modulated endogenous ABA levels, leading to a decrease in the expression of ABA-related genes in SlMYB1L-RNAi transgenic plants. A dual-luciferase reporter assay further confirmed that SlMYB1L represses the expression of ABA catabolism gene SlCYP707A3. In conclusion, our findings suggest that SlMYB1L is a stress-responsive transcription factor that positively regulates drought tolerance and may serve as a candidate gene for developing drought-resistant crops.

Integrative analysis of the R2R3-MYB gene family revealed that BsMYB36 and BsMYB51 significantly regulate the accumulation of flavonoids in Bletilla striata (Orchidaceae)

The R2R3-MYB transcription factors constitute a critical family involved in a variety of biological processes. They have been found to be essential participants in flavonoid biosynthesis in various plants. Bletilla striata (Thunb.) Reichb. f. is an orchid species rich in flavonoid compounds, with anti-inflammatory and antioxidant properties. In this study, we identified 94 R2R3-MYB genes, 89 of them were classified into 22 subgroups, and 92 were mapped to 16 chromosomes. The S5 and S7 subfamilies contained three and four members, respectively which might play roles in the biosynthesis of anthocyanin, proanthocyanidin, and flavonoid. Additionally, BsR2R3-MYBs exhibited tissue-specific expression. There were 36 genes, and 35 genes exhibited high expression in roots and pseudobulbs, respectively. The 25 R2R3-MYB genes from different subfamilies showed varying responses to drought, low temperature, and MeJA treatments. Furthermore, the S5 subfamily member BsMYB51 and the S7 subfamily member BsMYB36 were heterologous expressed in A.thaliana. Phenotypic observations of A.thaliana showed that BsMYB36 and BsMYB51 could compensate for the growth differences caused by the atmyb12 and atmyb123 mutations, respectively. Moreover, the overexpression of BsMYB36 increased flavonoid content, while decreasing the accumulation of anthocyanin and proanthocyanidin in A.thaliana. The overexpression of BsMYB51 promoted the accumulation of flavonoid, anthocyanin, and proanthocyanidin. Overexpression of BsMYB36 and BsMYB51 significantly upregulated relative genes in the phenylpropanoid and flavonoid biosynthesis pathways, such as PAL, CHS, F3'H, and DFR. This study provids the foundation for exploring the regulation of flavonoid content by BsMYBs in B.striata.

Identification and functional characterization of MYB genes regulating polyphenol biosynthesis in cabbage for resistance to Xanthomonas campestris pv. campestris

Cabbage (Brassica oleracea L. var. capitata) is a vital leafy vegetable, but its production is frequently impacted by Xanthomonas campestris pv. campestris (Xcc). The MYB family is one of the most abundant families involved in plant responses to biotic stresses. However, genome-wide identification of MYB and their roles in regulating phenolic synthesis during Xcc resistance have not been previously reported in cabbage. The present investigation reports a total of 322 BoMYB genes. Transcriptome data revealed that 37 BoMYBs were significantly upregulated upon Xcc infection. Concurrently, an increase in polyphenol content was observed, suggesting a pivotal role of polyphenols in Xcc resistance. Based on phylogenetic relationships and qRT-PCR analysis, BoMYB108 was identified as a candidate gene potentially involved in early resistance to Xcc by regulating polyphenol biosynthesis. Overexpression and silencing experiments were conducted to validate the function of BoMYB108. Overexpression of BoMYB108 significantly enhanced the accumulation of phenolic acids, while silencing resulted in the opposite effect. Furthermore, increased phenolic acid levels were associated with reduced reactive oxygen species (ROS) accumulation. These findings indicate that BoMYB108 promotes phenolic acid biosynthesis and mitigates ROS accumulation under Xcc stress, thereby alleviating Xcc-induced damage. In summary, this study provides a valuable data resource for the MYB gene family in cabbage and establishes a theoretical foundation for understanding the phenolic-based mechanisms of Xcc resistance in brassicaceous vegetables.

Transcription factors in Orinus: novel insights into transcription regulation for speciation adaptation on the Qinghai-Xizang (Tibet) Plateau

BACKGROUND

Transcription factors (TFs) are crucial regulators of plant growth, development, and resistance to environmental stresses. However, comprehensive understanding of the roles of TFs in speciation of Orinus, an extreme-habitat plant on the Qinghai-Xizang (Tibet) Plateau, is limited.

RESULTS

Here, we identified 52 TF families, including 2125 members in Orinus, by methodically analysing domain findings, gene structures, chromosome locations, conserved motifs, and phylogenetic relationships. Phylogenetic trees were produced for each Orinus TF family using protein sequences together with wheat (Triticum aestivum L.) TFs to indicate the subgroups. The differences between Orinus and wheat species in terms of TF family size implies that both Orinus- and wheat-specific subfamily contractions (and expansions) contributed to the high adaptability of Orinus. Based on deep mining of RNA-Seq data between two species of Orinus, O. thoroldii and O. kokonoricus, we obtained differentially expressed TFs (DETFs) in 20 families, most of which were expressed higher in O. thoroldii than in O. kokonoricus. In addition, Cis-element analysis shows that MYC and G-box elements are enriched in the promoter region of DETFs, suggesting that jasmonic acid (JA) and abscisic acid (ABA) act synergistically in Orinus to enhance the signalling of related abiotic stress responses, ultimately leading to an improvement in the stress tolerance and speciation adaptation of Orinus.

CONCLUSIONS

Our data serve as a genetic resource for Orinus, not only filling the gap in studies of TF families within this genus but also providing preliminary insights into the molecular mechanisms underlying speciation in Orinus.

Genome-Wide Screening of the MYB Genes in Coptis chinensis and Their Roles in Growth, Development, and Heavy Metal Resistance

Background:Coptis chinensis is a traditional medicinal plant rich in bioactive compounds like berberine, known for its antibacterial, anti-inflammatory, and antioxidant properties. This study aims to analyze the MYB transcription factor family in C. chinensis to better understand their roles in plant growth, development, metabolism, and stress responses. Methods: We employed bioinformatics to conduct a genome-wide identification of MYB genes in C. chinensis, followed by analyses of physicochemical properties, phylogenetic relationships, gene structures, chromosomal localization, conserved motifs, cis-acting elements, and expression patterns. Results were validated using qRT-PCR. Results: A total of 129 CcMYB genes were identified across nine chromosomes. Phylogenetic analysis categorized these genes into 19 subgroups, notably highlighting the S6 subgroup, which lacks counterparts in Arabidopsis. Comparative genomics revealed segmental duplication among gene pairs. Transcriptomic analysis indicated that CcMYB21, CcMYB40, CcMYB105, and CcMYB116 had high expression levels in stems. Importantly, CcMYB94 expression significantly increased under cadmium stress, suggesting its role in stress regulation. Conclusions: This study offers a comprehensive analysis of the MYB gene family in C. chinensis, underscoring the significance of MYB transcription factors in enhancing the plant's medicinal value and stress tolerance, particularly against cadmium exposure. These insights pave the way for further exploration of specific MYB genes to improve stress resilience in C. chinensis.

Bioinformatics analysis and development of functional markers for TaMYB4-1A in wheat

MYB transcription factors play crucial roles in various stages of plant growth and development. Bioinformatics analysis revealed that wheat TaMYB4-1A contains two conserved MYB domain. The coding region of TaMYB4-1A is 792 bp, encoding 263 amino acids. TaMYB4-1A is a hydrophilic protein, and its encoded protein is localized in the cell nucleus. Evolutionary tree analysis indicates that the TaMYB4 protein shares the closest relationship with Aegilops, barley, and rye. Tissue-specific expression analysis revealed that TaMYB4-1A is expressed in wheat roots, stems, leaves, and seeds 14 days post-flowering, with the highest expression in the seeds. Promoter cis-acting element analysis showed that the promoter region of TaMYB4-1A contains various cis-acting elements, including meristem regulatory elements, drought-induced elements, and hormone response elements. qRT-PCR analysis showed that the expression of TaMYB4-1A is suppressed under high salinity and PEG treatment, suggesting that TaMYB4-1A may play a critical regulatory role in response to salt and drought stress. There are two haplotypes of TaMYB4-1A, namely Hap-1A-I and Hap-1A-II. The average plant height of varieties with haplotype Hap-1A-I is significantly higher than that of varieties with haplotype Hap-1A-II. This research provides a basis for future in-depth investigation of the biological function of the TaMYB4-1A gene and offers promising candidate genes for molecular marker-assisted wheat breeding.

Two duplicated GhMML3 genes coordinately control development of lint and fuzz fibers in cotton

Cotton produces two types of fibers: fuzz and lint. Cotton yield is determined by the number of epidermal cells that develop into lint fibers. Despite numerous studies, the genetic and molecular mechanisms that control lint and fuzz fiber development remain unclear. Here, using the recessive naked-seed or fuzzless-linted mutant (n2NSM) in combination with gene editing and complementation, we found that the recessive fuzzless gene n2 encodes the MYBMIXTA-like (MML) transcription factor GhMML3_D12. Overexpression of GhMML3_D12 in n2NSM restored fuzz fiber development, whereas CRISPR-Cas9 knockout of GhMML3_D12 in wild-type cotton (J668) resulted in a fuzzless-linted phenotype. Interestingly, simultaneous edits to GhMML3_D12 and its duplicate GhMML3_A12 resulted in plants with a fiberless (fuzzless-lintless) phenotype. Detailed investigation of the seed fiber phenotypes of segregating progeny derived from a cross between J668 and a fiberless gene-edited mutant of GhMML3 (#mml3s) not only identified progeny that mimicked natural fuzzless and fiberless mutants but also revealed that the duplicated GhMML3_A12 and GhMML3_D12 regulate the development of fuzz and lint fibers in a dose-dependent manner. Comparative transcriptome analysis and single-cell RNA sequencing identified GhMML3 as the central hub of the gene network that regulates fiber initiation and early-stage elongation. The gene regulatory network revealed potential candidate genes and key regulators that may contribute to fiber initiation and development, and a model for the control of lint and fuzz fiber development by GhMML3 was proposed. We also found that the GhMML3_D12 protein can bind directly to the promoters of GhHD-1 and GhMYB25, two key genes involved in fiber initiation, thereby activating their expression. This study provides new insights into the fundamental mechanisms that underlie cotton fiber development.

Identification of the regulatory role of SsMYBS25-4 in salt stress from MYB-related transcription factors in sugarcane (Saccharum spontaneum)

Sugarcane is a highly valued crop known for its significant production of sugar and biomass. MYB transcription factors (TFs) are critical regulators in plant growth and stress tolerance, but MYB-related genes, an atypical subset of the MYB family, remain less explored. In this study, we identified 119 MYB-related genes in the genome of wild sugarcane (S. spontaneum). We thoroughly investigated their phylogenetic relationships, chromosomal locations, motif compositions, and three-dimensional (3D) protein structures by bioinformatic methods. Moreover, the expression patterns of these genes demonstrated significant diversity in plant growth and under salt stress. One of the genes, SsMYBS25-4, exhibited a significantly up-regulated expression in response to salt stress and was selected for further functional elucidation. It was found that the overexpression (OE) of SsMYBS25-4 in Arabidopsis can improve the salt stress tolerance of transgenic plants. Interestingly, the expression of some marker genes related to salt stress was significantly up-regulated in OE plants compared to wide-type plants. The SsMYB25-4 protein was localized in the nucleus and was proven to be directly bound to the promoter of the AtDR29B gene. We proposed a mechanism for SsMYB25-4 that enhances salt stress tolerance, contributing to the understanding and application of MYB-related genes in sugarcane breeding.

LcMYB43 enhances monoterpene biosynthesis by activating 1-deoxy-D-xylulose-5-phosphate synthase gene expression in Litsea cubeba

MYB transcription factors are crucial regulators involved in various metabolic processes in plants, including terpene biosynthesis. Litsea cubeba, a member of the Lauraceae family, is rich in monoterpenes and regulates their biosynthesis via the key enzyme DXS in the MEP pathway. Seven DXS genes have been identified in this species, but the role of the MYB family in terpene biosynthesis remains unclear. This study conducted a genome-wide characterization of the R2R3-MYB gene family in L. cubeba, analyzing its phylogenetics, expression, and regulatory functions. A total of 129 R2R3-MYB members were identified, with expansion mechanisms involving tandem and segmental duplications. Expression analysis revealed that LcMYB43 activates LcDXS5, a key enzyme in monoterpene biosynthesis. Overexpression of LcMYB43 significantly increased monoterpene accumulation. Y1H, EMSA, and dual-luciferase assays showed that LcMYB43 directly binds to the CAACAG motif in the LcDXS5 promoter, activating its expression. These findings suggest that LcMYB43 enhances monoterpene biosynthesis by promoting LcDXS5 expression, providing new insights into the regulatory mechanisms of monoterpene biosynthesis.

Identification of Nuclear Localization Sequence (NLS) Sites in R2R3-MYB Transcription Factor Involved in Anther Development

The R2R3-MYB family of transcription factors (TFs) plays a crucial role in cell specification and secondary metabolism regulation during plant development. In Arabidopsis, MS188, a typical R2R3-MYB protein, is essential for tapetal development and pollen wall formation. However, the nuclear localization sequence (NLS) responsible for directing MS188 into the nucleus has not been fully elucidated. In this study, the subcellular localization of the NLS-containing proteins was determined by GFP tagging in tobacco leaves, and three NLS regions within MS188 were identified: two located at the N-terminus of R2-MYB and one at the C-terminus of R3-MYB. We further narrowed the NLSs located at amino acids (AAs) 12-15, 18-22, and 96-107 via point mutation analysis. Combined with the cytoplasmic protein FBA6, these NLSs fusion proteins could localize in the nucleus. Importantly, the proteins with mutations in AAs 18-22 exhibited completely cytoplasmic signals, whereas other mutated sites partially abolished the nuclear signals. These findings suggest that the NLS at AAs 18-22 is sufficient for nuclear localization. To confirm the NLS functions in vivo, we constructed the vectors including the MS188 gene without the NLS sites, which failed to complement the male sterile phenotype of ms188. We also searched the highly conserved NLSs in other R2R3-MYB TFs and showed they are required for nuclear localization. Collectively, these findings revealed the specific NLS regions within R2R3-MYB transcription factors and highlighted their critical role for subcellular localization in plant developmental regulation.

CaMYBA-CaMYC-CaTTG1 complex activates the transcription of anthocyanin synthesis structural genes and regulates anthocyanin accumulation in pepper (Capsicum annuum L.) leaves

Anthocyanins are flavonoid-derived metabolites that contribute to plant and human health. At present, few studies have studied the biosynthesis and accumulation mechanism of anthocyanins in pepper leaves. The role of CaMYBA-CaMYC-CaTTG1 complex in anthocyanin biosynthesis in pepper leaves was studied. Yeast two-hybrid and dual-luciferase experiments showed that CaMYBA, CaMYC, and CaTTG1 could form an MYB-bHLH-WD40 (MBW) complex. They also have transcriptional activation on the anthocyanin synthesis structural genes CaCHS, CaCHI, CaF3H, CaF3'5'H, CaANS, CaDFR, and CaUFGT. Silencing CaMYBA or CaMYC could decrease the content of anthocyanin in pepper leaves. Transient overexpression of CaMYBA in tobacco indicated that CaMYBA determines the function of an MBW complex. Further analysis showed that CaMYBA could activate the expression of CaMYC by binding to its promoter. Overall, our study expands the understanding of the regulatory mechanism of anthocyanin synthesis in pepper leaves and has important significance for creating more pepper plants with different color patterns by gene editing engineering.

Systematic identification of R2R3-MYB S6 subfamily genes in Brassicaceae and its role in anthocyanin biosynthesis in Brassica crops

The Brassicaceae family includes Arabidopsis thaliana, various vegetables and oil crops. The R2R3-MYB genes of the S6 subfamily are crucial for regulating anthocyanin biosynthesis, however, their systematic identification in Brassicaceae plants is still incomplete. Here, we systematically identified homologous genes of R2R3-MYB transcription factors from the S6 subfamily across 31 Brassicaceae species. A total of 92 homologous genes were identified, with species representation ranging from 0 to 10 genes per species. Phylogenetic analysis classified these homologous genes into six distinct groups. Notably, approximately 70% of the homologous genes were found within the G6 group, indicating a high degree of evolutionary conservation. Furthermore, a phylogenetic analysis was conducted on 35 homologous genes obtained from six species within the U's triangle Brassica plants. The findings provided evidence of significant conservation among orthologous genes across species and demonstrated strong collinearity on subgenomic chromosomes, with notable tandem duplications observed on chromosomes A7 and C6. Subsequently, we predicted the cis-acting elements of these 35 homologous genes, and analyzed their structures, conserved motifs, and characteristic conserved domains, confirming the significant similarities between orthologous genes. Additionally, we employed white and purple flower rapeseed specimens to conduct qRT-PCR validation of the key genes and transcriptional regulators associated with the anthocyanin synthesis pathway. The results revealed significant differential expression of BnaPAP2.A7.b in purple flowers, alongside the differential expression of BnaPAP2.C6.d. Ultimately, based on previous research and the findings of this study, we propose a transcriptional regulatory framework to govern anthocyanin accumulation in distinct tissues or organs of B. napus. Our findings offer a novel perspective on the functional diversification of R2R3-MYB transcription factors within the S6 subfamily homologous genes, while also shedding light on the regulatory network governing anthocyanin biosynthesis in Brassicaceae species.

The Mutations in RcMYB114 Affect Anthocyanin Glycoside Accumulation in Rose

In plants, the R2R3-MYB transcription factors are one of the largest MYB gene families. These MYB transcription factors are very important for regulating plant growth and development. RcMYB114, RcbHLH, and RcWD40 promote anthocyanin accumulation by forming the MBW (MYB-bHLH-WD40) complex and determine the rose flower's color. RcMYB114 genomic sequences differ between the red petal and white varieties. Two non-synonymous substitutions were found in the open reading frame. It leads to a change in amino acids. Here, the anthocyanin content showed that there was no anthocyanin in white petals, while the anthocyanin content in red petals increased firstly at stage 2, decreased slightly at stage 4, and then increased again at stage 5. The spatiotemporal expression pattern analysis showed that RcMYB114 was not expressed in all petals and tissues of white petals at different flower development stages. In red petal varieties, RcMYB114 was highly expressed in petals, followed by styles, and not expressed in stems, young leaves, and stage 1 of flower development. However, RcMYB114 has the highest expression level at the blooming stage. The RcMYB114 sequence contains 9 SNPs in the coding region, 7 of which were synonymous substitutions that had no effect on the translation product and 2 of which were non-synonymous substitutions that resulted in amino acid alteration at positions 116 and 195, respectively. The RcMYB114 gene in red rose was named RcMYB114a, and in white rose was RcMYB114b. RcMYB114c was mutated into leucine via artificial mutation; it was valine at position 116 of RcMYB114a, and Glycine mutated into Arginine at position 195 of RcMYB114a was RcMYB114d. RcMYB114b was the double mutation at positions 116 and 195 of RcMYB114a. The results of yeast two-hybrid experiments showed that RcMYB114a and its missense mutations RcMYB114b, RcMYB114c, and RcMYB114d could both interact with RcbHLH and RcWD40 to form the MYB-bHLH-WD40 complex. A transient transformation experiment in tobacco confirmed that RcMYB114a and its missense mutations RcMYB114b, RcMYB114c, and RcMYB114d could significantly promote the high expression of related structural genes in tobacco, together with the RcbHLH gene, which led to the accumulation of anthocyanins and produced the red color of the leaves. The RcMYB114a gene and its missense mutations RcMYB114b, RcMYB114c, and RcMYB114d interacted with the RcbHLH gene and significantly regulated the accumulation of anthocyanins. The two non-synonymous mutations of RcMYB114 do not affect the function of the gene itself, but the content of the anthocyanins accumulated was different. This study should provide clues and references for further research on the molecular mechanism underlying the determination of rose petal color.

BcAMT1;2 interacts with BcLBD41 and BcMAMYB transcription factors during nitrogen metabolism in flowering Chinese cabbage

Chinese cabbage is an important vegetable in southern China. Excessive nitrogen fertilizer application can lead to the accumulation of nitrate in edible organs, which affects food value. Hence, the cultivation of varieties with high nitrogen utilization efficiency (NUE) and low nitrate accumulation is essential for molecular breeding. In flowering Chinese cabbage, Ammonium transporter 1;2 (AMT1;2,XM_009113156.2) significantly promotes plant growth, while reducing the nitrate content and ultimately improving the nutritional value of the crop; however, the exact underlying regulatory mechanisms remain unclear. Here, we aimed to investigate the response pattern of BcAMT1;2 to nitrogen (N) deficiency and mixed ammonium-nitrate nutrition and the potential roles played by its interacting proteins, Lateral organ boundaries domain 41 (LBD41,XM_009120072.3) and Membrane-anchored MYB (MAMYB,XM_009103351.3), in N metabolism. We found that transient silencing and overexpression of BcAMT1;2 regulated the absorption and accumulation of ammonium (NH4+) and nitrate (NO3-) in flowering Chinese cabbage. BcLBD41 may directly induce BcAMT1;2 expression, thereby regulating NH4+ accumulation in flowering Chinese cabbages. The expression of BcLBD41 and BcAMT1;2 were downregulated during N-deficiency and upregulated after NH4+ supply restoration. Overexpression of BcLBD41 in Arabidopsis improved root and shoot growth under both LA (low-ammonium; 0.25 mM NH4+) and A/Ni (ammonium [NH4+]: nitrate [NO3-]; 0.25 mM:0.75 mM) conditions by facilitating the expression of AtAMT1;2 in transgenic plants, leading to enhanced NH4+ uptake and accumulation. The BcMAMYB protein serves as a transmembrane protein and has a strong interaction with the BcAMT1;2 protein, as well as inducing the expression of the BcAMT1;2 promoter. In the OE-BcMAMYB strain, the expression of both BcMAMYB and BcAMT1;2 were repressed under N-deficiency conditions, whereas after silencing BcMAMYB, the expression of BcAMT1;2 was not induced by ammonium. Our findings contribute to a more profound understanding of the regulatory mechanisms responsible for nitrogen absorption and accumulation in relation to BcAMT1;2.

Heat-responsive MaHSF11 transcriptional activator positively regulates flavonol biosynthesis and flavonoid B-ring hydroxylation in banana (Musa acuminata)

Plant flavonols act primarily as ultraviolet radiation absorbers, reactive oxygen species scavengers, and phytoalexins, and they contribute to biotic and abiotic stress tolerance in plants. Banana (Musa acuminata), an herbaceous monocot and important fruit crop, accumulates flavonol derivatives in different organs, including the edible fruit pulp. Although flavonol content varies greatly in different organs, the molecular mechanisms involving transcriptional regulation of flavonol synthesis in banana are not known. Here, we characterized three SG7-R2R3 MYB transcription factors (MaMYBFA1, MaMYBFA2, and MaMYBFA3) and heat shock transcription factor (MaHSF11), to elucidate the molecular mechanism involved in transcriptional regulation of flavonol biosynthesis in banana. MaMYBFA positively regulates flavonol synthase 2 (MaFLS2) and downregulates MaFLS1. We show these transcription factors to be weak regulators of flavonol synthesis. Overexpression of MaHSF11 enhances flavonol contents, particularly that of myricetin, and promotes flavonol B-ring hydroxylation, which contributes to the diversity of flavonol derivatives. MaHSF11 directly interacts with the MaFLS1 and flavonoid 3',5'-hydroxylase1 (MaF3'5'H1) promoters, both in vitro and in vivo. MaHSF11 activates the expression of MaDREB1 directly, which is known to promote cold and chilling tolerance in banana fruit. Overall, our study elucidates a regulatory mechanism for flavonol synthesis in banana and suggests possible targets for genetic optimization to enhance nutritional value and stress responses in this globally important fruit crop.

Coding-Sequence Evolution Does Not Explain Divergence in Petal Anthocyanin Pigmentation Between Mimulus luteus Var luteus and M. l. variegatus

Biologists have long been interested in understanding genetic constraints on the evolution of development. For example, noncoding changes in a gene might be favored over coding changes if they are less constrained by pleiotropic effects. Here, we evaluate the importance of coding-sequence changes to the recent evolution of a novel anthocyanin pigmentation trait in the monkeyflower genus Mimulus. The magenta-flowered Mimulus luteus var. variegatus recently gained petal lobe anthocyanin pigmentation via a single-locus Mendelian difference from its sister taxon, the yellow-flowered M. l. luteus. Previous work showed that the differentially expressed transcription factor gene MYB5a/NEGAN is the single causal gene. However, it was not clear whether MYB5a coding-sequence evolution (in addition to the observed patterns of differential expression) might also have contributed to increased anthocyanin production in M. l. variegatus. Quantitative image analysis of tobacco leaves, transfected with MYB5a coding sequence from each taxon, revealed robust anthocyanin production driven by both alleles. Counter to expectations, significantly higher anthocyanin production was driven by the allele from the low-anthocyanin M. l. luteus, a result that was confirmed through both a replication of the initial study and analysis by an alternative method of spectrophotometry on extracted leaf anthocyanins. Together with previously published expression studies, our findings support the hypothesis that petal pigment in M. l. variegatus was not gained by protein-coding changes, but instead solely via noncoding cis-regulatory evolution. Finally, while constructing the transgenes needed for this experiment, we unexpectedly discovered two sites in MYB5a that appear to be post-transcriptionally edited-a phenomenon that has been rarely reported, and even less often explored, for nuclear-encoded plant mRNAs.

Spatial transcriptome and single-cell RNA sequencing reveal the molecular basis of cotton fiber initiation development

Recent advances in single-cell transcriptomics have greatly expanded our knowledge of plant development and cellular responses. However, analyzing fiber cell differentiation in plants, particularly in cotton, remains a complex challenge. A spatial transcriptomic map of ovule from -1 DPA, 0 DPA, and 1 DPA in cotton was successfully constructed, which helps to explain the important role of sucrose synthesis and lipid metabolism during early fiber development. Additionally, single-cell RNA sequencing (scRNA-seq) further highlighted the cellular heterogeneity and identified clusters of fiber developmental marker genes. Integration of spatial and scRNA-seq data unveiled key genes SVB and SVBL involved in fiber initiation, suggesting functional redundancy between them. These findings provide a detailed molecular landscape of cotton fiber development, offering valuable insights for enhancing lint yield.

An R2R3-type MYB transcription factor, GmMYB77, negatively regulates isoflavone accumulation in soybean [Glycine max (L.) Merr.]

Soybean [Glycine max (L.) Merr.] is an exceptionally rich in isoflavones, and these compounds attach to oestrogen receptors in the human body, lessening the risk of breast cancer and effectively alleviating menopausal syndrome symptoms. Uncovering the molecular mechanisms that regulate soybean isoflavone accumulation is crucial for enhancing the production of these compounds. In this study, we combined bulk segregant analysis sequencing (BSA-seq) and a genome-wide association study (GWAS) to discover a novel R2R3-MYB family gene, GmMYB77, that regulates isoflavone accumulation in soybean. Using the soybean hairy root transient expression system, we verified that GmMYB77 inhibits isoflavone accumulation. Furthermore, knocking out GmMYB77 significantly increased total isoflavone (TIF) content, particularly malonylglycitin, while its overexpression resulted in a notable decrease in contents of malonylglycitin and TIF. We found that GmMYB77 can directly binds the core sequence GGT and suppresses the expression of the key isoflavone biosynthesis genes Isoflavone synthase 1 (GmIFS1), Isoflavone synthase 2 (GmIFS2), Chalcone synthase 7 (GmCHS7) and Chalcone synthase 8 (GmCHS8) by using dual-luciferase assays, electrophoretic mobility shift assays and yeast one-hybrid experiments. Natural variations in the promoter region of GmMYB77 affect its expression, thereby regulating the malonylglycitin and TIF contents. Hap-P2, an elite haplotype, plays a pivotal role in soybean breeding for substantially enhanced isoflavone content. These findings enhance our understanding of the genes influencing soybean isoflavone content and provide a valuable genetic resource for molecular breeding efforts in the future.

Diverse roles of MYB transcription factors in plants

MYB transcription factors (TFs), one of the largest TF families in plants, are involved in various plant-specific processes as the central regulators, such as in phenylpropanoid metabolism, cell cycle, formation of root hair and trichome, phytohormones responses, reproductive growth and abiotic or biotic stress responses. Here we summarized multiple roles and explained the molecular mechanisms of MYB TFs in plant development and stress adaptation. The exploration of MYB TFs contributes to a better comprehension of molecular regulation in plant development and environmental adaptability.

Phase separation of MYB73 regulates seed oil biosynthesis in Arabidopsis

MYB family transcription factors (TFs) play crucial roles in plant development, metabolism, and responses to various stresses. However, whether MYB TFs are involved in regulating fatty acid biosynthesis in seeds remains largely elusive. Here, we demonstrated that transgenic Arabidopsis (Arabidopsis thaliana) plants overexpressing MYB73 exhibit altered FATTY ACID ELONGATION1 (FAE1) expression, seed oil content, and seed fatty acid composition. Electrophoretic mobility shift assays showed that FAE1 is a direct target of MYB73, and functional assays revealed that MYB73 represses FAE1 promoter activity. Transcriptomic analysis of the MYB73-overexpressing plants detected significant changes in the expression of genes involved in fatty acid biosynthesis and triacylglycerol assembly. Furthermore, MYB73 expression was responsive to abscisic acid (ABA), and ABA-responsive element binding factor 2 directly bound to the ABA-responsive element in the MYB73 promoter to activate its expression. Additionally, we determined that MYB73 exhibits the hallmarks of an intrinsically disordered protein and forms phase-separated condensates with liquid-like characteristics, which are important in regulating target gene expression. Together, our findings suggest that MYB73 condensate formation likely fine-tunes seed oil biosynthesis.

The transcription factor VvMYB44-1 plays a role in reducing grapevine anthocyanin biosynthesis at high temperature

High temperature reduces anthocyanin accumulation in various horticultural plants. However, the molecular mechanisms underlying the high-temperature-induced reduction of anthocyanin in grape (Vitis vinifera) remain poorly understood. In this study, VvMYB44-1 was identified as a transcriptional repressor of anthocyanin biosynthesis in grape berries, and its gene expression was strongly induced by high-temperature treatment. Overexpression of VvMYB44-1 inhibited anthocyanin accumulation in both grape berries and tobacco (Nicotiana tabacum) by repressing the transcription of the anthocyanin biosynthesis genes dihydroflavonol-4-reductase (VvDFR) and UDP-glucose flavonoid-3-O-glucosyltransferase (VvUFGT). Furthermore, the interaction between VvMYB44-1 and VvWDR2 competitively inhibited the formation of the MYB-bHLH-WD40 (MBW) activation complex and weakened the transcriptional activity of the complex, thereby decreasing anthocyanin accumulation. Additionally, VvMYB44-1 facilitated cytokinin (CK) accumulation by upregulating the expression of the CK synthesis gene lonely guy 8 (VvLOG8) and inhibiting the CK degradation gene CK oxidase 4(VvCKX4), thus contributing to CK-mediated anthocyanin inhibition in grape berries. Moreover, the inhibitory effect of VvMYB44-1 on anthocyanin biosynthesis and its downstream target genes was weakened with the deletion of the ethylene-responsive element binding factor-associated amphiphilic repression (EAR) motif, indicating that the EAR motif is indispensable for the inhibitory effect of VvMYB44-1 on anthocyanin biosynthesis in grapes. These results provide insights into the regulatory network of VvMYB44-1 in high-temperature-mediated anthocyanin biosynthesis in grapes.

Integrated metabolome and transcriptome analysis provides insights into the mechanisms of terpenoid biosynthesis in tea plants (Camellia sinensis)

Volatile terpenoids are major substances responsible for the floral and fruity scents of teas. However, little is known about the regulatory mechanisms of terpenoid biosynthesis pathways in tea plants. 'Zhenfeng Yesheng tea' (ZFYS), a distinctive tea tree germplasm resource in Guizhou province, is known for its unique flavor characterized by a mellow taste and a floral aroma. Here, we conducted metabolome and transcriptome analyses of 'ZFYS', 'Jinguanyin tea' (JGY), and 'Longjing 43 tea' (LJ43) leaves to obtain the global correlation of MYB TFs with terpene synthase (TPS) genes and differential accumulated metabolites. In total, 292 differentially accumulated metabolites (DAMs) were identified and chemically classified, with 26.37% of them being terpenoids. Among these, 33 key volatile terpenoids significantly accumulated in 'ZFYS', 'LJ43', and 'JGY' leaves, mainly contributing to the floral and sweet scents. In addition, a total of 6330, 7238, and 8557 unigenes were obtained in "JGY vs LJ43", "ZFYS vs JGY", and "ZFYS vs LJ43" comparisons, respectively. The results of transcriptome analysis, correlation analysis, and quantitative real-time PCR (qRT-PCR) analysis revealed significant correlations between candidate CsTPSs and CsMYBs. The expression levels of CsMYB59, CsMYB167 and CsMYB178 showed that they had a strong positive correlation with CsTPS01, -03, -15, -53, -69 and -79, suggesting their potential function in regulating sesquiterpenoid biosynthesis. In conclusion, this study provides comprehensive metabolomics and transcriptomics profiles of the germplasm of 'ZFYS' tea plants and reveals the underlying key genes involved in volatile terpenoid biosynthesis.

MYB proteins: Versatile regulators of plant development, stress responses, and secondary metabolite biosynthetic pathways

MYB proteins are ubiquitous in nature, regulating key aspects of plant growth and development. Although MYB proteins are known for regulating genes involved in secondary metabolite biosynthesis, particularly phenylpropanoids, their roles in terpenoid, glucosinolate, and alkaloid biosynthesis remain less understood. This review explores the structural and functional differences between activator and repressor MYB proteins along with their roles in plant growth, development, stress responses, and secondary metabolite production. MYB proteins serve as central hubs in protein-protein interaction networks that regulate expression of numerous genes involved in the adaptation of plants to varying environmental conditions. Thus, we also highlight key interacting partners of MYB proteins and their roles in these adaptation mechanisms. We further discuss the mechanisms regulating MYB proteins, including autoregulation, epigenetics, and post-transcriptional and post-translational modifications. Overall, we propose MYB proteins as versatile regulators for improving plant traits, stress responses, and secondary metabolite production.

A genus-specific R2R3 MYB transcription factor, CsMYB34, regulates galloylated catechin biosynthesis in Camellia sinensis

Galloylated catechins are the dominant polyphenols in Camellia sinensis (L.) O. Kuntze. The mechanisms responsible for accumulation of these specialized metabolites in tea plants remains unclear. This paper presents an extended member of subgroup 5 of transcription factors R2R3-MYB, CsMYB34, as a critical gene specifically regulating galloylated catechin biosynthesis. CsMYB34 has a TT2-type motif [VIRTKATRCSKVFIP]. Its transcription levels were positively correlated with galloylated catechin content in 19 tea varieties, with correlation coefficients ≥0.79. Suppression of CsMYB34 expression caused a significant decrease in galloylated catechin content, as well as reduced expression levels of the key galloylated catechin biosynthesis gene CsSCPL4. Yeast one-hybrid (Y1H), electrophoretic mobile shift assay (EMSA) and dual-luciferase reporter system (DLR) showed that CsMYB34 interacts directly with the promoter region of CsSCPL4, thereby upregulating its transcription. This research indicates that the CsMYB34 transcription factor selectively modulates the biosynthetic pathway of galloylated catechins, thereby offering a plausible rationale for the observed elevated levels of these compounds in tea leaves.

Identification of R2R3-MYB Transcription Factor Family Based on Amaranthus tricolor Genome and AtrMYB72 Promoting Betalain Biosynthesis by Directly Activating AtrCYP76AD1 Expression

MYB (myeloblastosis) is one of the most abundant transcription factors in plants which regulates various biological processes. The molecular characteristics and function of R2R3-MYB transcription factors in amaranth remain unclear. In this study, 73 R2R3-MYB members were identified from the amaranth genome database and we further analyzed their chromosome position, conserved motifs, physiological and biochemical features, collinearity relationships, gene structure, phylogeny and cis-acting element. Based on the phylogenetic and expression pattern analysis, 14 candidate R2R3-MYB genes might be involved in the betalain synthesis. Amongst the 14 candidate R2R3-MYB genes, the expression level of AtrMYB72 was higher in 'Suxian No.1' than 'Suxian No.2', and also higher in the red section than in the green section of the same leaf in Amaranthus. The overexpression vector pCambia1301-AtrMYB72-GUS and VIGS (virus-induced gene silencing) vector pTRV2- AtrMYB72 were transferred into leaves of 'Suxian No.1' via an Agrobacterium-mediated method. The results showed that AtrMYB72 overexpression could promote betalain synthesis. A yeast one-hybrid assay and dual luciferase reporter gene assay demonstrated that AtrMYB72 could bind to the AtrCYP76AD1 promoter to promote betalain synthesis. These results indicated that AtrMYB72 promoted betalain biosynthesis in amaranth by activating the AtrCYP76AD1 transcription. Our results could provide new insights into the betalain biosynthesis in amaranth.

Regulation of Flavonoid Biosynthesis by the MYB-bHLH-WDR (MBW) Complex in Plants and Its Specific Features in Cereals

Flavonoids are a large group of secondary metabolites, which are responsible for pigmentation, signaling, protection from unfavorable environmental conditions, and other important functions, as well as providing numerous benefits for human health. Various stages of flavonoid biosynthesis are subject to complex regulation by three groups of transcription regulators-MYC-like bHLH, R2R3-MYB and WDR which form the MBW regulatory complex. We attempt to cover the main aspects of this intriguing regulatory system in plants, as well as to summarize information on their distinctive features in cereals. Published data revealed the following perspectives for further research: (1) In cereals, a large number of paralogs of MYC and MYB transcription factors are present, and their diversification has led to spatial and biochemical specialization, providing an opportunity to fine-tune the distribution and composition of flavonoid compounds; (2) Regulatory systems formed by MBW proteins in cereals possess distinctive features that are not yet fully understood and require further investigation; (3) Non-classical MB-EMSY-like complexes, WDR-independent MB complexes, and solely acting R2R3-MYB transcription factors are of particular interest for studying unique regulatory mechanisms in plants. More comprehensive understanding of flavonoid biosynthesis regulation will allow us to develop cereal varieties with the required flavonoid content and spatial distribution.

PbMYB5 transcription factor plays a role in regulating anthocyanin biosynthesis in pear (Pyrus bretschneideri Rehd) skin

The phenylacetone pathway, which encompasses flavonoids, lignin, and other compounds, is of paramount importance in determining the quality of pear fruit. Nevertheless, the precise regulatory functions of R2R3-MYB transcription factors in the metabolic pathways that regulate pear color changes remain unclear. In this study, we isolated an R2R3-PbMYB5(PbMYB5) transcription factor from 'Red Zaosu' pears and demonstrated that it influenced the expression of several genes, including PbCAD1, PbF5H, PbLAR, PbANR, and PbUFGT. The overexpression of PbMYB5 resulted in a notable elevation in anthocyanin concentration within the pear epidermis. Further research has shown that PbMYB5 is able to bind to PbANS and also has interactions with PbbHLH3 and PbbHLH33.We proposed that PbMYB5 forms a complex with PbbHLH3, PbbHLH33, and PbWD40 to activate PbANS and promote anthocyanin accumulation. This study offers new insights into the regulation of various metabolic pathways that impact fruit coloration.

Epibrassinolide Regulates Lhcb5 Expression Though the Transcription Factor of MYBR17 in Maize

Photosynthesis, which is the foundation of crop growth and development, is accompanied by complex transcriptional regulatory mechanisms. Research has established that brassinosteroids (BRs) play a role in regulating plant photosynthesis, with the majority of research focusing on the physiological level and regulation of rate-limiting enzymes in the dark reactions of photosynthesis. However, studies on their effects on maize photosynthesis, specifically on light-harvesting antenna proteins, have yet to be conducted. The peripheral light-harvesting antenna protein Lhcb5 is crucial for capturing and dissipating light energy. Herein, by analyzing the transcriptomic data of maize seedling leaves treated with 24-epibrassinolide (EBR) and verifying them using qPCR experiments, we found that the MYBR17 transcription factor may regulate the expression of the photosynthetic light-harvesting antenna protein gene. Further experiments using protoplast transient expression and yeast one-hybrid tests showed that the maize transcription factor MYBR17 responds to EBR signals and binds to the promoter of the light-harvesting antenna protein Lhcb5, thereby upregulating its expression. These results were validated using an Arabidopsis mybr17 mutant. Our results offer a theoretical foundation for the application of BRs to enhance the photosynthetic efficiency of maize.

In-silico analysis and transformation of OsMYB48 transcription factor driven by CaMV35S promoter in model plant - Nicotiana tabacum L. conferring abiotic stress tolerance

Global crop yield has been affected by a number of abiotic stresses. Heat, salinity, and drought stress are at the top of the list as serious environmental growth-limiting factors. To enhance crop productivity, molecular approaches have been used to determine the key regulators affecting stress-related phenomena. MYB transcription factors (TF) have been reported as one of the promising defensive proteins against the unfavorable conditions that plants must face. Different roles of MYB TFs have been suggested such as regulation of cellular growth and differentiation, hormonal signaling, mediating abiotic stress responses, etc. To gain significant insights, a comprehensive in-silico analysis of OsMYB TF was carried out in comparison with 21 dicot MYB TFs and 10 monocot MYB TFs. Their chromosomal location, gene structure, protein domain, and motifs were analyzed. The phylogenetic relationship was also studied, which resulted in the classification of proteins into four basic groups: groups A, B, C, and D. The protein motif analysis identified several conserved sequences responsible for cellular activities. The gene structure analysis suggested that proteins that were present in the same class, showed similar intron-exon structures. Promoter analysis revealed major cis-acting elements that were found to be responsible for hormonal signaling and initiating a response to abiotic stress and light-induced mechanisms. The transformation of OsMYB TF into tobacco was carried out using the Agrobacterium-mediated transformation method, to further analyze the expression level of a gene in different plant parts, under stress conditions. To summarize, the current studies shed light on the evolution and role of OsMYB TF in plants. Future investigations should focus on elucidating the functional roles of MYB transcription factors in abiotic stress tolerance through targeted genetic modification and CRISPR/Cas9-mediated genome editing. The application of omics approaches and systems biology will be indispensable in delineating the regulatory networks orchestrated by MYB TFs, facilitating the development of crop genotypes with enhanced resilience to environmental stressors. Rigorous field validation of these genetically engineered or edited crops is imperative to ascertain their utility in promoting sustainable agricultural practices.

Rosa rugosa R2R3-MYB transcription factors RrMYB12 and RrMYB111 regulate the accumulation of flavonols and anthocyanins

Roses (Rosa rugosa) are a famous flower with high ornamental and economic value. But the petals of roses are usually pink and purple, which restricted its application in garden settings. Flavonols and anthocyanins are crucial secondary metabolites related to flower pigmentation in plants. While MYB transcription factors involved in the biosynthesis pathway of anthocyanins have been identified in roses, the functional characterization of the MYB transcription factor regulating flavonol synthesis in R. rugosa remains unexplored. In this study, we isolated and characterized the R2R3-MYB transcription factors RrMYB12 and RrMYB111 involved in regulation of the flavonol biosynthetic pathway from R. rugosa. The bioinformatics analysis indicated that both the RrMYB12 and RrMYB111 belong to the R2R3-MYB subgroup 7 family. qRT-PCR analysis showed that RrMYB12 and RrMYB111 were expressed at low levels in roots and flowers. And transactivation activity assay indicated that RrMYB12 and RrMYB111 were transcriptional activators. The overexpression of RrMYB12 and RrMYB111 in tobacco resulted in an elevation of flavonol levels and a reduction in anthocyanin levels in flowers due to the upregulation of structural genes involved in flavonol synthesis, while the biosynthesis genes for the anthocyanin pathway were significantly downregulated. The transient reporter assay demonstrated that RrMYB12 exhibited strong activation of the promoters of RrCHS and RrFLS in Nicotiana benthamiana leaves following transient transformation. Furthermore, it was observed that RrMYBs displayed binding specificity to the promoter region of CsFLS.The functional characterization of the flavonol synthesis regulatory factors RrMYB12 and RrMYB111 offers a deeper understanding of the regulatory mechanism governing flavonol biosynthesis in roses, while also presenting an effective tool for genetic manipulation aimed at creating new varieties.

MYB transcription factors in Peucedanum Praeruptorum Dunn: the diverse roles of the R2R3-MYB subfamily in mediating coumarin biosynthesis

BACKGROUND

The MYB superfamily (v-myb avian myeloblastosis viral oncogene homolog) plays a role in plant growth and development, environmental stress defense, and synthesis of secondary metabolites. Little is known about the regulatory function of MYB genes in Peucedanum praeruptorum Dunn, although many MYB family members, especially R2R3-MYB genes, have been extensively studied in model plants.

RESULTS

A total of 157 R2R3-MYB transcription factors from P. praeruptorum were identified using bioinformatics analysis. Comprehensive analyses including chromosome location, microsynteny, gene structure, conserved motif, phylogenetic tree, and conserved domain were further performed. The length of the 157 transcription factors ranged from 120 to 1,688 amino acids (molecular weight between 14.21 and 182.69 kDa). All proteins were hydrophilic. Subcellular localization predictions showed that 155 PpMYB proteins were localized in the nucleus, with PpMYB12 and PpMYB157 localized in the chloroplasts and mitochondria, respectively. Ten conserved motifs were identified in the PpMYBs, all of which contained typical MYB domains. Transcriptome analysis identified 47,902 unigenes. Kyoto Encyclopedia of Genes and Genomes analysis revealed 136 pathways, of which 524 genes were associated with the phenylpropanoid pathway. Differential expressed genes (DEGs) before and after bolting showed that 11 genes were enriched in the phenylpropanoid pathway. Moreover, the expression patterns of transcription genes were further verified by qRT-PCR. With high-performance liquid chromatography (HPLC), 8 coumarins were quantified from the root, stem, and leaf tissue samples of P. praeruptorum at different stages. Praeruptorin A was found in both roots and leaves before bolting, whereas praeruptorin B was mainly concentrated in the roots, and the content of both decreased in the roots and stems after bolting. Praeruptorin E content was highest in the leaves and increased with plant growth. The correlation analysis between transcription factors and coumarin content showed that the expression patterns of PpMYB3 and PpMYB103 in roots align with the accumulation trends of praeruptorin A, praeruptorin B, praeruptorin E, scopoletin, and isoscopoletin, which declined in content after bolting, suggesting that these genes may positively regulate the biosynthesis of coumarins. Eleven distinct metabolites and 48 DEGs were identified. Correlation analysis revealed that the expression of all DEGs were significantly related to the accumulation of coumarin metabolites, indicating that these genes are involved in the regulation of coumarin biosynthesis.

CONCLUSIONS

R2R3-MYB transcription factors may be involved in the synthesis of coumarin. Our findings provide basic data and a rationale for future an in-depth studies on the role of R2R3-MYB transcription factors in the growth and regulation of coumarin synthesis.

Tae-miR396b regulates TaGRFs in spikes of three wheat spike mutants

Tillering and spike differentiation are key agronomic traits for wheat (Triticum aestivum L.) production. Numerous studies have shown that miR396 and growth-regulating factor genes (GRFs) are involved in growth and development of different plant organs. Previously, we have reported that wheat miR396b (tae-miR396b) and their targets TaGRFs (T. aestivum GRFs) play important roles in regulating wheat tillering. This study was to investigate the regulatory roles of tae-miR396b and TaGRFs played during wheat spike development. Wheat cultivar Guomai 301 (wild type, WT) and its three sipke mutants dwarf round spike mutant (drs), apical spikelet sterility mutant (ass) and prematurely terminated spike differentiation mutant (ptsd1) were studied. Three homeologous genes of tae-miR396b on the long arms of chromosomes 6A, 6B, and 6D were identified, and they encoded the same mature miRNA. Complementary sequences of mature tae-miR396b were identified in 23 TaGRFs, indicating they were the target genes of tae-miR396b. Tae-miR396b had different regulatory effects on TaGRFs between Guomai 301 and its mutants. TaGRF2-7A was confirmed to be the target gene of tae-miR396b by molecular interaction assay. The expression levels of tae-miR396b and TaGRFs were different between WT and mutants drs, ass and ptsd1 at the floret primordium visible (S1), the two awns/spikelet reaching apical meristem of the spikelet (S2), and the green anther stage (S3). The expression level of tae-miR396b in WT was significantly higher than that in mutants drs and ass. The most TaGRFs were negatively regulated by tae-miR396b. The abnormal expressions of TaGRF1 (6A, 6D), TaGRF2 (7A, 7B, 7D), TaGRF4 (6A, 6B), TaGRF5 (4A, 7A, 7D), and TaGRF10 (6A, 6B, 6D) were important causes for abnormal spike development in the three mutants. This study laid foundation for further elucidating functions of tae-miR396b and TaGRFs underlying wheat spike development. Regulating tae-miR396b and TaGRFs will be a new approach for wheat high yield breeding.

Evolutionary trajectory of transcription factors and selection of targets for metabolic engineering

Transcription factors (TFs) provide potentially powerful tools for plant metabolic engineering as they often control multiple genes in a metabolic pathway. However, selecting the best TF for a particular pathway has been challenging, and the selection often relies significantly on phylogenetic relationships. Here, we offer examples where evolutionary relationships have facilitated the selection of the suitable TFs, alongside situations where such relationships are misleading from the perspective of metabolic engineering. We argue that the evolutionary trajectory of a particular TF might be a better indicator than protein sequence homology alone in helping decide the best targets for plant metabolic engineering efforts. This article is part of the theme issue 'The evolution of plant metabolism'.

Functional identification of AaMYB113 and AaMYB114 from Aeonium arboreum 'Halloween' in model plants

Aeonium arboreum 'Halloween', a popular indoor ornamental succulent in China, changes its leaf colour to red on light exposure. However, the underlying molecular mechanisms is still vague. Comparative analysis of transcriptome data from 'Halloween' leaves treated under dark and light conditions revealed two R2R3-MYB transcription factors, AaMYB113 and AaMYB114, that may mediate anthocyanin accumulation. In this study, we cloned the AaMYB113 and AaMYB114 genes, encoding proteins of 279 and 248 amino acids, respectively. Transcriptional activity analysis revealed that AaMYB113 exhibits strong transcriptional activity, in contrast to AaMYB114, which demonstrates minimal activity. Transient expression studies in tobacco leaves demonstrated that AaMYB113 induced red pigmentation, whereas AaMYB114 did not. Subsequent stable overexpression in Arabidopsis thaliana confirmed that AaMYB113, but not AaMYB114, could similarly turn Arabidopsis leaves red. Further stable transformation of AaMYB113 in tobacco affected multiple floral components, including leaves, petals, calyx, flower tubes, and filaments, turning them red. Quantitative real-time PCR (qRT-PCR) assay in leaves of AaMYB113 stably transformed tobacco and Arabidopsis revealed upregulation of anthocyanin biosynthesis-related structural genes and TT8-like transcription factors. Moreover, the dual luciferase analysis confirmed that AaMYB113 can activate the promoters of 'Halloween' anthocyanin synthesis structural genes, AaCHS, AaCHI, AaF3H, AaDFR and AaANS. The above results indicate that AaMYB113 can promote anthocyanin synthesis, while AaMYB114 does not have this function. This study contributes significantly to the limited body of research on the molecular mechanisms of anthocyanin synthesis in succulents, advancing our understanding of how these pathways are regulated in 'Halloween' succulents and potentially other species.

Genome-Wide Analysis of the Common Fig (Ficus carica L.) R2R3-MYB Genes Reveals Their Structure, Evolution, and Roles in Fruit Color Variation

The R2R3-MYB transcription factor (TF) family is crucial for regulating plant growth, stress response, and fruit ripening. Although this TF family has been examined in a multitude of plants, the R2R3-MYB TFs in Ficus carica, a Mediterranean fruit species, have yet to be characterized. This study identified and classified 63 R2R3-MYB genes (FcMYB1 to FcMYB63) in the F. carica genome. We analyzed these genes for physicochemical properties, conserved motifs, phylogenetic relationships, gene architecture, selection pressure, and gene expression profiles and networks. The genes were classified into 29 clades, with members of the same clade showing similar exon-intron structures and motif compositions. Of the 54 orthologous gene pairs shared with mulberry (Morus notabilis), 52 evolved under negative selection, while two pairs (FcMYB55/MnMYB20 and FcMYB59/MnMYB31) experienced diversifying selection. RNA-Seq analysis showed that FcMYB26, FcMYB33, and FcMYB34 were significantly overexpressed in fig fruit peel during maturation phase III. Weighted gene co-expression network analysis (WGCNA) indicated that these genes are part of an expression module associated with the anthocyanin pathway. RT-qPCR validation confirmed these findings and revealed that the Tunisian cultivars 'Zidi' and 'Soltani' have cultivar-specific R2R3-FcMYB genes highly overexpressed during the final stage of fruit maturation and color acquisition. These genes likely influence cultivar-specific pigment synthesis. This study provides a comprehensive overview of the R2R3-MYB TF family in fig, offering a framework for selecting genes related to fruit peel color in breeding programs.

Identification and Characterization of EIN3/EIL Transcription Factor Family Members in Pinus massoniana Lamb

Transcription factors refer to types of proteins that perform significant functions in the process of gene expression regulation. The ethylene insensitive 3/ethylene insensitive 3-like (EIN3/EIL) family, functioning as significant transcription factors regulating ethylene, plays a critical role in the growth and development of plants and participates in the plant's response to diverse environmental stresses. Pinus massoniana is an excellent native tree with high economic and ecological value. However, the study of EIN3/EIL genes in gymnosperms, for instance, P. massoniana, is still relatively limited. In this research, four putative EIN3/EIL genes were identified in the transcriptome of P. massoniana. Bioinformatics analysis showed that PmEIL genes contain a highly conserved EIN3 domain and other structural features of acidic, proline-rich and glutamine-rich sites. The molecular evolution tree analysis demonstrated that the EIN3/EIL family was partitioned into three categories (A, B, and C), and the number, type, and distribution of conserved motifs grouped in one category were similar. The results of qRT-PCR indicated that the expression levels of PmEIL genes were markedly elevated in needles compared to other tissues. Through the analysis of expression patterns of the PmEIL genes under various stress treatments, it was found that the PmEIL genes could participate in plant hormone stimulation induction, osmosis, drought and other response processes. In addition, PmEIL is a nuclear localization protein. PmEIL1, PmEIL3, and PmEIL4 are transcriptional activators, while PmEIL2 is a transcriptional suppressor. This research provides a basis for further elucidating the function of EIN3/EIL transcription factors in growth, development and stress response of P. massoniana.

Genome-wide investigation of MYB gene family in Areca catechu and potential roles of AcTDF in transgenic Arabidopsis

BACKGROUND

MYB protein, a crucial transcription factor, holds crucial importance in plant growth, development, stress responses, and secondary metabolite regulation. While MYB proteins have been extensively studied, research on MYBs within the palm family, particularly in Areca catechu, remains limited.

METHODS AND RESULTS

This study identified 259 MYB genes in Areca catechu, including 105 1R-MYBs, 150 R2R3-MYBs, 3 3R-MYBs, and 1 4R-MYBs. Physicochemical properties, collinearity, and gene structure of these genes were analyzed. The AcMYB is distributed across 16 chromosomes of A.catechu and has 119 and 195 homologs in Arabidopsis and rice, respectively. Cis-acting elements in the promoter region suggest roles in plant hormones, growth, development, and stress. R2R3-MYB genes were divided into eight groups based on tissue expression profiles. The flowering-related gene AcTDF is highly expressed in male flowers. Overexpression of AcTDF in Arabidopsis promotes early flowering, upregulates AtSOC1 and AtFUL, and enhances tolerance to drought and salt stress.

CONCLUSIONS

These results provide valuable insights for the identification and analysis of the MYB gene family in Areca catechu and offer a basis for the subsequent verification of its related functions and the role and significance of its role in the evolution of palms.

In silico analysis of R2R3-MYB transcription factors in the basal eudicot model, Aquilegia coerulea

R2R3-MYBs are an important group of transcription factors that regulate crucial developmental processes across the plant kingdom; yet no comprehensive analysis of the R2R3-MYBs in the early-diverging eudicot clade of Ranunculaceae has been conducted so far. In the present study, Aquilegia coerulea is chosen to understand the extent of conservation and divergence of R2R3-MYBs as a representative of the family by analysing the genomic distribution, organization, gene structure, physiochemical properties, protein architecture, evolution and possible mode of expansion. Genome-wide analysis showed the presence of 82 putative homologues classified into 21 subgroups, based on phylogenetic analysis of full-length protein sequences. The domain has remained largely conserved across all homologues with few differences from the characterized Arabidopsis thaliana R2R3-MYBs. The topology of the phylogenetic tree remains the same when full-length protein sequences are used, indicating that the evolution of R2R3-MYBs is driven by the domain region only. This is supported by the presence of similar structures of exon-intron and conserved motifs within the same subgroup. Furthermore, comparisons of the AqcoeR2R3-MYB members with monocots and core-eudicots revealed the evolutionary expansion of a few functional clades, such as A. thaliana R2R3-MYB subgroup 6 (SG6), the upstream regulatory factors of floral pigment biosynthesis and floral color. The reconstructed evolutionary history of SG6-like genes across angiosperms highlights the occurrence of independent duplication events in the genus Aquilegia. AqcoeR2R3-MYB genes are present in all seven chromosomes of A. coerulea, most of which result from local and segmental duplications. Selection analysis of these duplicated gene pairs indicates purifying selection except one, and the physiochemical analyses of R2R3-MYBs reveal differences among the MYBs signifying their functional diversification. This study paves the way for further investigation of paralogous copies and their probable role in the evolution of different floral traits in A. coerulea. It lays the foundation for functional genomic studies of R2R3-MYBs in the basal eudicots and facilitates comparative studies among angiosperms. The work also provides a framework for deciphering novel genetic regulatory pathways that govern the diversity of floral morphology.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-024-04119-y.

Genome-wide identification of R2R3-MYB transcription factors in Betula platyphylla and functional analysis of BpMYB95 in salt tolerance

The Myeloblastosis (MYB) transcription factor (TF) family is one of the largest transcription factor families in plants and plays an important role in various physiological processes. At present, there are few reports on birch (Betula platyphylla Suk.) of R2R3-MYB-TFs, and most BpMYBs still need to be characterized. In this study, 111 R2R3-MYB-TFs with conserved R2 and R3 MYB domains were identified. Phylogenetic tree analysis showed that the MYB family members of Arabidopsis thaliana and birch were divided into 23 and 21 subgroups, respectively. The latter exhibited an uneven distribution across 14 chromosomes. There were five tandem duplication events and 17 segmental duplication events between BpMYBs, and repeat events play an important role in the expansion of the family. In addition, the promoter region of MYBs was rich in various cis-acting elements, and MYB-TFs were involved in plant growth and development, light responses, biotic stress, and abiotic stress. RNA-sequencing (RNA-seq) and quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) results revealed that most R2R3-MYB-TFs in birch responded to salt stress. In particular, the expression of BpMYBs in the S20 subfamily was significantly induced by salt, drought, abscisic acid, and methyl jasmonate stresses. Based on the weighted co-expression network analysis of physiological and RNA-seq data of birch under salt stress, a key MYB-TF BpMYB95 (BPChr12G24087), was identified in response to salt stress, and its expression level was induced by salt stress. BpMYB95 is a nuclear localization protein with transcriptional activation activity in yeast and overexpression of this gene significantly enhanced salt tolerance in Saccharomyces cerevisiae. The qRT-PCR and histochemical staining results showed that BpMYB95 exhibited the highest expression in the roots, young leaves, and petioles of birch plants. Overexpression of BpMYB95 significantly improved salt-induced browning and wilting symptoms in birch leaves and alleviated the degree of PSII photoinhibition caused by salt stress in birch seedlings. In conclusion, most R2R3-MYB-TFs found in birch were involved in the salt stress response mechanisms. Among these, BpMYB95 was a key regulatory factor that significantly enhanced salt tolerance in birch. The findings of this study provide valuable genetic resources for the development of salt-tolerant birch varieties.

Characterization and functions of Myeloblastosis (MYB) transcription factors in cucurbit crops

Myeloblastosis (MYB) is one of the largest family of transcription factors (TFs) in plants. It plays a key role in plant life activities, such as metabolic regulation, stress resistant, as well as helpful for plant growth and development. In China, cucurbit is an important and nutrients rich vegetable crop, which have high medicinal and socio-economic values. In this review, we discussed the structure and characterization of MYB TFs and how do regulate flower development, fruit maturity, fruit quality, and flavonoid biosynthesis. Furthermore, we highlight the effect and contribution of MYB TFs in the regulation of biotic and abiotic stress resistance. This comprehensive review will provide a new reference for the more effective application of MYB TF in quality control, stress resistance research and molecular breeding of cucurbit crops.

Phenotypic, genetic, variation, and molecular function of CaMYB113 in pepper (Capsicum annuum L.)

Pepper (Capsicum annuum L.) is widely consumed vegetables worldwide, and F1 hybrids are highly sought after in the pepper seed industry. However, studies on gene mutations affecting the color of cotyledon are rare, and the same is true for peppers. In this study, a segregating population was developed by crossing the pepper accession 21C1344 with purple cotyledon and accession 21C912 with green cotyledon. Initially, a target genomic region was identified by screening polymorphic SSR markers distributed across 12 chromosomes. Subsequently, polymorphic markers were developed based on resequencing data from the two parental lines, and genetic linkage analysis was performed. This approach ultimately identified Capana10g001433 (CaMYB113) as the candidate gene responsible for the purple cotyledons. The gene mutation type in 21C912 represents a new mutation type distinct from the reported missense mutation types, and this mutation affects the biosynthesis of anthocyanins. Virus-induced gene silencing (VIGS) of CaMYB113 substantially decreased anthocyanin accumulation in the cotyledons. Subsequent overexpression of CaMYB113 resulted in purple callus and leaves of pepper, and changed the expression levels of downstream genes involved in anthocyanin synthesis. Yeast one-hybrid and dual-luciferase transient expression assays demonstrated the binding of CaMYB113 to anthocyanin biosynthesis-related genes, thereby regulating anthocyanin accumulation in pepper cotyledons.

Silencing of SlMYB78-like Reduces the Tolerance to Drought and Salt Stress via the ABA Pathway in Tomato

The MYB transcription factor family plays a crucial regulatory role in plant growth, development, biological progress, and stress responses. Here, we identified a R2R3-MYB transcription factor gene, SlMYB78-like, from tomato and characterized its function by gene silencing via RNA interference (RNAi). The results exhibited that the silencing of SlMYB78-like reduced the sensitivity of tomato seedlings to exogenous ABA. In addition, when exposed to drought and salt stresses, the RNAi lines grown in soil showed decreased tolerance, with lower ABA accumulation, relative water content, and chlorophyll content while displaying higher relative conductivity and malondialdehyde (MDA) content than the wild type. Moreover, the expression of genes related to chlorophyll biosynthesis, photosynthesis, and ABA biosynthesis/response were down-regulated in SlMYB78-like-silenced lines. Notably, the transcript level of SlCYP707-A2, which encodes a protein involved in ABA degradation, was up-regulated significantly after stresses. The transient expression assay Dual-luciferase (Dual-LUC) and a yeast one-hybrid (Y1H) assay demonstrated that SlMYB78-like bound to the promoter of SlCYP707-A2. Additionally, the physical interaction between SlMYB78-like and SlDREB3, which functioned in ABA signaling transduction, was identified through yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays. Collectively, our study illustrates that SlMYB78-like participates in the abiotic stress response via the ABA pathway.