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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., (© 2021. The Author(s).)

Background: Formin, a highly conserved multi-domain protein, interacts with microfilaments and microtubules. Although specifically expressed formin genes in anthers are potentially significant in research on male sterility and hybrid wheat breeding, similar reports in wheat, especially in thermo-sensitive genic male sterile (TGMS) wheat, remain elusive., Results: Herein, we systematically characterized the formin genes in TGMS wheat line BS366 named TaFormins (TaFHs) and predicted their functions in inducing stress response. In total, 25 TaFH genes were uncovered, majorly localized in 2A, 2B, and 2D chromosomes. According to the neighbor-joining (NJ) method, all TaFH proteins from wheat and other plants clustered in 6 sub-groups (A-F). The modeled 3D structures of TaFH1-A/B, TaFH2-A/B, TaFH3-A/B and TaFH3-B/D were validated. And different numbers of stress and hormone-responsive regulatory elements in their 1500 base pair promoter regions were contained in the TaFH genes copies. TaFHs had specific temporal and spatial expression characteristics, whereby TaFH1, TaFH4, and TaFH5 were expressed highly in the stamen of BS366. Besides, the accumulation of TaFHs was remarkably lower in a low-temperature sterile condition (Nanyang) than fertile condition (Beijing), particularly at the early stamen development stage. The pollen cytoskeleton of BS366 was abnormal in the three stages under sterile and fertile environments. Furthermore, under different stress levels, TaFHs expression could be induced by drought, salt, abscisic acid (ABA), salicylic acid (SA), methyl jasmonate (MeJA), indole-3-acetic acid (IAA), polyethylene glycol (PEG), and low temperature. Some miRNAs, including miR167, miR1120, and miR172, interacts with TaFH genes; thus, we constructed an interaction network between microRNAs, TaFHs, phytohormone responses, and distribution of cytoskeleton to reveal the regulatory association between upstream genes of TaFH family members and sterile., Conclusions: Collectively, this comprehensive analysis provides novel insights into TaFHs and miRNA resources for wheat breeding. These findings are, therefore, valuable in understanding the mechanism of TGMS fertility conversion in wheat., (© 2021. The Author(s).)

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.

Background: MYC transcriptional factors are members of the bHLH (basic helix-loop-helix) superfamily, and play important roles in plant growth and development. Recent studies have revealed that some MYCs are involved in the crosstalk between Jasmonic acid regulatory pathway and light signaling in Arabidopsis, but such kinds of studies are rare in wheat, especially in photo-thermo-sensitive genic male sterile (PTGMS) wheat line., Results: 27 non-redundant MYC gene copies, which belonged to 11 TaMYC genes, were identified in the whole genome of wheat (Chinese Spring). These gene copies were distributed on 13 different chromosomes, respectively. Based on the results of phylogenetic analysis, 27 TaMYC gene copies were clustered into group I, group III, and group IV. The identified TaMYC genes copies contained different numbers of light, stress, and hormone-responsive regulatory elements in their 1500 base pair promoter regions. Besides, we found that TaMYC3 was expressed highly in stem, TaMYC5 and TaMYC9 were expressed specially in glume, and the rest of TaMYC genes were expressed in all tissues (root, stem, leaf, pistil, stamen, and glume) of the PTGMS line BS366. Moreover, we found that TaMYC3, TaMYC7, TaMYC9, and TaMYC10 were highly sensitive to methyl jasmonate (MeJA), and other TaMYC genes responded at different levels. Furthermore, we confirmed the expression profiles of TaMYC family members under different light quality and plant hormone stimuli, and abiotic stresses. Finally, we predicted the wheat microRNAs that could interact with TaMYC family members, and built up a network to show their integrative relationships., Conclusions: This study analyzed the size and composition of the MYC gene family in wheat, and investigated stress-responsive and light quality induced expression profiles of each TaMYC gene in the PTGMS wheat line BS366. In conclusion, we obtained lots of important information of TaMYC family, and the results of this study was supposed to contribute novel insights and gene and microRNA resources for wheat breeding, especially for the improvement of PTGMS wheat lines.

Background: COI (CORONATINE INSENSITIVE), an F-box component of the Skp1-Cullin-F-box protein (SCF COI1 ) ubiquitin E3 ligase, plays important roles in the regulation of plant growth and development. Recent studies have shown that COIs are involved in pollen fertility. In this study, we identified and characterized COI genes in the wheat genome and analyzed expression patterns under abiotic stress., Results: A total of 18 COI candidate sequences for 8 members of COI gene family were isolated in wheat (Triticum aestivum L.). Phylogenetic and structural analyses showed that these COI genes could be divided into seven distinct subfamilies. The COI genes showed high expression in stamens and glumes. The qRT-PCR results revealed that wheat COIs were involved in several abiotic stress responses and anther/glume dehiscence in the photoperiod-temperature sensitive genic male sterile (PTGMS) wheat line BS366., Conclusions: The structural characteristics and expression patterns of the COI gene family in wheat as well as the stress-responsive and differential tissue-specific expression profiles of each TaCOI gene were examined in PTGMS wheat line BS366. In addition, we examined SA- and MeJA-induced gene expression in the wheat anther and glume to investigate the role of COI in the JA signaling pathway, involved in the regulation of abnormal anther dehiscence in the PTGMS wheat line. The results of this study contribute novel and detailed information about the TaCOI gene family in wheat and could be used as a benchmark for future studies of the molecular mechanisms of PTGMS in other crops.

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.

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.

A cotton (G. hirsutum L.) dehydration responsive element binding protein gene, GhDREB, which encodes a 153 amino acid protein containing a conserved AP2/EREBP domain, was isolated from the cDNA library of cotton cv. Simian 3 by a yeast one-hybrid system. RNA blot analysis showed that the GhDREB gene was induced in cotton seedlings by drought, high salt and cold stresses. An electrophoretic mobility shift assay (EMSA) indicated that the GhDREB protein bound specifically to the DRE core element (A/GCCGAC) in vitro. Two expression vectors containing the GhDREB gene with either of the Ubiqutin or rd29A promoters were constructed and transferred into wheat (Triticum aestivum L.) by bombardment. Fifty-eight Ubi::GhDREB and 17 rd29A::GhDREB T(0) plants of Yangmai (36 plants) and Lumai (39 plants) were identified by PCR analysis, respectively. Southern blot and RT-PCR analyses showed that two or three copies of the GhDREB were integrated into the Yangmai 10 genome and were expressed at the transcriptional level, and three or four copies were integrated into the Lumai 23 genome. Functional analysis indicated that the transgenic plants had improved tolerance to drought, high salt, and freezing stresses through accumulating higher levels of soluble sugar and chlorophyll in leaves after stress treatments. No phenotype differences were observed between transgenic plants and their non-transgenic controls. These results indicated that GhDREB might be useful in improving wheat stress tolerance through genetic engineering.