HSG1, a grape Bcl-2-associated athanogene, promotes floral transition by activating CONSTANS expression in transgenic Arabidopsis plant

Identification and functional analysis of BAG gene family contributing to verticillium wilt resistance in upland cotton

Cotton fiber is a primary textile material and a significant economic resource globally. Verticillium dahliae, a destructive soil-borne fungal pathogen, severely impacts cotton yields. The Bcl-2-associated athanogene (BAG) protein family, functioning as molecular chaperone co-chaperones, plays a crucial role in plant stress responses. In this study, 24, 12, and 11 BAG genes were identified in upland cotton (Gossypium hirsutum), Asiatic cotton (G. arboreum), and Levant cotton (G. raimondii), respectively. The BAG gene family demonstrates relative conservation throughout cotton evolution. Conserved domain analysis revealed that BAG proteins from these species universally contain the conserved BAG domain, with some members also possessing the UBL domain and CaM-binding motifs. Virus-induced gene silencing (VIGS) was utilized to investigate gene function in upland cotton. Compared to the negative control, following V. dahliae infection, the silencing of GhBAG7.1 and GhBAG6.2 makes the plants more susceptible to infection, showing symptoms earlier. Quantitative Real-Time Polymerase Chain Reaction (RT-qPCR) analysis indicated that V. dahliae infection upregulated the expression of GhBAG7.1, GhBAG6.2, and GhBAG4.1 in upland cotton, while GhBAG4.4 expression was downregulated. Furthermore, following the silencing of the GhBAG6.2 gene, V. dahliae infection led to an initial upregulation of disease resistance-related genes (ERF1, PR5, PDF1.2, NPR1, PR1, OPR3), which was followed by a subsequent decrease in their expression. Transcriptomic analysis revealed a transient upregulation of defense-related pathways, including phenylpropanoid biosynthesis, MAPK signaling pathway, and plant-pathogen interactions, at 48- and 96-hours post-inoculation with V. dahliae. The findings provide a foundation for future research on stress-tolerant genes in cotton and offer new genetic resources for breeding disease-resistant cotton varieties.

Identification and evaluation of BAG (B-cell lymphoma-2 associated athanogene) family gene expression in pigeonpea (Cajanus cajan) under terminal heat stress

Introduction

Heat stress poses a significant environmental challenge, impacting plant growth, diminishing crop production, and reducing overall productivity. Plants employ various mechanisms to confront heat stress, and their ability to survive hinges on their capacity to perceive and activate appropriate physiological and biochemical responses. One such mechanism involves regulating multiple genes and coordinating their expression through different signaling pathways. The BAG (B-cell lymphoma-2 associated athanogene) gene family plays a multifunctional role by interacting with heat shock proteins, serving as co-chaperones, or regulating chaperones during the response to heat stress and development. While numerous studies have explored BAG proteins in model plants, there still remains a knowledge gap concerning crop plants.

Methods

Our study successfully identified nine BAG genes in pigeonpea through genome-wide scanning. A comprehensive in silico analysis was conducted to ascertain their chromosomal location, sub-cellular localization, and the types of regulatory elements present in the putative promoter region. Additionally, an expression analysis was performed on contrasting genotypes exhibiting varying heat stress responses.

Results

The results revealed eight CcBAG genes with higher expression levels in the tolerant genotype, whereas BAG6 (Cc_02358) exhibited lower expression. Upstream sequence analysis identified BAG members potentially involved in multiple stresses.

Discussion

The functional characterization of these BAG genes is essential to unravel their roles in signaling pathways, facilitating the identification of candidate genes for precise breeding interventions to produce heat-resilient pigeonpea.

Involvement of HSP70 in BAG9-mediated thermotolerance in Solanum lycopersicum

Because of a high sensitivity to high temperature, both the yield and quality of tomato (Solanum lycopersicum L.) are severely restricted by heat stress. The Bcl-2-associated athanogene (BAG) proteins, a family of multi-functional co-chaperones, are involved in plant growth, development, and stress tolerance. We have previously demonstrated that BAG9 positively regulates thermotolerance in tomato. However, the BAG9-mediated mechanism of thermotolerance in tomato has remained elusive. In the present study, we report that BAG9 interacts with heat shock protein 70 (HSP70) in vitro and in vivo. Silencing HSP70 decreased thermotolerance of tomato plants, as reflected by the phenotype, relative electrolyte leakage and malondialdehyde. Furthermore, the photosystem activities, activities of antioxidant enzymes and expression of key genes encoding antioxidant enzymes were reduced in HSP70-silenced plants under heat stress. Additionally, silencing HSP70 decreased thermotolerance of overexpressing BAG9 plants, which was related to decreased photosynthetic rate, increased damage to photosystem I and photosystem II, decreased activity of antioxidant enzymes, and decreased expression of key genes encoding antioxidant enzymes. Taken together, the present study identified that HSP70 is involved in BAG9-mediated thermotolerance by protecting the photosystem stability and improving the efficiency of the antioxidant system in tomato. This knowledge can be helpful to breed improved crop cultivars that are better equipped with thermotolerance.

Functional insights of plant bcl-2-associated ahanogene (BAG) proteins: Multi-taskers in diverse cellular signal transduction pathways

Bcl-2-associated athanogene (BAG) gene family is a highly conserved molecular chaperone cofactor in evolution from yeast to humans and plants playing important roles in a variety of signal pathways. Plant BAG proteins have special structures, especially those containing CaM-binding IQ motifs which are unique to plants. While early studies focused more on the structure and physiological function of plant BAGs, recent studies have revealed many novel functional mechanisms involved in multiple cellular processes. How to achieve signal specificity has become an interesting topic of plant BAG research. In this review, we have provided a historic view of plant BAG research and summarized recent advances in the establishment of BAG as essential components in normal plant growth, environmental stress response, and plant immunity. Based on the relationship between BAG proteins and their newly interacting proteins, this review highlights the functional mechanisms of various cellular signals mediated by plant BAGs. Future work needs to focus on the post-translational modification of BAG proteins, and on understanding how specificity is achieved among BAG signaling pathways.

BAG9 Confers Thermotolerance by Regulating Cellular Redox Homeostasis and the Stability of Heat Shock Proteins in Solanum lycopersicum

The Bcl-2-associated athanogene (BAG) family, a group of co-chaperones that share conservative domains in flora and fauna, is involved in plant growth, development, and stress tolerance. However, the function of tomato BAG genes on thermotolerance remains largely unknown. Herein, we found that the expression of BAG9 was induced during heat stress in tomato plants. Knockout of the BAG9 gene by CRISPR/Cas9 reduced, while its overexpression increased thermotolerance in tomato plants as reflected by the phenotype, photosynthesis rate, and membrane peroxidation. Heat-induced reactive oxygen species and oxidative/oxidized proteins were further increased in bag9 mutants and were normalized in BAG9 overexpressing plants. Furthermore, the activities of antioxidant enzymes, ascorbic acid (AsA)/dehydroascorbic acid (DHA), and reduced glutathione (GSH)/oxidized glutathione (GSSG) were reduced in bag9 mutants and were increased in BAG9 overexpressing plants under heat stress. Additionally, BAG9 interacted with Hsp20 proteins in vitro and in vivo. Accumulation of Hsp proteins induced by heat showed a reduction in bag9 mutants; meanwhile, it was increased in BAG9 overexpressing plants. Thus, BAG9 played a crucial role in response to heat stress by regulating cellular redox homeostasis and the stability of heat shock proteins.

Genome-Wide Identification of the Bcl-2 Associated Athanogene (BAG) Gene Family in Solanum lycopersicum and the Functional Role of SlBAG9 in Response to Osmotic Stress

The Bcl-2-associated athanogene (BAG) proteins are a family of multi-functional group of co-chaperones regulators, modulating diverse processes from plant growth and development to stress response. Here, 10 members of SlBAG gene family were identified based on the available tomato (Solanum lycopersicum) genomic information and named as SlBAG1-10 according to their chromosomal location. All SlBAG proteins harbor a characteristic BAG domain, categorized into two groups, and SlBAG4, SlBAG7, and SlBAG9 of group I contain a plant-specific isoleucine glutamine (IQ) calmodulin-binding motif located in the N terminus. The quantitative real-time PCR expression analysis revealed that these SlBAG genes had organ-specific expression patterns and most SlBAG genes were differentially expressed in multiple abiotic stresses including drought, salt, high temperature, cold, and cadmium stress as well as abscisic acid and H2O2. In addition, heterologous overexpression of SlBAG9 increased the sensitivity of Arabidopsis to drought, salt, and ABA during seed germination and seedling growth. The decreased tolerance may be due to the downregulation of stress-related genes expression and severe oxidative stress. The expression levels of some stress and ABA-related genes, such as ABI3, RD29A, DREB2A, and P5CS1, were significantly inhibited by SlBAG9 overexpression under osmotic stress. Meanwhile, the overexpression of SlBAG9 inhibited the expression of FSD1 and CAT1 under stress conditions and the decreased levels of superoxide dismutase and catalase enzyme activities were detected accompanying the trends in the expression of both genes, which resulted in H2O2 accumulation and lipid peroxidation. Taken together, these findings lay a foundation for the future study of the biological function of SlBAG genes in tomato.

Genome-wide in silico characterization and stress induced expression analysis of BcL-2 associated athanogene (BAG) family in Musa spp

Programmed cell death (PCD) is a genetically controlled process for the selective removal of damaged cells. Though understanding about plant PCD has improved over years, the mechanisms are yet to be fully deciphered. Among the several molecular players of PCD in plants, B cell lymphoma 2 (Bcl-2)-associated athanogene (BAG) family of co-chaperones are evolutionary conserved and regulate cell death, growth and development. In this study, we performed a genome-wide in silico analysis of the MusaBAG gene family in a globally important fruit crop banana. Thirteen MusaBAG genes were identified, out of which MusaBAG1, 7 and 8 genes were found to have multiple copies. MusaBAG genes were distributed on seven out of 11 chromosomes in banana. Except for one paralog of MusaBAG8 all the other 12 proteins have characteristic BAG domain. MusaBAG1, 2 and 4 have an additional ubiquitin-like domain whereas MusaBAG5-8 have a calmodulin binding motif. Most of the MusaBAG proteins were predicted to be localized in the nucleus and mitochondria or chloroplast. The in silico cis-regulatory element analysis suggested regulation associated with photoperiodic control, abiotic and biotic stress. The phylogenetic analysis revealed 2 major clusters. Digital gene expression analysis and quantitative real-time RT-PCR depicted the differential expression pattern of MusaBAG genes under abiotic and biotic stress conditions. Further studies are warranted to uncover the role of each of these proteins in growth, PCD and stress responses so as to explore them as candidate genes for engineering transgenic banana plants with improved agronomic traits.

Overexpression of a Bcl-2-associated athanogene SlBAG9 negatively regulates high-temperature response in tomato

The Bcl-2-associated athanogene (BAG) gene is a multi-functional family of co-chaperones regulator, modulating plant stress response. Our previous study revealed that the SlBAG9 of tomato (Solanum lycopersicum) had the higher expression level induced by high-temperature (HT) at the transcriptional and protein levels, but its biological function was still unclear. Here, we conducted an in-depth analysis of SlBAG9. SlBAG9 protein was not located in the mitochondria but in the cytoplasm and nucleus. Many cis-acting elements involved in plant stress and hormone responses were located in the promoter regions of SlBAG9 including heat-shock element (HSE1). The β-glucuronidase (GUS) histochemical analysis showed that SlBAG9 promoter could drive GUS gene expression in transiently transformed Nicotiana tabacum leaves under non-inducing condition and HSE1 is critical for HT-induced GUS activity under HT. The transcription of SlBAG9 was expressed in different organs and was regulated by HT, cold, drought, and salt stresses as well as exogenous abscisic acid (ABA) and H₂O₂. To further elucidate SlBAG9 function in response to HT, the transgenic tomato plants overexpressing SlBAG9 were developed. Compared to the wild-type plants, SlBAG9-overexpressing plants exhibited more sensitivity to HT stress, reflected by the burning symptoms, the degradation of chlorophyll, and the reduction of photosynthetic rates. Additionally, SlBAG9-overexpressing lines showed higher accumulation of lipid peroxidation production (MDA) and H₂O₂, but lower activities of superoxide dismutase, catalase, and peroxidase. Therefore, it is speculated that SlBAG9 plays a negative role in thermotolerance probably by inhibition of antioxidant enzyme system leading to the oxidative damage, consequently aggravating the HT-caused injury phenotype.

The Divergent Roles of the Rice bcl-2 Associated Athanogene (BAG) Genes in Plant Development and Environmental Responses

Bcl-2-associated athanogene (BAG), a group of proteins evolutionarily conserved and functioned as co-chaperones in plants and animals, is involved in various cell activities and diverse physiological processes. However, the biological functions of this gene family in rice are largely unknown. In this study, we identified a total of six BAG members in rice. These genes were classified into two groups, OsBAG1, -2, -3, and -4 are in group I with a conserved ubiquitin-like structure and OsBAG5 and -6 are in group Ⅱ with a calmodulin-binding domain, in addition to a common BAG domain. The BAG genes exhibited diverse expression patterns, with OsBAG4 showing the highest expression level, followed by OsBAG1 and OsBAG3, and OsBAG6 preferentially expressed in the panicle, endosperm, and calli. The co-expression analysis and the hierarchical cluster analysis indicated that the OsBAG1 and OsBAG3 were co-expressed with primary cell wall-biosynthesizing genes, OsBAG4 was co-expressed with phytohormone and transcriptional factors, and OsBAG6 was co-expressed with disease and shock-associated genes. β-glucuronidase (GUS) staining further indicated that OsBAG3 is mainly involved in primary young tissues under both primary and secondary growth. In addition, the expression of the BAG genes under brown planthopper (BPH) feeding, N, P, and K deficiency, heat, drought and plant hormones treatments was investigated. Our results clearly showed that OsBAGs are multifunctional molecules as inferred by their protein structures, subcellular localizations, and expression profiles. BAGs in group I are mainly involved in plant development, whereas BAGs in group II are reactive in gene regulations and stress responses. Our results provide a solid basis for the further elucidation of the biological functions of plant BAG genes.

Characterization of SlBAG Genes from Solanum lycopersicum and Its Function in Response to Dark-Induced Leaf Senescence

The Bcl-2-associated athanogene (BAG) family is a group of evolutionarily conserved cochaperones involved in diverse cellular functions. Here, ten putative SlBAG genes were identified in tomato. SlBAG2 and SlBAG5b have the same gene structure and conserved domains, along with highly similar identity to their homologs in Arabidopsis thaliana, Oryza sativa, and Triticum aestivum. The qPCR data showed that BAG2 and BAG5b were highly expressed in stems and flowers. Moreover, both genes were differentially expressed under diverse abiotic stimuli, including cold stress, heat stress, salt treatment, and UV irradiation, and treatments with phytohormones, namely, ABA, SA, MeJA, and ETH. Subcellular localization showed that SlBAG2 and SlBAG5b were located in the cell membrane and nucleus. To elucidate the functions in leaf senescence of BAG2 and BAG5b, the full-length CDSs of BAG2 and BAG5b were cloned, and transgenic tomatoes were developed. Compared with WT plants, those overexpressing BAG2 and BAG5b had significantly increased chlorophyll contents, chlorophyll fluorescence parameters and photosynthetic rates but obviously decreased ROS levels, chlorophyll degradation and leaf senescence related gene expression under dark stress. Conclusively, overexpression SlBAG2 and SlBAG5b could improve the tolerance of tomato leaves to dark stress and delay leaf senescence.

Molecular Characterization and Expression Profile of PaCOL1, a CONSTANS-like Gene in Phalaenopsis Orchid

CONSTANS (CO) and CONSTANS-like (COL) genes play important roles in coalescing signals from photoperiod and temperature pathways. However, the mechanism of CO and COLs involved in regulating the developmental stage transition and photoperiod/temperature senescing remains unclear. In this study, we identified a COL ortholog gene from the Taiwan native orchid Phalaenopsis aphrodite. The Phalaenopsis aphrodite CONSTANS-like 1 (PaCOL1) belongs to the B-box protein family and functions in the nucleus and cytosol. Expression profile analysis of Phalaenopsis aphrodite revealed that PaCOL1 was significantly expressed in leaves, but its accumulation was repressed during environmental temperature shifts. We found a differential profile for PaCOL1 accumulation, with peak accumulation at late afternoon and at the middle of the night. Arabidopsis with PaCOL1 overexpression showed earlier flowering under short-day (SD) conditions (8 h/23 °C light and 16 h/23 °C dark) but similar flowering time under long-day (LD) conditions (16 h/23 °C light and 8 h/23 °C dark). Transcriptome sequencing revealed several genes upregulated in PaCOL1-overexpressing Arabidopsis plants that were previously involved in flowering regulation of the photoperiod pathway. Yeast two-hybrid (Y2H) analysis and bimolecular fluorescence complementation (BiFC) analysis revealed that PaCOL1 could interact with a crucial clock-associated regulator, AtCCA1, and a flowering repressor, AtFLC. Furthermore, expressing PaCOL1 in cca1.lhy partially reversed the mutant flowering time under photoperiod treatment, which confirms the role of PaCOL1 function in the rhythmic associated factors for modulating flowering.

De novo-based transcriptome profiling of male-sterile and fertile watermelon lines

The whole-genome sequence of watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai), a valuable horticultural crop worldwide, was released in 2013. Here, we compared a de novo-based approach (DBA) to a reference-based approach (RBA) using RNA-seq data, to aid in efforts to improve the annotation of the watermelon reference genome and to obtain biological insight into male-sterility in watermelon. We applied these techniques to available data from two watermelon lines: the male-sterile line DAH3615-MS and the male-fertile line DAH3615. Using DBA, we newly annotated 855 watermelon transcripts, and found gene functional clusters predicted to be related to stimulus responses, nucleic acid binding, transmembrane transport, homeostasis, and Golgi/vesicles. Among the DBA-annotated transcripts, 138 de novo-exclusive differentially-expressed genes (DEDEGs) related to male sterility were detected. Out of 33 randomly selected newly annotated transcripts and DEDEGs, 32 were validated by RT-qPCR. This study demonstrates the usefulness and reliability of the de novo transcriptome assembly in watermelon, and provides new insights for researchers exploring transcriptional blueprints with regard to the male sterility.

Long photoperiod affects the maize transition from vegetative to reproductive stages: a proteomic comparison between photoperiod-sensitive inbred line and its recurrent parent

Maize (Zea mays L.) is a typical short-day plant that is produced as an important food product and industrial material. The photoperiod is one of the most important evolutionary mechanisms enabling the adaptation of plant developmental phases to changes in climate conditions. There are differences in the photoperiod sensitivity of maize inbred lines from tropical to temperate regions. In this study, to identify the maize proteins responsive to a long photoperiod (LP), the photoperiod-insensitive inbred line HZ4 and its near-isogenic line H496, which is sensitive to LP conditions, were analyzed under long-day conditions using isobaric tags for relative and absolute quantitation. We identified 5259 proteins in maize leaves exposed to the LP condition between the vegetative and reproductive stages. These proteins included 579 and 576 differentially accumulated proteins in H496 and HZ4 leaves, respectively. The differentially accumulated proteins (e.g., membrane, defense, and energy- and ribosome-related proteins) exhibited the opposite trends in HZ4 and H496 plants during the transition from the vegetative stage to the reproductive stage. These results suggest that the photoperiod-associated fragment in H496 plants considerably influences various proteins to respond to the photoperiod sensitivity. Overall, our data provide new insights into the effects of long-day treatments on the maize proteome, and may be useful for the development of new germplasm.

The oak gene expression atlas: insights into Fagaceae genome evolution and the discovery of genes regulated during bud dormancy release

BACKGROUND

Many northern-hemisphere forests are dominated by oaks. These species extend over diverse environmental conditions and are thus interesting models for studies of plant adaptation and speciation. The genomic toolbox is an important asset for exploring the functional variation associated with natural selection.

RESULTS

The assembly of previously available and newly developed long and short sequence reads for two sympatric oak species, Quercus robur and Quercus petraea, generated a comprehensive catalog of transcripts for oak. The functional annotation of 91 k contigs demonstrated the presence of a large proportion of plant genes in this unigene set. Comparisons with SwissProt accessions and five plant gene models revealed orthologous relationships, making it possible to decipher the evolution of the oak genome. In particular, it was possible to align 9.5 thousand oak coding sequences with the equivalent sequences on peach chromosomes. Finally, RNA-seq data shed new light on the gene networks underlying vegetative bud dormancy release, a key stage in development allowing plants to adapt their phenology to the environment.

CONCLUSION

In addition to providing a vast array of expressed genes, this study generated essential information about oak genome evolution and the regulation of genes associated with vegetative bud phenology, an important adaptive traits in trees. This resource contributes to the annotation of the oak genome sequence and will provide support for forward genetics approaches aiming to link genotypes with adaptive phenotypes.

Transcriptome analysis by Illumina high-throughout paired-end sequencing reveals the complexity of differential gene expression during in vitro plantlet growth and flowering in Amaranthus tricolor L

Amaranthus tricolor L. is a C4 plant, which is consumed as a major leafy vegetable in some tropical countries. Under conditions of high temperature and short daylight, Am. tricolor readily bolts and blooms, degrading leaf quality. A preliminary in vitro flowering study demonstrated that the flowering control pathway in Am. tricolor may differ from that of Arabidopsis. Nevertheless, no transcriptome analysis of the flowering process in Amaranthus has been conducted. To study Am. tricolor floral regulatory mechanisms, we conducted a large-scale transcriptome analysis--based on Illumina HiSeq sequencing of cDNA libraries generated from Am. tricolor at young seedling (YSS), adult seedling (ASS), flower bud (FBS), and flowering (FS) stages. A total of 99,312 unigenes were obtained. Using BLASTX, 43,088 unigenes (43.39%) were found to have significant similarity with accessions in Nr, Nt, and Swiss-Prot databases. Of these unigenes, 11,291 were mapped to 266 KEGG pathways. Further analysis of the four digital transcriptomes revealed that 735, 17,184, 274, and 206 unigenes were specifically expressed during YSS, ASS, FBS, and FS, respectively, with 59,517 unigenes expressed throughout the four stages. These unigenes were involved in many metabolic pathways related to in vitro flowering. Among these pathways, 259 unigenes were associated with ubiquitin-mediated proteolysis, indicating its importance for in vitro flowering in Am. tricolor. Other pathways, such as circadian rhythm and cell cycle, also had important roles. Finally, 26 unigenes were validated by qRT-PCR in samples from Am. tricolor at YSS, ASS, FBS, and FS; their differential expressions at the various stages indicate their possible roles in Am. tricolor growth and development, but the results were somewhat similar to Arabidopsis. Because unigenes involved in many metabolic pathways or of unknown function were revealed to regulate in vitro plantlet growth and flowering in Am. tricolor, the process appears to be highly complex in this species.