Arabidopsis G-protein ß subunit AGB1 represses abscisic acid signaling via attenuation of the MPK3-VIP1 phosphorylation cascade.

Heterotrimeric G proteins play key roles in cellular processes. Although phenotypic analyses of Arabidopsis Gß (AGB1) mutants have implicated G proteins in abscisic acid (ABA) signaling, the AGB1-mediated modules involved in ABA responses remain unclear. We found that a partial AGB1 protein was localized to the nucleus where it interacted with ABA-activated VirE2-interacting protein 1 (VIP1) and mitogen-activated protein kinase 3 (MPK3). AGB1 acts as an upstream negative regulator of VIP1 activity by initiating responses to ABA and drought stress, and VIP1 regulates the ABA signaling pathway in an MPK3-dependent manner in Arabidopsis. AGB1 outcompeted VIP1 for interaction with the C-terminus of MPK3, and prevented phosphorylation of VIP1 by MPK3. Importantly, ABA treatment reduced AGB1 expression in the wild type, but increased in vip1 and mpk3 mutants. VIP1 associates with ABA response elements present in the AGB1 promoter, forming a negative feedback regulatory loop. Thus, our study defines a new mechanism for fine-tuning ABA signaling through the interplay between AGB1 and MPK3-VIP1. Furthermore, it suggests a common G protein mechanism to receive and transduce signals from the external environment.

Microspore-expressed SCULP1 is required for p-coumaroylation of sporopollenin, exine integrity, and pollen development in wheat.

Sporopollenin is one of the most structurally sophisticated and chemically recalcitrant biopolymers. In higher plants, sporopollenin is the dominant component of exine, the outer wall of pollen grains, and contains covalently linked phenolics that protect the male gametes from harsh environments. Although much has been learned about the biosynthesis of sporopollenin precursors in the tapetum, the nutritive cell layer surrounding developing microspores, little is known about how the biopolymer is assembled on the microspore surface. We identified SCULP1 (SKS clade universal in pollen) as a seed plant conserved clade of the multicopper oxidase family. We showed that SCULP1 in common wheat (Triticum aestivum) is specifically expressed in the microspore when sporopollenin assembly takes place, localized to the developing exine, and binds p-coumaric acid in vitro. Through genetic, biochemical, and 3D reconstruction analyses, we demonstrated that SCULP1 is required for p-coumaroylation of sporopollenin, exine integrity, and pollen viability. Moreover, we found that SCULP1 accumulation is compromised in thermosensitive genic male sterile wheat lines and its expression partially restored exine integrity and male fertility. These findings identified a key microspore protein in autonomous sporopollenin polymer assembly, thereby laying the foundation for elucidating and engineering sporopollenin biosynthesis.

Systematic Analysis and Identification of Drought-Responsive Genes of the CAMTA Gene Family in Wheat (Triticum aestivum L.).

The calmodulin-binding transcription activator (CAMTA) is a Ca2+/CaM-mediated transcription factor (TF) that modulates plant stress responses and development. Although the investigations of CAMTAs in various organisms revealed a broad range of functions from sensory mechanisms to physiological activities in crops, little is known about the CAMTA family in wheat (Triticum aestivum L.). Here, we systematically analyzed phylogeny, gene expansion, conserved motifs, gene structure, cis-elements, chromosomal localization, and expression patterns of CAMTA genes in wheat. We described and confirmed, via molecular evolution and functional verification analyses, two new members of the family, TaCAMTA5-B.1 and TaCAMTA5-B.2. In addition, we determined that the expression of most TaCAMTA genes responded to several abiotic stresses (drought, salt, heat, and cold) and ABA during the seedling stage, but it was mainly induced by drought stress. Our study provides considerable information about the changes in gene expression in wheat under stress, notably that drought stress-related gene expression in TaCAMTA1b-B.1 transgenic lines was significantly upregulated under drought stress. In addition to providing a comprehensive view of CAMTA genes in wheat, our results indicate that TaCAMTA1b-B.1 has a potential role in the drought stress response induced by a water deficit at the seedling stage.

Genome-wide identification and transcriptional characterization of DNA methyltransferases conferring temperature-sensitive male sterility in wheat.

BACKGROUND: DNA methyltransferase (DMT) genes contribute to plant stress responses and development by de novo establishment and subsequent maintenance of DNA methylation during replication. The photoperiod and/or temperature-sensitive genic male sterile (P/TGMS) lines play an important role in hybrid seed production of wheat. However, only a few studies have reported on the effect of DMT genes on temperature-sensitive male sterility of wheat. Although DMT genes have been investigated in some plant species, the identification and analysis of DMT genes in wheat (Triticum aestivum L.) based on genome-wide levels have not been reported. RESULTS: In this study, a detailed overview of phylogeny of 52 wheat DMT (TaDMT) genes was presented. Homoeolog retention for TaDMT genes was significantly above the average retention rate for whole-wheat genes, indicating the functional importance of many DMT homoeologs. We found that the strikingly high number of TaDMT genes resulted mainly from the significant expansion of the TaDRM subfamily. Intriguingly, all 5 paralogs belonged to the wheat DRM subfamily, and we speculated that tandem duplications might play a crucial role in the TaDRM subfamily expansion. Through the transcriptional analysis of TaDMT genes in a TGMS line BS366 and its hybrids with the other six fertile lines under sterile and fertile conditions, we concluded that TaCMT-D2, TaMET1-B1, and TaDRM-U6 might be involved in male sterility in BS366. Furthermore, a correlation analysis showed that TaMET1-B1 might negatively regulate the expression of TaRAFTIN1A, an important gene for pollen development, so we speculated regarding an epigenetic regulatory mechanism underlying the male sterility of BS366 via the interaction between TaMET1-B1 and TaRAFTIN1A. CONCLUSIONS: Our findings presented a detailed phylogenic overview of the DMT genes and could provide novel insights into the effects of DMT genes on TGMS wheat.

Comparative transcriptome and DNA methylation analysis in temperature-sensitive genic male sterile wheat BS366.

BACKGROUND: Known as the prerequisite component for the heterosis breeding system, the male sterile line determines the hybrid yield and seed purity. Therefore, a deep understanding of the mechanism and gene network that leads to male sterility is crucial. BS366, a temperature-sensitive genic male sterile (TGMS) line, is male sterile under cold conditions (12 °C with 12 h of daylight) but fertile under normal temperature (20 °C with 12 h of daylight). RESULTS: During meiosis, BS366 was defective in forming tetrads and dyads due to the abnormal cell plate. During pollen development, unusual vacuolated pollen that could not accumulate starch grains at the binucleate stage was also observed. Transcriptome analysis revealed that genes involved in the meiotic process, such as sister chromatid segregation and microtubule-based movement, were repressed, while genes involved in DNA and histone methylation were induced in BS366 under cold conditions. MethylRAD was used for reduced DNA methylation sequencing of BS366 spikes under both cold and control conditions. The differentially methylated sites (DMSs) located in the gene region were mainly involved in carbohydrate and fatty acid metabolism, lipid metabolism, and transport. Differentially expressed and methylated genes were mainly involved in cell division. CONCLUSIONS: These results indicated that the methylation of genes involved in carbon metabolism or fatty acid metabolism might contribute to male sterility in BS366 spikes, providing novel insight into the molecular mechanism of wheat male sterility.

Transcriptome analysis of wheat seedling and spike tissues in the hybrid Jingmai 8 uncovered genes involved in heterosis.

MAIN CONCLUSION: Transcriptome analysis was carried out for wheat seedlings and spikes from hybrid Jingmai 8 and both inbred lines to unravel mechanisms underlying heterosis. Heterosis, known as one of the most successful strategies for increasing crop yield, has been widely exploited in plant breeding systems. Despite its great importance, the molecular mechanism underlying heterosis remains elusive. In the present study, RNA sequencing (RNA-seq) was performed on the seedling and spike tissues of the wheat (Triticum aestivum) hybrid Jingmai 8 (JM8) and its homozygous parents to unravel the underlying mechanisms of wheat heterosis. In total, 1686 and 2334 genes were identified as differentially expressed genes (DEGs) between the hybrid and the two inbred lines in seedling and spike tissues, respectively. Gene Ontology analysis revealed that DEGs from seedling tissues were significantly enriched in processes involved in photosynthesis and carbon fixation, and the majority of these DEGs expressed at a higher level in JM8 compared to both inbred lines. In addition, cell wall biogenesis and protein biosynthesis-related pathways were also significantly represented. These results confirmed that a combination of different pathways could contribute to heterosis. The DEGs between the hybrid and the two inbred progenitors from the spike tissues were significantly enriched in biological processes related to transcription, RNA biosynthesis and molecular function categories related to transcription factor activities. Furthermore, transcription factors such as NAC, ERF, and TIF-IIA were highly expressed in the hybrid JM8. These results may provide valuable insights into the molecular mechanisms underlying wheat heterosis.

Comprehensive analyses of the annexin gene family in wheat.

BACKGROUND: Annexins are an evolutionarily conserved multigene family of calcium-dependent phospholipid binding proteins that play important roles in stress resistance and plant development. They have been relatively well characterized in model plants Arabidopsis (Arabidopsis thaliana) and rice (Oryza sativa), but nothing has been reported in hexaploid bread wheat (Triticum aestivum) and barely (Hordeum vulgare), which are the two most economically important plants. RESULTS: Based on available genomic and transcriptomic data, 25 and 11 putative annexin genes were found through in silico analysis in wheat and barley, respectively. Additionally, eight and 11 annexin genes were identified from the draft genome sequences of Triticum urartu and Aegilops tauschii, progenitor for the A and D genome of wheat, respectively. By phylogenetic analysis, annexins in these four species together with other monocots and eudicots were classified into six different orthologous groups. Pi values of each of Ann1-12 genes among T. aestivum, T. urartu, A. tauschii and H. vulgare species was very low, with the exception of Ann2 and Ann5 genes. Ann2 gene has been under positive selection, but Ann6 and Ann7 have been under purifying selection among the four species in their evolutionary histories. The nucleotide diversities of Ann1-12 genes in the four species were 0.52065, 0.59239, 0.60691 and 0.53421, respectively. No selective pressure was operated on annexin genes in the same species. Gene expression patterns obtained by real-time PCR and re-analyzing the public microarray data revealed differential temporal and spatial regulation of annexin genes in wheat under different abiotic stress conditions such as salinity, drought, cold and abscisic acid. Among those genes, TaAnn10 is specifically expressed in the anther but fails to be induced by low temperature in thermosensitive genic male sterile lines, suggesting that specific down-regulation of TaAnn10 is associated with conditional male sterility in wheat. CONCLUSIONS: This study analyzed the size and composition of the annexin gene family in wheat and barley, and investigated differential tissue-specific and stress responsive expression profiles of the gene family in wheat. These results provided significant information for understanding the diverse roles of plant annexins and opened a new avenue for functional studies of cold induced male sterility in wheat.

Genome-wide identification and evolutionary analyses of bZIP transcription factors in wheat and its relatives and expression profiles of anther development related TabZIP genes.

BACKGROUND: Among the largest and most diverse transcription factor families in plants, basic leucine zipper (bZIP) family participate in regulating various processes, including floral induction and development, stress and hormone signaling, photomorphogenesis, seed maturation and germination, and pathogen defense. Although common wheat (Triticum aestivum L.) is one of the most widely cultivated and consumed food crops in the world, there is no comprehensive analysis of bZIPs in wheat, especially those involved in anther development. Previous studies have demonstrated wheat, T. urartu, Ae. tauschii, barley and Brachypodium are evolutionarily close in Gramineae family, however, the real evolutionary relationship still remains mysterious. RESULTS: In this study, 187 bZIP family genes were comprehensively identified from current wheat genome. 98, 96 and 107 members of bZIP family were also identified from the genomes of T.urartu, Ae.tauschii and barley, respectively. Orthology analyses suggested 69.4 % of TubZIPs were orthologous to 68.8 % of AetbZIPs and wheat had many more in-paralogs in the bZIP family than its relatives. It was deduced wheat had a closer phylogenetic relationship with barley and Brachypodium than T.urartu and Ae.tauschii. bZIP proteins in wheat, T.urartu and Ae.tauschii were divided into 14 subgroups based on phylogenetic analyses. Using Affymetrix microarray data, 48 differentially expressed TabZIP genes were identified to be related to anther development from comparison between the male sterility line and the restorer line. Genes with close evolutionary relationship tended to share similar gene structures. 15 of 23 selected TabZIP genes contained LTR elements in their promoter regions. Expression of 21 among these 23 TabZIP genes were obviously responsive to low temperature. These 23 TabZIP genes all exhibited distinct tissue-specific expression pattern. Among them, 11 TabZIP genes were predominantly expressed in anther and most of them showed over-dominance expression mode in the cross combination TY806 × BS366. CONCLUSIONS: The genome-wide identification provided an overall insight of bZIP gene family in wheat and its relatives. The evolutionary relationship of wheat and its relatives was proposed based on orthology analyses. Microarray and expression analyses suggested the potential involvement of bZIP genes in anther development and facilitated selection of anther development related gene for further functional characterization.

Identification and characterization of a subset of microRNAs in wheat (Triticum aestivum L.).

MicroRNAs (miRNAs) represent a class of endogenous regulator for post-transcriptionally modulating gene expression. Elucidating complete miRNA repertoires for individual species is a long-desired goal in miRNA research. So far only 42 have been annotated for common wheat (Triticum aestivum) due to its large genome. Here, we employed miRDeep-P, a program developed previously for retrieving miRNAs from deep sequencing data in plants, to parse 14 sequenced small RNA libraries of wheat using expression sequence tags (ESTs) as the reference in lieu of a complete genome sequence. This effort identified 145 miRNAs along with the corresponding stem-looped precursors with many differentially expressed in development and associated with powdery mildew infection. Examination of the phylogenetic distribution of these miRNAs and their target genes revealed that many are conserved in monocots. The set of miRNAs identified in this study is thus useful to further miRNA research in wheat and other important cereal crop species.

ABI-like transcription factor gene TaABL1 from wheat improves multiple abiotic stress tolerances in transgenic plants.

The phytohormone abscisic acid (ABA) plays crucial roles in adaptive responses of plants to abiotic stresses. ABA-responsive element binding proteins (AREBs) are basic leucine zipper transcription factors that regulate the expression of downstream genes containing ABA-responsive elements (ABREs) in promoter regions. A novel ABI-like (ABA-insensitive) transcription factor gene, named TaABL1, containing a conserved basic leucine zipper (bZIP) domain was cloned from wheat. Southern blotting showed that three copies were present in the wheat genome. Phylogenetic analyses indicated that TaABL1 belonged to the AREB subfamily of the bZIP transcription factor family and was most closely related to ZmABI5 in maize and OsAREB2 in rice. Expression of TaABL1 was highly induced in wheat roots, stems, and leaves by ABA, drought, high salt, and low temperature stresses. TaABL1 was localized inside the nuclei of transformed wheat mesophyll protoplast. Overexpression of TaABL1 enhanced responses of transgenic plants to ABA and hastened stomatal closure under stress, thereby improving tolerance to multiple abiotic stresses. Furthermore, overexpression of TaABL1 upregulated or downregulated the expression of some stress-related genes controlling stomatal closure in transgenic plants under ABA and drought stress conditions, suggesting that TaABL1 might be a valuable genetic resource for transgenic molecular breeding.

Cortical functional mechanisms in emotional cognitive tasks in first-episode, drug-naïve with major depressive disorder: A fNIRS study.

BACKGROUND: Previous research has revealed that patients with major depressive disorder (MDD) have negative biases in various aspects of information processing, and these biases are mainly manifested in recognizing facial expressions. However, the link between this emotional cognitive inhibition and neural activation mechanisms in cortical brain regions remains poorly understood. Therefore, this study employed functional near-infrared spectroscopy (fNIRS) to explore the potential impaired regions and neural mechanisms associated with facial emotion cognition in MDD patients. METHODS: 37 MDD patients and 34 healthy controls (HC) were recruited to participate in three sets of cognitive tasks for emotion recognition, and the cortical activation in the brain was synchronously recorded using multi-channel fNIRS. RESULTS: During tasks requiring the motions identification of sad versus happy emotional states, MDD patients exhibit altered activation in both the left frontopolar cortex (FPC) and the right dorsolateral prefrontal cortex (DLPFC). Notably, the FPC demonstrates a higher level of internal coherence and broader correlation with other cortical areas. Moreover, MDD patients showed lower accuracy in distinguishing emotional cues associated with sadness versus those associated with neutral and happy emotions. LIMITATIONS: The study had a relatively small sample size, and it specifically examined only three prevalent facial expressions. CONCLUSION: Facial expression recognition in MDD patients is characterized by negative cognitive interpretation of expressions, which are associated with various cortical altered activations. Neuroimaging further suggests that the cognitive inhibition of emotion signal recognition in everyday interpersonal interactions in MDD patients may primarily be influenced by activation in the left FPC.

A bibliometric analysis of publications on obsessive-compulsive disorder using VOSviewer.

Background: Obsessive-compulsive disorder (OCD) is one of the top ten disabling diseases seriously affecting the health of population. Recently, studies on this disease significantly increased. However, only a few bibliometric analyses concerning this area have been reported. In this study, we used bibliometrics and visualization tools to examine the current state, hot topics and future trends in OCD research. Methods: Scientific publications regarding OCD were retrieved from the Web of Science Core Collection (WoSCC) database. The features of OCD research were further analyzed using VOSviewer. Results: A total of 24,552 publications and 65,296 authors in the field of OCD were retrieved from 2000 to 2022, showing an overall upward trend in publications over the past 22 years. One hundred and thirteen countries around the world had participated in the research. Among these countries, the developed countries such as the United States, England, and Canada were the crucial productive nations in this subject. As for institutions, the Harvard University, the University of London, and the University of California system were the leading institutions. Authors including Storch EA, Mataix-Cols D, and Stein DJ were the prolific authors. 1,949 journals are contributing to the OCD field, of which the top three are Biological Psychiatry (831 articles), European Neuropsychopharmacology (776 articles) and Psychiatric Research (648 articles). Research hotspots of OCD included pathogenesis, epidemiology, comorbidities, clinical features, and evaluation methods. COVID-19, mental health, functional connectivity, and genome-wide association were emerging trends in the field of OCD. Conclusion: This study integrates the bibliometric information on the current research status and emerging trends in OCD from a macro perspective. The findings can provide valuable insights into further research on OCD.

BRI1 EMS SUPPRESSOR1 genes regulate abiotic stress and anther development in wheat (Triticum aestivum L.).

BRI1 EMS SUPPRESSOR1 (BES1) family members are crucial downstream regulators that positively mediate brassinosteroid signaling, playing vital roles in the regulation of plant stress responses and anther development in Arabidopsis. Importantly, the expression profiles of wheat (Triticum aestivum L.) BES1 genes have not been analyzed comprehensively and systematically in response to abiotic stress or during anther development. In this study, we identified 23 BES1-like genes in common wheat, which were unevenly distributed on 17 out of 21 wheat chromosomes. Phylogenetic analysis clustered the BES1 genes into four major clades; moreover, TaBES1-3A2, TaBES1-3B2 and TaBES1-3D2 belonged to the same clade as Arabidopsis BES1/BZR1 HOMOLOG3 (BEH3) and BEH4, which participate in anther development. The expression levels of 23 wheat BES1 genes were assessed using real-time quantitative PCR under various abiotic stress conditions (drought, salt, heat, and cold), and we found that most TaBES1-like genes were downregulated under abiotic stress, particularly during drought stress. We therefore used drought-tolerant and drought-sensitive wheat cultivars to explore TaBES1 expression patterns under drought stress. TaBES1-3B2 and TaBES1-3D2 expression was high in drought-tolerant cultivars but substantially repressed in drought-sensitive cultivars, while TaBES1-6D presented an opposite pattern. Among genes preferentially expressed in anthers, TaBES1-3B2 and TaBES1-3D2 expression was substantially downregulated in thermosensitive genic male-sterile wheat lines compared to common wheat cultivar under sterile conditions, while we detected no obvious differences under fertile conditions. This result suggests that TaBES1-3B2 and TaBES1-3D2 might not only play roles in regulating drought tolerance, but also participate in low temperature-induced male sterility.

A papain-like cysteine protease-released small signal peptide confers wheat resistance to wheat yellow mosaic virus.

Wheat yellow mosaic virus (WYMV), a soil-borne pathogen, poses a serious threat to global wheat production. Here, we identify a WYMV resistance gene, TaRD21A, that belongs to the papain-like cysteine protease family. Through genetic manipulation of TaRD21A expression, we establish its positive role in the regulation of wheat to WYMV resistance. Furthermore, our investigation shows that the TaRD21A-mediated plant antiviral response relies on the release of a small peptide catalyzed by TaRD21A protease activity. To counteract wheat resistance, WYMV-encoded nuclear inclusion protease-a (NIa) suppress TaRD21A activity to promote virus infection. In resistant cultivars, a natural variant of TaRD21A features a glycine-to-threonine substitution and this substitution enables the phosphorylation of threonine, thereby weakening the interaction between NIa and TaRD21A, reinforcing wheat resistance against WYMV. Our study not only unveils a WYMV resistance gene but also offers insights into the intricate mechanisms underpinning resistance against WYMV.

Molecular characterization of novel TaNAC genes in wheat and overexpression of TaNAC2a confers drought tolerance in tobacco.

Plant-specific NAC (NAM/ATAF/CUC) transcription factors (TFs) have been reported to play a role in diverse stress responses and developmental processes. We show here that six new genes encoding NAC TFs in wheat (Triticum aestivum) were identified (named as TaNAC2a, TaNAC4a, TaNAC6, TaNAC7, TaNAC13 and TaNTL5, respectively), and we classified them into three groups: stress-related NACs, development-related NACs and NTLs (membrane-associated TFs belonging to NAC) by phylogenetic analysis. All TaNACs were induced by one or several kinds of stress treatments including dehydration, salinity and low temperature, whereas different genes showed different expression levels. All these TaNACs, except TaNAC7, were proven to have transcriptional activation activity in the yeast strain AH109 by transactivation analysis. Furthermore, subcellular localization analysis revealed that four TaNAC:GFP (green fluorescent protein) fusion proteins were localized in the nucleus, TaNAC2a:GFP mainly located in the nucleus and the plasma membrane, TaNTL5:GFP was associated with the membrane, while truncated TaNTL5(ΔTM):GFP (lacking the transmembrane motif) was detected exclusively in the nucleus. Semi-quantitative reverse transcription polymerase chain reaction analysis demonstrated that five genes exhibited organ-specific expression. Transgenic tobacco plants overexpressing TaNAC2a showed higher fresh weight and dry weight than non-transgenic plants under drought condition, which indicated that the transgene improved tobacco tolerance to drought treatment. Together, these results provided a preliminary characterization of six TaNACs, which possessed a potential role in improving stress tolerance and the regulation of development in wheat, and suggested that TaNAC2a was potentially useful for engineering drought tolerant plants.

The Central Circadian Clock Protein TaCCA1 Regulates Seedling Growth and Spike Development in Wheat (Triticum aestivum L.).

The biological functions of the circadian clock on growth and development have been well elucidated in model plants, while its regulatory roles in crop species, especially the roles on yield-related traits, are poorly understood. In this study, we characterized the core clock gene CIRCADIAN CLOCK-ASSOCIATED 1 (CCA1) homoeologs in wheat and studied their biological functions in seedling growth and spike development. TaCCA1 homoeologs exhibit typical diurnal expression patterns, which are positively regulated by rhythmic histone modifications including histone H3 lysine 4 trimethylation (H3K4me3), histone H3 lysine 9 acetylation (H3K9Ac), and histone H3 lysine 36 trimethylation (H3K36me3). TaCCA1s are preferentially located in the nucleus and tend to form both homo- and heterodimers. TaCCA1 overexpression (TaCCA1-OE) transgenic wheat plants show disrupted circadian rhythmicity coupling with reduced chlorophyll and starch content, as well as biomass at seedling stage, also decreased spike length, grain number per spike, and grain size at the ripening stage. Further studies using DNA affinity purification followed by deep sequencing [DNA affinity purification and sequencing (DAP-seq)] indicated that TaCCA1 preferentially binds to sequences similarly to "evening elements" (EE) motif in the wheat genome, particularly genes associated with photosynthesis, carbon utilization, and auxin homeostasis, and decreased transcriptional levels of these target genes are observed in TaCCA1-OE transgenic wheat plants. Collectively, our study provides novel insights into a circadian-mediated mechanism of gene regulation to coordinate photosynthetic and metabolic activities in wheat, which is important for optimal plant growth and crop yield formation.

The soybean GmbZIP1 transcription factor enhances multiple abiotic stress tolerances in transgenic plants.

Abscisic acid (ABA)-responsive element binding proteins (AREBs) are basic domain/leucine zipper transcription factors that bind to the ABA-responsive element (ABRE) in the promoter regions of ABA-inducible genes in plants. A novel bZIP transcription factor gene, GmbZIP1, encoding 438 amino acids with a conserved bZIP domain composed of 60 amino acids was isolated from salt-tolerant soybean cv. Tiefeng 8. Southern blotting showed that only one copy was present in the soybean genome. Phylogenetic analyses showed that GmbZIP1 belonged to the AREB subfamily of the bZIP family and was most closely related to AtABF2 and OsTRAB1. The expression of GmbZIP1 was highly induced by ABA, drought, high salt and low temperature; and GmbZIP1 was expressed in soybean roots, stems and leaves under different stress conditions. GmbZIP1 was localized inside the nuclei of transformed onion epidermal cells. Overexpression of GmbZIP1 enhanced the responses of transgenic plants to ABA and triggered stomatal closure under stresses, potentially leading to improved tolerances to several abiotic stresses such as high salt, low temperature and drought in transgenic plants. Furthermore, overexpression of GmbZIP1 affected the expression of some ABA or stress-related genes involved in regulating stomatal closure in Arabidopsis under ABA, drought and high salt stress conditions. A few AREB elements were detected in the promoter region of those ABA or stress-related genes, suggesting that GmbZIP1 regulates the ABA response or stomatal closure mediated by those downstream genes in transgenic Arabidopsis. Moreover, GmbZIP1 was used to improve the drought tolerance trait of Chinese wheat varieties BS93. Functional analysis showed that overexpression of GmbZIP1 enhanced the drought tolerance of transgenic wheat, and transcripts of GmbZIP1 were detected in transgenic wheat using RT-PCR. In addition, GmbZIP1 overexpression did not result in growth retardation in all transgenic plants, suggesting that GmbZIP1 may be a valuable genetic resource for engineering stress tolerance of crops.

Visualization and quantification of cadmium accumulation, chelation and antioxidation during the process of vacuolar compartmentalization in the hyperaccumulator plant Solanum nigrum L.

Hyperaccumulators store metals in the vacuoles of leaf cells. To investigate the role of vacuolar compartmentalization in Cd accumulation, chelation and induced antioxidation, we quantified the amounts of total cadmium (Cd), Cd2+, glutathione (GSH) and reactive oxygen species (ROS) in leaf cells of Solanum nigrum L. The results confirmed that vacuoles were, indeed, the main storage compartments for Cd. We then found that with increased Cd treatment concentration, the proportion of vacuolar Cd in protoplasts showed its ultimate storage capacity (82.24 %-83.40 %), and the Cd concentration stored in the protoplast maintained at a certain level (73.81-77.46 mg L-1). Besides, studies on different forms of Cd showed that the chelation state was dominant in the protoplast. The large level appearance of Cd2+ outside the vacuole revealed the limitations of vacuolar Cd2+ sequestration. The relationships between the combined forms of Cd and GSH outside the vacuole (R2 = 0.9906) showed GSH was mainly distributed to important compartments for chelation, not to vacuoles. We also demonstrated the presence of ROS-induced oxidative stress and detoxification mediated by the antioxidant GSH in vacuoles, suggesting that sequestration into vacuoles is an active process accompanied by chelation and antioxidant-mediated detoxification.

Genome-Wide Characterization of OFP Family Genes in Wheat (Triticum aestivum L.) Reveals That TaOPF29a-A Promotes Drought Tolerance.

OVATE family proteins (OFPs) are plant-specific transcription factors that play important roles in plant development. Although common wheat (Triticum aestivum L.) is a major staple food worldwide, OFPs have not been systematically analyzed in this important crop. Here, we performed a genome-wide survey of OFP genes in wheat and identified 100 genes belonging to 34 homoeologous groups. Arabidopsis thaliana, rice (Oryza sativa), and wheat OFP genes were divided into four subgroups based on their phylogenetic relationships. Structural analysis indicated that only four TaOFPs contain introns. We mapped the TaOFP genes onto the wheat chromosomes and determined that TaOFP17 was duplicated in this crop. A survey of cis-acting elements along the promoter regions of TaOFP genes suggested that subfunctionalization of homoeologous genes might have occurred during evolution. The TaOFPs were highly expressed in wheat, with tissue- or organ-specific expression patterns. In addition, these genes were induced by various hormone and stress treatments. For instance, TaOPF29a-A was highly expressed in roots in response to drought stress. Wheat plants overexpressing TaOPF29a-A had longer roots and higher dry weights than nontransgenic plants under drought conditions, suggesting that this gene improves drought tolerance. Our findings provide a starting point for further functional analysis of this important transcription factor family and highlight the potential of using TaOPF29a-A to genetically engineer drought-tolerant crops.

Comprehensive Atlas of Wheat (Triticum aestivum L.) AUXIN RESPONSE FACTOR Expression During Male Reproductive Development and Abiotic Stress.

AUXIN RESPONSE FACTOR (ARF) proteins regulate a wide range of signaling pathways, from general plant growth to abiotic stress responses. Here, we performed a genome-wide survey in wheat (Triticum aestivum) and identified 69 TaARF members that formed 24 homoeologous groups. Phylogenetic analysis clustered TaARF genes into three clades, similar to ARF genes in Arabidopsis (Arabidopsis thaliana) and rice (Oryza sativa). Structural characterization suggested that ARF gene structure and domain composition are well conserved between plant species. Expression profiling revealed diverse patterns of TaARF transcript levels across a range of developmental stages, tissues, and abiotic stresses. A number of TaARF genes shared similar expression patterns and were preferentially expressed in anthers. Moreover, our systematic analysis identified three anther-specific TaARF genes (TaARF8, TaARF9, and TaARF21) whose expression was significantly altered by low temperature in thermosensitive genic male-sterile (TGMS) wheat; these TaARF genes are candidates to participate in the cold-induced male sterility pathway, and offer potential applications in TGMS wheat breeding and hybrid seed production. Moreover, we identified putative functions for a set of TaARFs involved in responses to abscisic acid and abiotic stress. Overall, this study characterized the wheat ARF gene family and generated several hypotheses for future investigation of ARF function during anther development and abiotic stress.