Genome-Wide Analysis of Soybean LATERAL ORGAN BOUNDARIES Domain-Containing Genes: A Functional Investigation of GmLBD12

Functional and transcriptomic characterization of the receptor-like protein kinase gene GmHSL1b involved in salt stress tolerance in soybean roots

The survival and adaptation of plants to adverse environmental conditions is crucial and is facilitated by receptor-like kinases, which act as cell surface receptors for a variety of signals. In this study, we identified a gene, GmHSL1b, encoding a receptor-like protein kinase that is responsive to abscisic acid (ABA) hormonal signals and is involved in the plant's response to drought and salt stresses. Subcellular localization assays have demonstrated that the GmHSL1b protein is located in the plasma membrane. Overexpression of the GmHSL1b gene in soybean enhanced root growth and development, as well as the plant's tolerance to salt stress, while the gmhsl1b mutant revealed increased sensitivity to salt stress. Comparative transcriptome analysis showed that some genes associated with various biological processes, such as mitogen-activated protein kinase (MAPK) cascade signaling, plant hormone signaling, cell wall remodeling, calcium signaling, and defense response mechanisms are differentially expressed in GmHSL1b overexpressing roots. Our research indicated that GmHSL1b can regulate the expression level of the candidate aquaporin GmPIP2-1, thereby affecting cell water content and the accumulation of reactive oxygen species (ROS) under salt stress. These findings indicate that the GmHSL1b participates in regulating root development and enhancing the tolerance to salt stress, thus offering insights for boosting crop adaptability to environmental stresses.

The members of zinc finger-homeodomain (ZF-HD) transcription factors are associated with abiotic stresses in soybean: insights from genomics and expression analysis

BACKGROUND

Zinc finger homeodomain (ZF-HD) belongs to the plant-specific transcription factor (TF) family and is widely involved in plant growth, development and stress responses. Despite their importance, a comprehensive identification and analysis of ZF-HD genes in the soybean (Glycine max) genome and their possible roles under abiotic stress remain unexplored.

RESULTS

In this study, 51 ZF-HD genes were identified in the soybean genome that were unevenly distributed on 17 chromosomes. All GmZF-HD genes contained a conserved ZF-HD_dimer domain and had diverse physicochemical features. Furthermore, the GmZF-HD gene structures exhibited 3 to 10 conserved motifs, and most of them showed intronless gene structures. Phylogenetic analysis categorized them into eight major groups with the highest closeness to dicots including Brassica rapa and Malus domestica. The cis-element analysis recognized plant growth and development (10%), phytohormones (31%) and stress-responsive (59%) elements. Synteny analysis identified 73 segmental and 1 tandem duplicated genes that underwent purifying selection. The collinearity analysis revealed that GmZF-HD genes showed higher homology with dicot species, indicating common ancestors with close evolutionary relationships. A total of 94 gma-miRNAs from 41 diverse miRNA families were identified, targeting 40 GmZF-HD genes, with GmZF-HD6 being most targeted by 7 miRNAs, and gma-miR4993 emerging as the dominant miRNA family. Different TFs including ERF, LBD, BBR-BPC and MYB, etc., were predicted in all 51 GmZF-HD genes upstream regions and visualized in the network. Expression profiling through RNA-Seq showed diverse expressions of GmZF-HD genes in different tissues including seeds, roots, shoots and leaves under diverse conditions. Further, the qRT-PCR analysis demonstrated that all tested GmZF-HD genes were significantly induced in soybean leaves, mainly the GmZF-HD5/6/13/39 and GmZF-HD45 genes were significantly upregulated (2.5 to 8.8 folds) under the tested stress treatments compared to control, highlighting their potential roles in response to stresses in soybean.

CONCLUSION

Overall, this study reveals comprehensive insights into the ZF-HD genes in soybeans and provides a valuable contribution towards functional studies for soybean improvement under stress conditions.

Genome-Wide Analysis Elucidates the Roles of AhLBD Genes in Different Abiotic Stresses and Growth and Development Stages in the Peanut (Arachis hypogea L.)

The lateral organ boundaries domain (LBD) genes, as the plant-specific transcription factor family, play a crucial role in controlling plant architecture and stress tolerance. However, the functions of AhLBD genes in the peanut plant (Arachis hypogea L.) remain unclear. In this study, 73 AhLBDs were identified in the peanut plant and divided into three groups by phylogenetic tree analysis. Gene structure and conserved protein motif analysis supported the evolutionary conservation of AhLBDs. Tandem and segment duplications contributed to the expansion of AhLBDs. The evolutionary relationship analysis of LBD gene family between A. hypogaea and four other species indicated that the peanut plant had a close relationship with the soybean plant. AhLBDs played a very important role in response to growth and development as well as abiotic stress. Furthermore, gene expression profiling and real-time quantitative qRT-PCR analysis showed that AhLBD16, AhLBD33, AhLBD67, and AhLBD72 were candidate genes for salt stress, while AhLBD24, AhLBD33, AhLBD35, AhLBD52, AhLBD67, and AhLBD71 were candidate genes for drought stress. Our subcellular localization experiment revealed that AhLBD24, AhLBD33, AhLBD67, and AhLBD71 were located in the nucleus. Heterologous overexpression of AhLBD33 and AhLBD67 in Arabidopsis significantly enhanced tolerance to salt stress. Our results provide a theoretical basis and candidate genes for studying the molecular mechanism for abiotic stress in the peanut plant.

Characterization and expression profiles of the ZmLBD gene family in Zea mays

BACKGROUND

The Lateral Organ Boundaries Domain (LBD) gene family is a family of plant-specific transcription factors (TFs) that are widely involved in processes such as lateral organ formation, stress response, and nutrient metabolism. However, the function of LBD genes in maize remains poorly understood.

METHODS AND RESULTS

In this study, a total of 49 ZmLBD genes were identified at the genome-wide level of maize, they were classified into nine branches based on phylogenetic relationships, and all of them were predicted to be nuclear localized. The 49 ZmLBD genes formed eight pairs of segmental duplicates, and members of the same branches' members had similar gene structure and conserved motif composition. The promoters of ZmLBD genes contain multiple types of cis-acting elements. In addition, by constructing the regulatory network of ZmLBD and other genes and miRNAs, 12 and 22 ZmLBDs were found to be involved in the gene regulatory network and miRNA regulatory network, respectively. The expression pattern analysis suggests that ZmLBD genes may be involved in different biological pathways, and drought stress induced the expressions of two inbred lines.

CONCLUSIONS

The findings enhance our comprehension of the potential roles of the ZmLBD gene family in maize growth and development, which is pivotal for genetic enhancement and breeding efforts pertaining to this significant crop.

Genome-Wide Analysis of the Lateral Organ Boundaries Domain (LBD) Gene Family in Sweet Potato (Ipomoea batatas)

The LBD family is a plant-specific transcription factor family that plays an important role in a variety of biological processes. However, the function of IbLBD genes in sweet potato remains unclear. In this study, we identified a total of 53 IbLBD genes in sweet potato. Genetic structure showed that most of the IbLBD genes contained only two exons. Following the phylogenetic investigation, the IbLBD gene family was separated into Class I (45 members) and Class II (8) members. Both classes of proteins contained relatively conservative Motif1 and Motif2 domains. The chromosomal locations, gene duplications, promoters, PPI network, and GO annotation of the sweet potato LBD genes were also investigated. Furthermore, gene expression profiling and real-time quantitative PCR analysis showed that the expression of 12 IbLBD genes altered in six separate tissues and under various abiotic stresses. The IbLBD genes belonging to Class I were mostly expressed in the primary root, the pencil root, and the leaves of sweet potatoes, while the genes belonging to Class II were primarily expressed in the various sweet potato roots. The IbLBD genes belonging to Class I were mostly expressed in the primary root, the pencil root, and the leaves of sweet potatoes, while the genes belonging to Class II were primarily expressed in the fibrous root, pencil root, and tuber root.

Genome-wide identification and analysis of Lateral Organ Boundaries Domain (LBD) transcription factor gene family in melon (Cucumis melo L.)

Background

Lateral Organ Boundaries Domain (LBD) transcription factor (TF) gene family members play very critical roles in several biological processes like plant-spesific development and growth process, tissue regeneration, different biotic and abiotic stress responses in plant tissues and organs. The LBD genes have been analyzed in various species. Melon (Cucumis melo L.), a member of the Cucurbitaceae family, is economically important and contains important molecules for nutrition and human health such as vitamins A and C, β-carotenes, phenolic acids, phenolic acids, minerals and folic acid. However, no studies have been reported so far about LBD genes in melon hence this is the first study for LBD genes in this plant.

Results

In this study, 40 melon CmLBD TF genes were identified, which were separated into seven groups through phylogenetic analysis. Cis-acting elements showed that these genes were associated with plant growth and development, phytohormone and abiotic stress responses. Gene Ontology (GO) analysis revealed that of CmLBD genes especially function in regulation and developmental processes. The in silico and qRT-PCR expression patterns demonstrated that CmLBD01 and CmLBD18 are highly expressed in root and leaf tissues, CmLBD03 and CmLBD14 displayed a high expression in male-female flower and ovary tissues.

Conclusions

These results may provide important contributions for future research on the functional characterization of the melon LBD gene family and the outputs of this study can provide information about the evolution and characteristics of melon LBD gene family for next studies.

Genome-Wide Identification and Expression Analysis of AS2 Genes in Brassica rapa Reveal Their Potential Roles in Abiotic Stress

The ASYMMETRIC LEAVES2/LATERAL ORGAN BOUNDARIES (AS2/LOB) gene family plays a pivotal role in plant growth, induction of phytohormones, and the abiotic stress response. However, the AS2 gene family in Brassica rapa has yet to be investigated. In this study, we identified 62 AS2 genes in the B. rapa genome, which were classified into six subfamilies and distributed across 10 chromosomes. Sequence analysis of BrAS2 promotors showed that there are several typical cis-elements involved in abiotic stress tolerance and stress-related hormone response. Tissue-specific expression analysis showed that BrAS2-47 exhibited ubiquitous expression in all tissues, indicating it may be involved in many biological processes. Gene expression analysis showed that the expressions of BrAS2-47 and BrAS2-10 were significantly downregulated under cold stress, heat stress, drought stress, and salt stress, while BrAS2-58 expression was significantly upregulated under heat stress. RT-qPCR also confirmed that the expression of BrAS2-47 and BrAS2-10 was significantly downregulated under cold stress, drought stress, and salt stress, and in addition BrAS2-56 and BrAS2-4 also changed significantly under the three stresses. In addition, protein-protein interaction (PPI) network analysis revealed that the Arabidopsis thaliana genes AT5G67420 (homologous gene of BrAS2-47 and BrAS2-10) and AT3G49940 (homologous gene of BrAS2-58) can interact with NIN-like protein 7 (NLP7), which has been previously reported to play a role in resistance to adverse environments. In summary, our findings suggest that among the BrAS2 gene family, BrAS2-47 and BrAS2-10 have the most potential for the regulation of abiotic stress tolerance. These results will facilitate future functional investigations of BrAS2 genes in B. rapa.

Genome-Wide Identification of LBD Genes in Foxtail Millet (Setaria italica) and Functional Characterization of SiLBD21

Plant-specific lateral organ boundaries domain (LBD) proteins play important roles in plant growth and development. Foxtail millet (Setaria italica) is one new C₄ model crop. However, the functions of foxtail millet LBD genes are unknown. In this study, a genome-wide identification of foxtail millet LBD genes and a systematical analysis were conducted. A total of 33 SiLBD genes were identified. They are unevenly distributed on nine chromosomes. Among these SiLBD genes, six segmental duplication pairs were detected. The thirty-three encoded SiLBD proteins could be classified into two classes and seven clades. Members in the same clade have similar gene structure and motif composition. Forty-seven kinds of cis-elements were found in the putative promoters, and they are related to development/growth, hormone, and abiotic stress response, respectively. Meanwhile, the expression pattern was investigated. Most SiLBD genes are expressed in different tissues, while several genes are mainly expressed in one or two kinds of tissues. In addition, most SiLBD genes respond to different abiotic stresses. Furthermore, the function of SiLBD21, which is mainly expressed in roots, was characterized by ectopic expression in Arabidopsis and rice. Compared to controls, transgenic plants generated shorter primary roots and more lateral roots, indicating the function of SiLBD21 in root development. Overall, our study laid the foundation for further functional elucidation of SiLBD genes.

Genome-wide characterization of LBD transcription factors in switchgrass (Panicum virgatum L.) and the involvement of PvLBD12 in salt tolerance

PvLBD12 enhanced the salt tolerance by increasing proline accumulation, improving K⁺ accumulation, and decreasing reactive oxygen species level in switchgrass. Abiotic stresses are the serious factors which limit plant development and productivity and restrict the agricultural economy. It is important, therefore, to understand the mechanism of abiotic tolerance in plants. Lateral organ boundaries domain (LBD) proteins as plant-specific transcription factors play important function in plant lateral organ development, plant regeneration, and abiotic stress. In our study, we identify 69 LBD members from switchgrass genome-wide sequences and classify them based on their homology with LBD proteins in Arabidopsis. RT-qPCR showed that PvLBD genes had different expression patterns under abiotic stress conditions, indicating that they play important roles in various stress. PvLBD12 was selected as a candidate gene for further functional analysis because it had the highest expression level under salt stress. Overexpression of PvLBD12 enhanced salt tolerance by altering a wide range of physiological responses (like increased proline accumulation, reduced malondialdehyde production, improved K⁺ accumulation, and reduced Na⁺ absorption) in switchgrass. Some stress response genes such as proline biosynthesis gene PvP5CS1, vacuolar Na⁺(K⁺)/H⁺ antiporter gene PvNHX1, two key ROS-scavenging enzyme genes PvCAT and PvSOD were all upregulated in PvLBD12 overexpression lines. Taken together, PvLBD12 plays a pivotal role in response to salt stress by increasing proline accumulation, improving K⁺ accumulation, reducing Na⁺ absorption, and decreasing reactive oxygen species level. It will be better to understand the potential biological functions of LBD genes in other plants.

Genome-Wide Analysis of the LATERAL ORGAN BOUNDARIES Domain (LBD) Members in Alfalfa and the Involvement of MsLBD48 in Nitrogen Assimilation

The LATERAL ORGAN BOUNDARIES DOMAIN (LBD) proteins, a transcription factor family specific to the land plants, have been implicated in multiple biological processes including organ development, pathogen response and the uptake of inorganic nitrogen. The study focused on LBDs in legume forage Alfalfa. The genome-wide analysis revealed that in Alfalfa 178 loci across 31 allelic chromosomes encoded 48 unique LBDs (MsLBDs), and the genome of its diploid progenitor M. sativa spp. Caerulea encoded 46 LBDs. Synteny analysis indicated that the expansion of AlfalfaLBDs was attributed to the whole genome duplication event. The MsLBDs were divided into two major phylogenetic classes, and the LOB domain of the Class I members was highly conserved relative to that of the Class II. The transcriptomic data demonstrated that 87.5% of MsLBDs were expressed in at least one of the six test tissues, and Class II members were preferentially expressed in nodules. Moreover, the expression of Class II LBDs in roots was upregulated by the treatment of inorganic nitrogen such as KNO3 and NH4Cl (0.3 mM). The overexpression of MsLBD48, a Class II member, in Arabidopsis resulted in growth retardance with significantly declined biomass compared with the non-transgenic plants, and the transcription level of the genes involved in nitrogen uptake or assimilation, including NRT1.1, NRT2.1, NIA1 and NIA2 was repressed. Therefore, the LBDs in Alfalfa are highly conserved with their orthologs in embryophytes. Our observations that ectopic expression of MsLBD48 inhibited Arabidopsis growth by repressing nitrogen adaption suggest the negative role of the transcription factor in plant uptake of inorganic nitrogen. The findings imply the potential application of MsLBD48 in Alfalfa yield improvement via gene editing.

The central role of GmGLP20.4 in root architecture modifications of soybean under low-nitrogen stress

KEY MESSAGE

The GmGLP20.4 candidate gene plays an important role to improve soybean root architecture under low-nitrogen stress. The results lay the foundation for breeding low-nitrogen-tolerant soybean. Roots are fundamentally important for plant growth and development, facilitating water and nutrient uptake. Various abiotic and biotic factors significantly affect the root system architecture, especially low nitrogen (LN), but the molecular mechanism remains unclear. In this study, we identified GmGLP20.4, a germin-like protein (ubiquitous plant glycoproteins belonging to the Cupin superfamily) crucial for lateral root development and highly induced by LN stress in lateral roots of soybean. GmGLP20.4 overexpression increased root biomass through development of an improved root system in soybean under LN, whereas a significant decrease in root biomass was observed in the gmglp20.4 knockout mutant. Overexpression of GmGLP20.4 improved plant growth and root architecture in transgenic tobacco (Nicotiana tabacum) under LN. Natural variation of the GT-1 cis-element in the promoter (T to A) of GmGLP20.4 was strongly associated with its expression level under LN, and significantly increased LN-sensitive variation (type A) was observed in wild soybean compared to that in elite cultivars. Thus, type A variation in the promoter of GmGLP20.4 may have been a site of artificial selection during domestication. The GmGT1-16g gene was highly expressed under LN and showed an expression pattern opposite to that of GmGLP20.4. A luciferase complementation imaging assay revealed that the GmGLP20.4 promoter specifically binds to GmGT1-16g. In conclusion, GmGLP20.4 is involved in soybean root development and the natural variation of its promoter will be useful in modern intercropping systems or to improve nitrogen-use efficiency.

Genome-Wide Identification of the Ginkgo (Ginkgo biloba L.) LBD Transcription Factor Gene and Characterization of Its Expression

Lateral organ boundaries domain (LBD) proteins are plant-specific transcription factors involved in various transcriptional regulation processes. We identified a total of 37 GbLBD genes in ginkgo, and based on gene structure and phylogenetic analysis, the GbLBD gene family was classified into class I (33, with the largest number of Id genes (16)) and class II (4). The ginkgo LBD gene was also analyzed regarding its chromosomal distributions, gene duplications, promoters, and introns/exons. In addition, gene expression profiling and real-time quantitative PCR analysis showed that the expression of 14 GbLBD genes differed in six different tissues and three developmental stages. The GbLBD gene of class II were highly expressed relative to the class I gene in all tissues and developmental stages, while class Id gene were generally at low levels or were not expressed, especially in seed developmental stages. The expression pattern analysis of cold/drought treatment and IAA/ABA hormone treatment showed that abiotic stress treatment could significantly induce the expression of GbLBD gene, of which class II genes played a key role in stress treatment. Our study provides a solid foundation for further evolutionary and functional analysis of the ginkgo LBD gene family.

Genome-Wide Analysis of Soybean Lateral Organ Boundaries Domain Gene Family Reveals the Role in Phytophthora Root and Stem Rot

The plant-specific lateral organ boundaries (LOB) domain (LBD) proteins, a family of transcription factors, play important roles in plant growth and development, as well as in responses to various stresses. However, little is known about the functions of LBD genes in soybean (Glycine max). In this study, we investigated the evolution and classification of the LBD family in soybean by a phylogenetic tree of the LBD gene family from 16 species. Phylogenetic analysis categorized these proteins into two classes (Class I and Class II) with seven subgroups. Moreover, we found that all the 18 LBD ancestors in angiosperm were kept in soybean, common bean genomes, and genome-wide duplication, suggesting the main force for the expansion of LBD from common bean to soybean. Analysis of gene expression profiling data indicated that 16 GmLBD genes were significantly induced at different time points after inoculation of soybean plants (cv. Huachun 6) with Phytophthora sojae (P. sojae). We further assessed the role of four highly upregulated genes, GmLBD9, GmLBD16, GmLBD23, and GmLBD88, in plant defense in soybean hairy roots using the transient overexpression and knockdown assays. The results showed that GmLBD9 and GmLBD23 negatively regulate plant immunity against P. sojae, whereas GmLBD16 and GmLBD88 positively manipulate plant immunity against P. sojae. Collectively, our findings expand our knowledge of the origin and evolution of the GmLBD gene family in soybean and promote the potential application of these genes in soybean genetic improvement.

Genome-wide promoter analysis, homology modeling and protein interaction network of Dehydration Responsive Element Binding (DREB) gene family in Solanum tuberosum

Dehydration Responsive Element Binding (DREB) regulates the expression of numerous stress-responsive genes, and hence plays a pivotal role in abiotic stress responses and tolerance in plants. The study aimed to develop a complete overview of the cis-acting regulatory elements (CAREs) present in S. tuberosum DREB gene promoters. A total of one hundred and four (104) cis-regulatory elements (CREs) were identified from 2.5kbp upstream of the start codon (ATG). The in-silico promoter analysis revealed variable sets of cis-elements and functional diversity with the predominance of light-responsive (30%), development-related (20%), abiotic stress-responsive (14%), and hormone-responsive (12%) elements in StDREBs. Among them, two light-responsive elements (Box-4 and G-box) were predicted in 64 and 61 StDREB genes, respectively. Two development-related motifs (AAGAA-motif and as-1) were abundant in StDREB gene promoters. Most of the DREB genes contained one or more Myeloblastosis (MYB) and Myelocytometosis (MYC) elements associated with abiotic stress responses. Hormone-responsive element i.e. ABRE was found in 59 out of 66 StDREB genes, which implied their role in dehydration and salinity stress. Moreover, six proteins were chosen corresponding to A1-A6 StDREB subgroups for secondary structure analysis and three-dimensional protein modeling followed by model validation through PROCHECK server by Ramachandran Plot. The predicted models demonstrated >90% of the residues in the favorable region, which further ensured their reliability. The present study also anticipated pocket binding sites and disordered regions (DRs) to gain insights into the structural flexibility and functional annotation of StDREB proteins. The protein association network determined the interaction of six selected StDREB proteins with potato proteins encoded by other gene families such as MYB and NAC, suggesting their similar functional roles in biological and molecular pathways. Overall, our results provide fundamental information for future functional analysis to understand the precise molecular mechanisms of the DREB gene family in S. tuberosum.

Genome-wide identification and characterization of the Lateral Organ Boundaries Domain (LBD) gene family in polyploid wheat and related species

BACKGROUND

Wheat (Triticum aestivum) originated from three different diploid ancestral grass species and experienced two rounds of polyploidization. Exploring how certain wheat gene subfamilies have expanded during the evolutionary process is of great importance. The Lateral Organ Boundaries Domain (LBD) gene family encodes plant-specific transcription factors that share a highly conserved LOB domain and are prime candidates for this, as they are involved in plant growth, development, secondary metabolism and stress in various species.

METHODS

Using a genome-wide analysis of high-quality polyploid wheat and related species genome sequences, a total of 228 LBD members from five Triticeae species were identified, and phylogenetic relationship analysis of LBD members classified them into two main classes (classes I and II) and seven subgroups (classes I a-e, II a and II b).

RESULTS

The gene structure and motif composition analyses revealed that genes that had a closer phylogenetic relationship in the same subgroup also had a similar gene structure. Macrocollinearity and microcollinearity analyses of Triticeae species suggested that some LBD genes from wheat produced gene pairs across subgenomes of chromosomes 4A and 5A and that the complex evolutionary history of TaLBD4B-9 homologs was a combined result of chromosome translocation, polyploidization, gene loss and duplication events. Public RNA-seq data were used to analyze the expression patterns of wheat LBD genes in various tissues, different developmental stages and following abiotic and biotic stresses. Furthermore, qRT-PCR results suggested that some TaLBDs in class II responded to powdery mildew, regulated reproductive growth and were involved in embryo sac development in common wheat.

RNAi of a Putative Grapevine Susceptibility Gene as a Possible Downy Mildew Control Strategy

Downy mildew, caused by the oomycete Plasmopara viticola, is one of the diseases causing the most severe economic losses to grapevine (Vitis vinifera) production. To date, the application of fungicides is the most efficient method to control the pathogen and the implementation of novel and sustainable disease control methods is a major challenge. RNA interference (RNAi) represents a novel biotechnological tool with a great potential for controlling fungal pathogens. Recently, a candidate susceptibility gene (VviLBDIf7) to downy mildew has been identified in V. vinifera. In this work, the efficacy of RNAi triggered by exogenous double-stranded RNA (dsRNA) in controlling P. viticola infections has been assessed in a highly susceptible grapevine cultivar (Pinot noir) by knocking down VviLBDIf7 gene. The effects of dsRNA treatment on this target gene were assessed by evaluating gene expression, disease severity, and development of vegetative and reproductive structures of P. viticola in the leaf tissues. Furthermore, the effects of dsRNA treatment on off-target (EF1α, GAPDH, PEPC, and PEPCK) and jasmonic acid metabolism (COI1) genes have been evaluated. Exogenous application of dsRNA led to significant reductions both in VviLBDIf7 gene expression, 5 days after the treatment, and in the disease severity when artificial inoculation was carried out 7 days after dsRNA treatments. The pathogen showed clear alterations to both vegetative (hyphae and haustoria) and reproductive structures (sporangiophores) that resulted in stunted growth and reduced sporulation. Treatment with dsRNA showed signatures of systemic activity and no deleterious off-target effects. These results demonstrated the potential of RNAi for silencing susceptibility factors in grapevine as a sustainable strategy for pathogen control, underlying the possibility to adopt this promising biotechnological tool in disease management strategies.

Genome-Wide Identification, Evolution, and Expression Analysis of LBD Transcription Factor Family in Bread Wheat (Triticum aestivum L.)

The lateral organ boundaries domain (LBD) genes, as the plant-specific transcription factor family, play a crucial role in controlling plant architecture and stress tolerance. Although it has been thoroughly characterized in many species, the LBD family was not well studied in wheat. Here, the wheat LBD family was systematically investigated through an in silico genome-wide search method. A total of 90 wheat LBD genes (TaLBDs) were identified, which were classified into class I containing seven subfamilies, and class II containing two subfamilies. Exon-intron structure, conserved protein motif, and cis-regulatory elements analysis showed that the members in the same subfamily shared similar gene structure organizations, supporting the classification. Furthermore, the expression patterns of these TaLBDs in different types of tissues and under diverse stresses were identified through public RNA-seq data analysis, and the regulation networks of TaLBDs involved were predicted. Finally, the expression levels of 12 TaLBDs were validated by quantitative PCR (qPCR) analysis and the homoeologous genes showed differential expression. Additionally, the genetic diversity of TaLBDs in the landrace population showed slightly higher than that of the genetically improved germplasm population while obvious asymmetry at the subgenome level. This study not only provided the potential targets for further functional analysis but also contributed to better understand the roles of LBD genes in regulating development and stress tolerance in wheat and beyond.

CRISPR/Cas9 targeted mutagenesis of SlLBD40, a lateral organ boundaries domain transcription factor, enhances drought tolerance in tomato

The LATERAL ORGAN BOUNDARIES DOMAIN (LBD)-containing genes are plant-specific genes that play important roles in lateral organ development. In this study, we identified LBD40 (Solyc02g085910), which belongs to subfamily II of the LBD family of genes in tomato. LBD40 was highly expressed in roots and fruit. LBD40 expression was significantly induced by PEG and salt. Moreover, SlLBD40 expression was induced by methyl jasmonate treatment, while SlLBD40 expression could not be induced in the jasmonic acid-insensitive1 (jai1) mutant or MYC2-silenced plants, in which jasmonic acid (JA) signaling was disrupted. These findings demonstrate that SlLBD40 expression was dependent on JA signaling and that it might be downstream of SlMYC2, which is the master transcription factor in the JA signal transduction pathway. Overexpressing and CRISPR/Cas9 mediated knockout transgenic tomato plants were generated to explore SlLBD40 function. The drought tolerance test showed that two SlLBD40 knockout lines wilted slightly, while SlLBD40 overexpressing plants suffered severe wilting. The statistical water loss rate and midday leaf water potential also confirmed that knockout of SlLBD40 improved the water-holding ability of tomato under drought conditions. Taken together, our study demonstrates that SlLBD40, involved in JA signaling, was a negative regulator of drought tolerance and that knockout of SlLBD40 enhanced drought tolerance in tomato. This study also provides a novel function of SlLBD40, which belongs to subfamily II of LBD genes.

Comprehensive characterization and gene expression patterns of LBD gene family in Gossypium

A comprehensive account of the LBD gene family of Gossypium was provided in this work. Expression analysis and functional characterization revealed that LBD genes might play different roles in G. hirsutum and G. barbadense. The Lateral Organ Boundaries Domain (LBD) proteins comprise a plant-specific transcription factor family, which plays crucial roles in physiological processes of plant growth, development, and stress tolerance. In the present work, a systematical analysis of LBD gene family from two allotetraploid cotton species, G. hirsutum and G. barbadense, together with their genomic donor species, G. arboreum and G. raimondii, was conducted. There were 131, 128, 62, and 68 LBDs identified in G. hirsutum, G. barbadense, G. arboreum and G. raimondii, respectively. The LBD proteins could be classified into two main classes, class I and class II, based on the structure of their lateral organ boundaries domain and traits of phylogenetic tree, and class I was further divided into five subgroups. The gene structure and motif composition analyses conducted in both G. hirsutum and G. barbadense revealed that LBD genes kept relatively conserved within the subfamilies. Synteny analysis suggested that segmental duplication acted as an important mechanism in expansion of the cotton LBD gene family. Cis-element analysis predicated the possible functions of LBD genes. Public RNA-seq data were investigated to analyze the expression patterns of cotton LBD genes in various tissues as well as gene expression under abiotic stress treatments. Furthermore, RT-qPCR results found that GhLBDs had various expression regulation under MeJA treatments. Expression analysis indicated the differential functions of cotton LBD genes in response to abiotic stress and hormones.

Genome-Wide Analysis of the Lateral Organ Boundaries Domain Gene Family in Brassica Napus

The plant specific LATERAL ORGAN BOUNDARIES (LOB)-domain (LBD) proteins belong to a family of transcription factors that play important roles in plant growth and development, as well as in responses to various stresses. However, a comprehensive study of LBDs in Brassica napus has not yet been reported. In the present study, 126 BnLBD genes were identified in B. napus genome using bioinformatics analyses. The 126 BnLBDs were phylogenetically classified into two groups and nine subgroups. Evolutionary analysis indicated that whole genome duplication (WGD) and segmental duplication played important roles in the expansion of the BnLBD gene family. On the basis of the RNA-seq analyses, we identified BnLBD genes with tissue or developmental specific expression patterns. Through cis-acting element analysis and hormone treatment, we identified 19 BnLBD genes with putative functions in plant response to abscisic acid (ABA) treatment. This study provides a comprehensive understanding on the origin and evolutionary history of LBDs in B. napus, and will be helpful in further functional characterisation of BnLBDs.

Genome-Wide DNA Methylation Analysis of Soybean Curled-Cotyledons Mutant and Functional Evaluation of a Homeodomain-Leucine Zipper (HD-Zip) I Gene GmHDZ20

DNA methylation is a major, conserved epigenetic modification that influences many biological processes. Cotyledons are specialized tissues that provide nutrition for seedlings at the early developmental stage. To investigate the patterns of genomic DNA methylation of germinated cotyledons in soybean (Glycine max) and its effect on cotyledon development, we performed a genome-wide comparative analysis of DNA methylation between the soybean curled-cotyledons (cco) mutant, which has abnormal cotyledons, and its corresponding wild type (WT) by whole-genome bisulfite sequencing. The cco mutant was methylated at more sites but at a slightly lower level overall than the WT on the whole-genome level. A total of 46 CG-, 92 CHG-, and 9723 CHH- (H = A, C, or T) differentially methylated genes (DMGs) were identified in cotyledons. Notably, hypomethylated CHH-DMGs were enriched in the gene ontology term "sequence-specific DNA binding transcription factor activity." We selected a DMG encoding a homeodomain-leucine zipper (HD-Zip) I subgroup transcription factor (GmHDZ20) for further functional characterization. GmHDZ20 localized to the nucleus and was highly expressed in leaf and cotyledon tissues. Constitutive expression of GmHDZ20 in Arabidopsis thaliana led to serrated rosette leaves, shorter siliques, and reduced seed number per silique. A yeast two-hybrid assay revealed that GmHDZ20 physically interacted with three proteins associated with multiple aspects of plant growth. Collectively, our results provide a comprehensive study of soybean DNA methylation in normal and aberrant cotyledons, which will be useful for the identification of specific DMGs that participate in cotyledon development, and also provide a foundation for future in-depth functional study of GmHDZ20 in soybean.

Structural and functional insights into the LBD family involved in abiotic stress and flavonoid synthases in Camellia sinensis

Lateral organ boundaries domain (LBD) proteins are plant-specific transcription factors that play a crucial role in growth and development, as well as metabolic processes. However, knowledge of the function of LBD proteins in Camellia sinensis is limited, and no systematic investigations of the LBD family have been reported. In this study, we identified 54 LBD genes in Camellia sinensis. The expression patterns of CsLBDs in different tissues and their transcription responses to exogenous hormones and abiotic stress were determined by RNA-seq, which showed that CsLBDs may have diverse functions. Analysis of the structural gene promoters revealed that the promoters of CsC4H, CsDFR and CsUGT84A, the structural genes involved in flavonoid biosynthesis, contained LBD recognition binding sites. The integrative analysis of CsLBD expression levels and metabolite accumulation also suggested that CsLBDs are involved in the regulation of flavonoid synthesis. Among them, CsLOB_3, CsLBD36_2 and CsLBD41_2, localized in the nucleus, were selected for functional characterization. Yeast two-hybrid assays revealed that CsLBD36_2 and CsLBD41_2 have self-activation activities, and CsLOB_3 and CsLBD36_2 can directly bind to the cis-element and significantly increase the activity of the CsC4H, CsDFR and CsUGT84A promoter. Our results present a comprehensive characterization of the 54 CsLBDs in Camellia sinensis and provide new insight into the important role that CsLBDs play in abiotic and flavonoid biosynthesis.

Overexpression of a soybean YABBY gene, GmFILa, causes leaf curling in Arabidopsis thaliana

BACKGROUND

YABBY genes play important roles in the growth and polar establishment of lateral organs such as leaves and floral organs in angiosperms. However, the functions of YABBY homologous genes are largely unknown in soybean.

RESULTS

In this study, we identified GmFILa encoding a YABBY transcription factor belonging to FIL subfamily. In situ mRNA hybridization analysis indicated that GmFILa had specific expression patterns in leaf as well as in flower bud primordia. Ectopic expression of GmFILa in Arabidopsis thaliana altered the partial abaxialization of the adaxial epidermises of leaves. Besides, GmFILa transgenic plants also exhibited longer flowering period and inhibition of shoot apical meristem (SAM) development compared to the wild type plants. Digital expression data and quantitative real-time polymerase chain reaction (qRT-PCR) analysis demonstrated that the expression of GmFILa was induced by biotic and abiotic stresses and hormone treatments. Transcriptome analysis suggested that overexpressing GmFILa yielded 82 significant differentially expressed genes (DEGs) in Arabidopsis leaves, which can be classified into transcription factors, transporters, and genes involved in growth and development, metabolism, signal transduction, redox reaction and stress response.

CONCLUSIONS

These results not only demonstrate the roles of GmFILa involved in leaf adaxial-abaxial polarity in Arabidopsis, but also help to reveal the molecular regulatory mechanism of GmFILa based on the transcriptomic data.

RNA-Seq analysis reveals transcript diversity and active genes after common cutworm (Spodoptera litura Fabricius) attack in resistant and susceptible wild soybean lines

BACKGROUND

Common cutworm (CCW) is highly responsible for destabilizing soybean productivity. Wild soybean is a resource used by breeders to discover elite defensive genes.

RESULTS

The transcriptomes of two wild accessions (W11 and W99) with different resistance to CCW were analyzed at early- and late-induction time points. After induction, the susceptible accession W11 differentially expressed 1268 and 508 genes at the early and late time points, respectively. Compared with W11, the resistant accession W99 differentially expressed 1270 genes at the early time point and many more genes (2308) at the late time point. In total, 3836 non-redundant genes were identified in both lines. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed that the differentially expressed genes (DEGs) in W99 at the late time point were mostly associated with specific processes and pathways. Among the non-redundant genes, 146 genes were commonly up-regulated in the treatment condition compared with the control condition at the early- and late-induction time points in both accessions used in this experiment. Approximately 40% of the common DEGs were related to secondary metabolism, disease resistance, and signal transduction based on their putative function. Excluding the common DEGs, W99 expressed more unique DEGs than W11. Further analysis of the 3836 DEGs revealed that the induction of CCW not only up-regulated defense-related genes, including 37 jasmonic acid (JA)-related genes, 171 plant-pathogen-related genes, and 17 genes encoding protease inhibitors, but also down-regulated growth-related genes, including 35 photosynthesis-related genes, 48 nutrition metabolism genes, and 28 auxin metabolism genes. Therefore, representative defense-related and growth-related genes were chosen for binding site prediction via co-expression of transcription factors (TFs) and spatial expression pattern analyses. In total, 53 binding sites of 28 TFs were identified based on 3 defense-related genes and 3 growth-related genes. Phosphate transporter PT1, which is a representative growth-related gene, was transformed into soybean, and the transgenic soybean plants were susceptible to CCW.

CONCLUSIONS

In summary, we described transcriptome reprograming after herbivore induction in wild soybean, identified the susceptibility of growth-related genes, and provided new resources for the breeding of herbivore-resistant cultivated soybeans.