Sterile Wheat Research Articles

Wheat male-sterile 2 reduces ROS levels to inhibit anther development by deactivating ROS modulator 1

Ms2 is an important dominant male-sterile gene in wheat, but the biochemical function of Ms2 and the mechanism by which it causes male sterility remain elusive. Here, we report the molecular basis underlying Ms2-induced male sterility in wheat. We found that activated Ms2 specifically reduces the reactive oxygen species (ROS) signals in anthers and thereby induces termination of wheat anther development at an early stage. Furthermore, our results indicate that Ms2 is localized in mitochondria, where it physically interacts with a wheat homolog of ROS modulator 1 (TaRomo1). Romo1 positively regulates the ROS levels in humans but has never been studied in plants. We found that single amino acid substitutions in the Ms2 protein that rescue the ms2 male-sterile phenotype abolish the interaction between Ms2 and TaRomo1. Significantly, Ms2 promotes the transition of TaRomo1 proteins from active monomers to inactive oligomers. Taken together, our findings unravel the molecular basis of Ms2-induced male sterility and reveal a regulatory mechanism in which ROS act as essential signals guiding the anther development program in wheat.

Progress in identifying male sterility genes and utilizing heterosis in wheat

<p indent="0mm">Male sterility is a valuable trait for plant breeding and heterosis utilization. Identifying and characterizing male-sterile genes in crops have improved our understanding of the molecular mechanisms controlling anther and pollen grain development, and enabled the development and effective use of many biotechnology-based male sterile systems in hybrid crop breeding. Research progress on male-sterile genes in wheat (<italic>Triticum</italic> spp.) lags that in rice (<italic>Oryza sativa</italic>) and maize (<italic>Zea mays</italic>) because of the polyploid nature and complex genome of wheat; therefore, only a few wheat male-sterile genes have been identified or cloned. Due to the limited progress in understanding the basis of male sterility, a low-cost and efficient wheat hybridization system has not been developed. In this review, we summarize the progress in characterizing genetic male sterility (GMS), cytoplasmic male sterility (CMS), and environment-sensitive GMS (EGMS) in wheat. At least five GMS genes were reported in wheat via forward genetic approaches, of which the dominant gene <italic>Ms2</italic> and the recessive genes <italic>ms1</italic> and <italic>ms5</italic> have been cloned. Furthermore, clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (Cas) gene editing technology was used to characterize the role of four wheat homologs of maize <italic>Ms26</italic> and <italic>Ms45</italic>, rice <italic>NO POLLEN1 </italic>(<italic>OsNP1</italic>), and <italic>Arabidopsis thaliana</italic> <italic>DEFECTIVE IN TAPETAL DEVELOPMENT AND FUNCTION 1 </italic>(<italic>TDF1</italic>) in male fertility. Over 70 different types of wheat CMS systems have been reported; in most cases, CMS is caused by mitochondrial genome rearrangements, and can be reversed with nuclear restorer of fertility (<italic>Rf</italic>) genes. Current approaches to identify wheat <italic>Rf</italic> genes for fertility restoration focus on T-type (<italic>Triticum timopheevii</italic>) and K-type (<italic>Aegilops</italic><italic>kotschyi</italic> Boiss) CMS lines. At least 15 wheat <italic>Rf</italic> genes have been identified, but only two,<italic> Rf1</italic> and <italic>Rf3</italic>, were cloned by genetic mapping and comparative sequence analysis. These two restorer genes and their mode of action in CMS provide new opportunities for wheat hybrid breeding. The candidate CMS restorer genes <italic>Rfk1</italic> and <italic>Rf</italic> ^{<italic>multi</italic>} were also predicted using comparative genomics approaches. EGMS may involve epistatic regulation of non-coding RNAs that restore fertility under specific conditions, and thus provides a special class of germplasm for hybrid production in several crops; however, only a few wheat EGMS genes have been reported and none of them have been cloned. Next, we summarize the wheat hybridization systems that rely on male-sterile genes, such as the “three-line system” based on CMS genes, the “two-line system” based on EGMS genes, and the next generation of hybrid seed production based on nuclear GMS genes. Recent efforts in hybrid wheat breeding have produced hybrid varieties with desirable attributes, which have been marketed in Europe and China. Finally, we discuss future perspectives and challenges in the research and application of next-generation wheat hybrid production technology. This review provides a reference for researching and utilizing male-sterile genes in <italic>Triticeae</italic> crops.

Research progress and prospects of two-line hybrid wheat in China

<p indent="0mm">The effective utilization of wheat heterosis has been a worldwide problem. Since the 1950s, systematic research has mainly focused on the “three-line method” and “chemical killing method” of obtaining hybrid wheat and has not made substantial progress into the present. In the 1990s, two-line hybrid wheat technology created by Chinese scientists based on the discovery and utilization of wheat with photo-thermal-sensitive male sterile germplasm has developed rapidly, making China the only country that uses sterile lines for commercial hybrid wheat production. From the perspective of the whole agroindustrial chain, the research advances of two-line hybrid wheat in China were analyzed and summarized, including germplasm discovery, light-temperature conversion characteristics, genetic mechanisms of wheat photo-thermo-sensitive male sterile lines, selection of male sterile lines, creation of restorer lines, innovation of strong heterotic hybrids, technology for large-scale seed production, and various demonstrations and extensions. The genetic diversity of the photo-thermal-sensitive male sterile lines was examined, and the transformation regulation model of photo-thermo-sensitive male sterility in wheat was thus revealed, indicating that different types of male sterile lines have different restorer genes. The creation of restorer lines through multi restorer gene polymerization and implementing spring × winter wheat hybridization have been illustrated as effective ways to create strongly heterotic hybrids. Taking advantage of hybrid vigor in terms of the ecological synergy, physiological synergy, and temporal and spatial synergy between the parental lines, the invention of the mixed sowing seed production methods, and whole-process mechanization, the seed production yield of two-line hybrid wheat has been greatly improved. Thus, the associated seed production cost has been reduced, laying a critical foundation for the industrial production of hybrid wheat. Here, suggestions and prospects for technological innovation and industrialization of two-line hybrid wheat in China are also described, and it is noted that geographically, ecologically, and genetically distant germplasm should be further utilized to cultivate hybrid wheat varieties with strong advantages. Strengthening the creation of sterile lines and restorer lines with high outcrossing rates, high resilience, and high combining ability and greatly improving the yield of seed production are the keys to future research and development of hybrid wheat. It is clear that this is an important period of opportunity for the research and application of China’s hybrid wheat to achieve leapfrog development. It is of great strategic importance for China to maintain its international leading position in hybrid wheat development and production as well as seize the commanding heights of the international seed industry of hybrid wheat and ensure national food security.

Research progress and reflection of two-line hybrid wheat based on thermo-photo sensitive genic male sterility in Yunnan

<p indent="0mm">Wheat is one of the most important food crops in Yunnan Province. Drought and yellow rust are the main limiting factors to wheat productivity. Utilization of heterosis is expected to be a promising way to increase resistance to stress and yield potential. In 1992, photo-thermo sensitive genic male sterile wheat “ES” and thermo-photo sensitive genic male sterile wheat “C49S” were developed by Hunan Agricultural University and Chongqing Academy of Agricultural Science, respectively, which provided a new way for heterosis utilization in China by conducting two-line hybrid wheat breeding. ES and C49S were sterile under low-temperature and short-day conditions, and fertile under high-temperature and long-day conditions. During 1993–2000, ten sterile lines of ES and C49S were introduced into Yunnan for sterility identification, while only C49S-87 from Chongqing showed stable sterility in three special locations of Yunnan when sowed in middle October, with 15–20 d of sterile heading duration (bagged seed-set rate &lt;1%). In 2002, hybrid cultivar Yunza 3 from C49S-87 was released in Yunnan and increased yield by 11.4% over the inbred CK in regional tests, but was planted only 12400 ha in Yunnan due to the loss of resistance to yellow rust after 2004. Given that C49S-87 was poor in out-crossing ability (40%–50%) and susceptible to yellow rust, an improved sterile line K78S was developed from C49S-87 in 2001. K78S had 26–44 d of sterile heading duration in all regions with altitudes from <sc>1530</sc> to <sc>2400 m</sc> when sowed from middle October to early November, as well as better out-crossing ability (70%–80%) and higher resistance to yellow rust. In 2004 and 2005, Yunza 5 and Yunza 6 developed from K78S were separately released in Yunnan. Both cultivars showed higher yield increase by &gt;15% in regional tests. Meanwhile, high cross-pollination ability of K78S markedly raised the yield of hybrid seed production from 1500–1800 kg/ha of Yunza 3 to 3900–4500 kg/ha of Yunza 5 and Yunza 6 when the same techniques of mechanized seed production were applied. These cultivars have been totally planted about 700000 ha in Yunnan and parts of Vietnam till now. However, since 2005, no hybrid cultivar has been released in Yunnan. The main reasons are as follows: (1) Only two sterile lines were practically used for test-crossing before 2020 but became susceptible to yellow rust ten years ago, which greatly reduced the opportunities of creating high heterotic hybrids although thousands of restorers were test-crossed. In 2020, 24 elite sterile lines were developed by using doubled haploid (DH) breeding, and have been used in hybrid wheat breeding now. (2) Most restorers were “by-products” of developing inbred cultivars, thus the combining ability between the sterile line and the restorer was never tested during the developing of restorers, resulting in completely random or accidental emergence of heterotic hybrids. Therefore, it might be necessary to re-construct the restorer breeding program by using dwarf-male-sterile wheat with reference to maize inbred line breeding. In addition, exploitation of nucleo-cytoplasmic heterosis might be another way to increase heterosis both in yield potential and resistance to stress, as suggested by Kihara in 1979. Generally, some promising progress in two-line hybrid wheat breeding based on thermo-photo sensitive genic male sterility has been achieved in Yunnan during past <sc>30 years.</sc> However, more efforts should be made in breeding and basic research to efficiently create hybrids with higher yield increase and better resistance to drought and diseases, and this will improve the current system and promote the wider application of hybrid wheat in Yunnan.

Proteomic and Phosphoproteomic Analyses Reveal a Complex Network Regulating Pollen Abortion and Potential Candidate Proteins in TCMS Wheat.

Thermosensitive sterile lines are natural materials for exploring the effects of anther development on male fertility. To study the possible molecular mechanisms regulating protein activity during the induction of male sterility, proteomic and phosphoproteomic analyses with tandem mass tags (TMTs) were used to study the binucleate anther of the thermosensitive sterile wheat line YS3038. A total of 9072 proteins, including 5019 phosphoproteins, were identified. Enrichment analyses of differentially abundant proteins (DAPs) and phosphoproteins (DAPPs) in metabolic pathways showed that both were mainly related to energy metabolism. Soluble sugar and ATP content were significantly decreased, free fatty acid content was significantly increased, and ROS was abnormally accumulated in male sterile YS3038-A. In addition, 233 kinase–substrate pairs involved in potential phosphorylation control networks were predicted to regulate fertility. Candidate proteins were identified, and a quantitative real-time polymerase chain reaction (qRT-PCR) analysis was used to validate the TMT results. TaPDCD5 is likely to be involved in fertility conversion of YS3038 by barley stripe mosaic virus-induced gene silencing (BSMV-VIGS). Our data provide new insights into the mechanism of TCMS, which has value for identifying potential candidate proteins associated with the formation or abortion of pollen and promotion of wheat heterosis utilization.

The gene TaPG encoding a polygalacturonase is critical for pollen development and male fertility in thermo-sensitive cytoplasmic male-sterility wheat

Thermo-sensitive cytoplasmic male sterility is of great significance to heterosis and hybrid seed production in wheat. Consequently, it is worthwhile to research the genes associated with male sterility. Although polygalacturonases (PGs) have been studied to play a crucial role in male reproduction of many plants, their functions in the reproductive development of wheat remain unclear. Here, TaPG (TraesCS7A02G404900) encoding a polygalacturonase was isolated from the anthers of KTM3315A, a wheat thermo-sensitive cytoplasmic male sterile with Aegilops kotschyi cytoplasm. Expression pattern analyses showed that TaPG was strongly expressed in fertile anthers and its protein was localized in the cell wall. Further verification via barley stripe mosaic virus revealed that the silencing of TaPG exhibited abnormal anthers, premature degradation of tapetum, pollen abortion, and defective pollen wall formation, resulting in the declination of fertility. Conclusively, our research suggested that TaPG contributed to the pollen development and male fertility, which will provide a novel insight into the fertility conversion of thermo-sensitive cytoplasmic male sterility in wheat.

First Report of Collar and Root Rot of Faba Bean Caused by Rhizoctonia solani AG-2-2 IIIB in Bangladesh.

Faba bean (Vicia faba L.) is an underutilized promising grain legume commercially grown in central and northern part of Bangladesh (Yasmin et al. 2020). In January 2021, faba bean plants exhibiting symptoms of collar and root rot and yellowing of leaves were observed in thirty plots of an experimental field at the Bangladesh Agricultural University (24.75° N, 90.50° E), Mymensingh, Bangladesh. Infected plants had dark brown to black lesions on the roots, extending above the collar region. An average disease incidence and severity was 7.16% and 6.91%, respectively. Eight diseased plants were collected from the field by uprooting one plant from each of eight randomly selected experimental plots and surface disinfected with sodium hypochlorite (0.2%) for 3 min followed by 1 min in ethanol (70%), and then rinsed three times with distilled water and dried on sterile paper towels. Collar and root pieces (5×5 mm) of symptomatic tissues were placed on Potato Dextrose Agar (PDA). Plates were incubated at 25°C for three days and isolates were purified from single-tip culture. The isolates produced brown colored mycelia often with brown sclerotia. Under microscope, fungal colonies exhibited right-angled branching with constriction at the base of hyphal branches and a septum near the originating point of hyphal branch consistent with the description of Rhizoctonia solani Kuhn (Sneh et al. 1991). The isolates grew at 35°C on PDA (5 mm/24). Molecular identification of the isolates BTRFB1 and BTRFB7 was determined by sequencing the rDNA internal transcribed spacer (ITS) region using primers ITS1 and ITS4 (White et al. 1990). A BLAST search showed that the sequences (GenBank Accession nos. MZ158299.1 and MZ158298.1) had 99.28% similarity with R. solani isolates Y1063 and SX-RSD1 (GenBank Accession nos. JX913811.1 and KC413984.1, respectively). Phylogenetic analysis revealed that the present isolates grouped with R. solani anastomosis group AG-2-2 IIIB. To confirm pathogenicity, both isolates were grown individually on sterile wheat kernels at 28°C for 6 days (D'aes et al. 2011). Faba bean seedlings were grown in plastic pots containing sterile potting mix (field soil/composted manure/sand 2:2:1 [v/v]). Two-week-old plants were inoculated by placing five infested wheat seeds adjacent to the roots. Control pots were inoculated with sterile wheat kernels using the same procedure. Plants were placed in a growth room with a 16 h/8 h light/dark photoperiod at 25 ± 2°C after inoculation. Fifteen days after inoculation, typical collar and root rot symptoms were developed on inoculated plants, similar to symptoms observed in the field. Control plants remained non-symptomatic. Finally, six isolates of R. solani were isolated from the symptomatic plants and identified by morphological and molecular analysis. Rhizoctonia solani is the causal agent of seed and root rot, hypocotyl canker, and seedling damping-off diseases of faba bean in many other countries (Rashid and Bernier 1993; Assunção et al. 2011). To our knowledge, this is the first confirmed report of Rhizoctonia solani causing collar and root rot of faba bean in Bangladesh. This finding will be helpful for the development of management strategies to control this disease and to expand the production of faba bean in Bangladesh.

First Report of Root Rot of Tobacco Caused by Fusarium brachygibbosum in China.

Tobacco (Nicotiana tabacum L.) is an important cash crop in China, with an estimated production of 2.2 million tons every year (Berbeć and Matyka, 2020). In June 2020, a root rot disease was observed on tobacco (cv. Zhongyan 100) in four surveyed counties (Mianchi, Lushi, Duguan and Lingbao) in Sanmenxia. Diseased plants exhibited leaf chlorosis and purplish to brown vascular discoloration of stem, taproot and lateral roots. The disease incidence ranged from 15% to 40% in 11 surveyed fields, 36.7 ha in total. Twenty five diseased tissues were surface sterilized in 75% ethanol and placed on potato dextrose agar (PDA) medium. Fifteen single-spore isolates were obtained from 25 diseased tissue samples. All cultures growing on PDA had white colonies with abundant aerial mycelia initially, turning into yellow to orange in the center and produced red pigmentation after seven days of growth. The 7-day-old cultures grown on carnation leaf agar (CLA) produced macroconidia that were curved with 3-5 septa, had wide central cells, slightly pointy apex, and measured 17.0-45.9 μm long×3.0-4.6 μm wide (n=50). The microconidia formed on CLA were slightly curved, ovoid with zero to two septa, measuring 5.4-15.5 μm long×2.0-3.2 μm wide (n=50). Spherical chlamydospores (7.58-13.52 μm; n=50) were terminal or intercalary, single or in chains. Such characteristics were typical of Fuarium brachygibbosum (Tirado-Ramírez et al. 2018). DNA from one representative single-spore isolate (MC1) was extracted, and the translation elongation factor 1-alpha (EF1-α), RNA polymerase I largest subunit (RPB1) and second largest subunit (RPB2) genes were amplified with primers EF1/EF2, F5/G2R and RPB2F/R respectively (O'Donnell et al. 1998, 2010), and sequenced. Sequences were submitted to GenBank under accession numbers MT947796 (EF1-α), MW679536 (RPB1) and MW430664 (RPB2). The consensus sequences showed 99.70%, 99.94% and 100% identity to the sequences of F. brachygibbosum strain NRRL 34033 (accession no. GQ505418.1, HM347172.1 and GQ505482.1, Wang et al 2021). Morphological and molecular results confirmed this species as F. brachygibbosum (Al-Mahmooli, et al., 2013, Rentería -Martínez, et al., 2018). Pathogenicity tests were performed on tobacco seedlings grown on autoclaved tobacco specific substrate (Tobacco specific matrix, Ainong Biotechnology Co. Ltd, China). Healthy six-leaf stage tobacco seedlings (n=30; Zhongyan 100) were inoculated by placing 7-days old wheat seed (15 seeds per plant) infested with MC1 around the root. Thirty seedlings inoculated with sterile wheat seeds served as controls. All the plants were maintained in a growth chamber at 25±0.5℃ and 70% relative humidity. The assay was conducted three times. Typical symptoms of foliage chlorosis and root browning were observed 7-14 days after inoculation. The pathogen was reisolated from the necrotic tissue from all inoculated seedlings and was identified by sequencing partial EF1-α and RPB2 genes. Control plants remained asymptomatic and no pathogen was recovered from the control plants. Fusarium brachygibbosum is known as a pathogen of grains and cash crops in China (Shan, et al., 2017, Xia, et al., 2018). To our knowledge, this is the first report of F. brachygibbosum causing root rot on tobacco. We believe that our results will help to better understand rhizome fungal diseases affecting tobacco production in China. Acknowledgements: Funding was provided by the Science and Technology Project of Henan Provincial Tobacco Company (2020410000270012), Independent Innovation Project of Hennan Academy of Agricultural Sciences (2020ZC18) and Research and Development project of Henan Academy of Agricultural Sciences (2020CY010).

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

BackgroundKnown 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).ResultsDuring 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.ConclusionsThese 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.

Global survey of alternative splicing and gene modules associated with fertility regulation in a thermosensitive genic male sterile wheat

Thermosensitive genic male sterile (TGMS) wheat lines are the core of two-line hybrid systems. Understanding the mechanism that regulates male sterility in TGMS wheat lines is helpful for promoting wheat breeding. Several studies have obtained information regarding the mechanisms associated with male sterility at the transcriptional level, but it is not clear how the post-transcriptional process of alternative splicing might contribute to controlling male sterility. In this study, we performed genome-wide analyses of alternative splicing during the meiosis stage in TGMS line BS366 using PacBio and RNA-Seq hybrid sequencing. Cytological observations indicated that cytoskeleton assembly in pollen cells, calcium deposition in pollen and tapetal cells, and vesicle transport in tapetal cells were deficient in BS366. According to our cytological findings, 49 differentially spliced genes were isolated. Moreover, 25 long non-coding RNA targets and three bHLH transcription factors were identified. Weighted gene co-expression network analysis detected four candidate differentially spliced genes that had strong co-relation with the seed setting percentage, which is the direct representation of male sterility in BS366. In this study, we obtained comprehensive data regarding the alternative splicing-mediated regulation of male sterility in TGMS wheat. The candidates identified may provide the molecular basis for an improved understanding of male sterility.

First Report of Rhizoctonia solani AG2-1 on roots of wheat in Kazakhstan.

In June 2019, approximately 20 tillers of wheat (Triticum aestivum L.) were sampled at the ripening stage (Feekes scale 11) from four different fields in Almaty, Kazakhstan. Brown lesions (3-5 mm in length) were present on the roots of sampled plants, with 20% incidence. To determine the causal agent, diseased roots were surface disinfected in sodium hypochlorite solution (1%) for 3 min, rinsed triple with sterile distilled water, air-dried in a laminar flow hood, and plated onto one-fifth strength potato dextrose agar (PDA) supplemented with 50 ppm chloramphenicol. After three days, the hyphal fragments that developed from the sections were transferred to fresh PDA and incubated at 23°C with 12-h photoperiod for 7 days to obtain pure cultures. Brown pigmented fungal colonies with a constriction at the base of hyphal branches, septa near the branching point, and right-angled branching resembling Rhizoctonia solani were observed. The identification anastomosis group (AG) of a representative isolate for each field was conducted by sequencing the internal transcribed spacer (ITS) region of rDNA with the universal primers ITS4 and ITS5 (White et al. 1990). The resulting sequences of 693 bp length were deposited in GenBank (accession nos. MW898143:MW898146). These sequences were 100% identical to the isolate 8Rs of R. solani AG2-1 (accession no. AF354063). To confirm the pathogenicity of the four isolates, the colonized wheat kernels method described by Demirci (1998) was used to inoculate a sterile potting mix containing peat, vermiculite, and soil (1:1:1 by v/v/v) into which wheat (cv. Seri) was planted. Control pots were inoculated with sterile wheat kernels using the same procedure. Wheat plants were left to grow for four weeks under controlled environmental conditions with a 23°C temperature regime. During the period that the plants remained in the glasshouse, the typical light regime was 16 h. Brown lesions were observed on the roots of plants in the inoculated pots whereas no symptoms were observed on plants grown in the control pots. R. solani was consistently reisolated from symptomatic plants, thereby confirming Koch's postulates. To our knowledge, this is the first report of R. solani AG2-1 on roots of wheat in Kazakhstan. R. solani AG2-1 isolates have been previously reported to be a weak pathogen to wheat (Roberts and Sivasithamparam 1986; Sturrock et al. 2015; Jaaffar et al. 2016; Özer et al. 2019). We suggest further studies are required to characterize the impact of R. solani AG2-1 in wheat. Considering crop rotation, the selection of non-host crops to this AG group is important to pathogen management, by reducing the amount of inoculum in the soil.

Comprehensive analysis of formin gene family highlights candidate genes related to pollen cytoskeleton and male fertility in wheat (Triticum aestivum L.)

BackgroundFormin, 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.ResultsHerein, 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.ConclusionsCollectively, 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.

Characterization of the Mitochondrial Genome of a Wheat AL-Type Male Sterility Line and the Candidate CMS Gene.

Heterosis utilization is very important in hybrid seed production. An AL-type cytoplasmic male sterile (CMS) line has been used in wheat-hybrid seed production, but its sterility mechanism has not been explored. In the present study, we sequenced and verified the candidate CMS gene in the AL-type sterile line (AL18A) and its maintainer line (AL18B). In the late uni-nucleate stage, the tapetum cells of AL18A showed delayed programmed cell death (PCD) and termination of microspore at the bi-nucleate stage. As compared to AL18B, the AL18A line produced 100% aborted pollens. The mitochondrial genomes of AL18A and AL18B were sequenced using the next generation sequencing such as Hiseq and PacBio. It was found that the mitochondrial genome of AL18A had 99% similarity with that of Triticum timopheevii, AL18B was identical to that of Triticum aestivum cv. Chinese Yumai. Based on transmembrane structure prediction, 12 orfs were selected as candidate CMS genes, including a previously suggested orf256. Only the lines harboring orf279 showed sterility in the transgenic Arabidopsis system, indicating that orf279 is the CMS gene in the AL-type wheat CMS lines. These results provide a theoretical basis and data support to further analyze the mechanism of AL-type cytoplasmic male sterility in wheat.

Plant breeding: Revealing the secrets of cytoplasmic male sterility in wheat

While cytoplasmic male sterility is used for breeding in many crops, it has proved difficult to implement in wheat. A new study identifying the key molecules and their mode of action in cytoplasmic male sterility provides new opportunities for wheat breeding.

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

BackgroundDNA 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.ResultsIn 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.ConclusionsOur findings presented a detailed phylogenic overview of the DMT genes and could provide novel insights into the effects of DMT genes on TGMS wheat.

Reproductive fitness of five Pratylenchus thornei populations from Isparta Province in Turkey on sterile carrot discs, wheat and barley cultivars

In the study, five populations of Pratylenchus thornei which obtained from different locations in Isparta Province in Turkey were investigated for their reproductive fitness on carrot discs and wheat varieties of Ikizce and Altay and barley varieties of Tarm92 and Burakbey. Reproductive fitness evaluated as the ratio of the final number of nematodes to the number of nematodes inoculated. There was a significant difference in reproductive fitness among the five P. thornei populations on carrot discs. The highest reproductive fitness on carrot discs was obtained with the P. thornei populations of SK11 and SK24 whereas pathogenicity of these populations was differentiated among wheat and barley varieties. The highest reproductive fitness was found at SK11 population with all wheat and barley varieties. GD18 and ISP10 populations developed better in barley than in wheat varieties. This study showed that there might be differences in reproduction of populations of the same nematode species isolated from different geographical areas.

Identification and verification of genes related to pollen development and male sterility induced by high temperature in the thermo-sensitive genic male sterile wheat line.

Bioinformatic analysis identified the function of genes regulating wheat fertility. Barley stripe mosaic virus-induced gene silencing verified that the genes TaMut11 and TaSF3 are involved in pollen development and related to fertility conversion. Environment-sensitive genic male sterility is of vital importance to hybrid vigor in crop production and breeding. Therefore, it is meaningful to study the function of the genes related to pollen development and male sterility, which is still not fully understand currently. In this study, YanZhan 4110S, a new thermo-sensitive genic male sterility wheat line, and its near-isogenic line YanZhan 4110 were analyzed. Through comparative transcriptome basic bioinformatics and weighted gene co-expression network to further identify some hub genes, the genes TaMut11 and TaSF3 associated with pollen development and male sterility induced by high-temperature were identified in YanZhan 4110S. Further verification through barley stripe mosaic virus-induced gene silencing elucidated that the silencing of TaMut11 and TaSF3 caused pollen abortion, finally resulting in the declination of fertility. These findings provided data on the abortive mechanism in environment-sensitive genic male sterility wheat.

Antifungal effect of volatile organic compounds produced by Streptomyces salmonis PSRDC-09 against anthracnose pathogen Colletotrichum gloeosporioides PSU-03 in postharvest chili fruit.

Application of volatile organic compounds (VOCs) from Streptomyces salmonis PSRDC-09 (VOCs PSRDC-09) grown on sterile wheat seeds against chili anthracnose pathogen was investigated in vitro and in vivo. Among 10 isolates of Colletotrichum species tested, Colletotrichum gloeosporioides PSU-03 was selected as the most aggressive anthracnose pathogenic strain on chili fruit against VOCs produced by Streptomyces species. Among 11 isolates, the strain PSRDC-09 exhibited the highest antifungal activity and was identified as S. salmonis PSRDC-09. The antagonistic mechanism of the VOCs PSRDC-09 on morphological of C. gloeosporioides PSU-03, observed by scanning electron microscope (SEM), revealed the irregular distortions in the fungal hyphae. The effect of inoculum size and spore concentration of S. salmonis PSRDC-09 prepared as a wheat seed inoculum on the suppression of C. gloeosporioides PSU-03 was studied both in vitro and on chili fruit. The optimum inoculum size (45g 0·31l-1 ) and spore concentration (107 spores per ml) of the wheat seed culture of S. salmonis PSRDC-09 exhibited the complete suppression (100% inhibition) on C. gloeosporioides PSU-03. The optimum fumigation period of the VOCs PSRDC-09 (45g 1·38l-1 ) was found to be 24h. Based on gas chromatography-mass spectrometry (GC-MS) analysis, 14 major VOCs (produced by the strain PSRDC-09) were detected and l-linalool was the main volatile component. The results indicated that the VOCs from S. salmonis PSRDC-09 could effectively control the chili anthracnose disease caused by C. gloeosporioides. These findings suggest that S. salmonis PSRDC-09 may have the potential to become a promising biofumigant for biocontrol of chili anthracnose disease in the postharvest system.

Uncovering ceRNA integrated networks that associate with fertility in a photoperiod and temperature sensitive male sterile wheat line

The pollen fertility of photoperiod/temperature sensitive genic male sterile (P/TGMS) wheat is controlled by light and/or temperature. Circular RNA (circRNA) and long non-coding RNA (lncRNA) are known to participate in the development of anthers in plants, but their impact on male sterility in the P/TGMS line is not well understood. In this study, we carried out high-throughput sequencing to investigate the differential expression of lncRNAs and circRNAs and their biological functions in anthers of photo-thermosensitive genic male sterile (PTGMS) wheat line BS366-42L during the transition phase of male fertility under four different photoperiod and temperature treatments. Eight lncRNAs, 40 mRNAs and three circRNAs were screened out and thought as essential candidates that closely related to male sterility. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed to predict the potential functions of differentially expressed RNAs. The results indicated that carbohydrate-related metabolism was important for male sterility in the wheat PTGMS line BS366-42L. lncRNA/circRNA-mRNA-miRNA (ceRNA) integrate networks were constructed to reflect their complex inner association with male sterility. Our study provides a systematic perspective on the potential function of RNAs in male fertility in PTGMS lines of wheat.

Fertility recovery of wheat male sterility controlled by Ms2 using CRISPR/Cas9.

Fertility recovery of wheat male sterility controlled by Ms2 using CRISPR/Cas9.