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Physical mapping of a male-fertility gene of common wheat
Abstract
A terminal deletion in the short arm of chromosome 4B was obtained in the progeny of an alien monosomic addition line of common wheat (Triticum aestivum (L.) emend. Thell) with a chromosome from Aegilops cylindrica Host. Common wheat plants homozygous for the deletion were completely male sterile. The breakpoint was at about 84% of the length of the short arm from the centromere. Therefore, the male-fertility gene was located in the distal 16% region of the chromosome 4B short arm. This terminal deletion practically suppressed meiotic pairing between the short arms of the normal 4B and the deletion 4B chromosomes.
... The explanation for this was high male sterility of those lines that lacked 4BS. A fertility gene has been mapped to the short arm of chromosome 4B, and based on previously characterised 4BS deletion lines, the location of the gene on the physical map was estimated to be in the distal 16 % of 4BS (Endo et al. 1991). Moreover, it appeared that a terminal deletion in 4BS of Chinese Spring also interfered with centromere function and suppressed the meiotic pairing in metaphase I between the short arms of the normal 4B and the deletion 4B chromosomes (Endo et al. 1991). ...
... A fertility gene has been mapped to the short arm of chromosome 4B, and based on previously characterised 4BS deletion lines, the location of the gene on the physical map was estimated to be in the distal 16 % of 4BS (Endo et al. 1991). Moreover, it appeared that a terminal deletion in 4BS of Chinese Spring also interfered with centromere function and suppressed the meiotic pairing in metaphase I between the short arms of the normal 4B and the deletion 4B chromosomes (Endo et al. 1991). In the Maringá background, it appears that the fertility gene on 4BS does not have as extreme an effect as in Chinese Spring, and nulli 4B lines still produce grains, even though the grain set is poor. ...
Key message:
Many deletions of the wheat Della ( Rht - B1 ) gene and its flanking regions were isolated in a simple phenotypic screen, and characterised by modified analysis of SNP hybridisation data and cytogenetics. In a dwarf wheat suppressor screen, many tall 'revertants' were isolated following mutagenesis of a severely dwarfed (Rht-B1c) hexaploid wheat. About 150 lines were identified as putative deletions of Rht-B1c, based on the PCR analysis. Southern blot hybridisation established that most of them lacked the Rht-B1 gene, but retained the homoeologues Rht-A1 and Rht-D1. PCR assays were developed for orthologues of two genes that flank Rht-1/Della in the genomes of the model species Brachypodium and rice. Deletion of the B-genome-specific homoeologues of these two genes was confirmed in the Rht-B1 deletion lines, indicating loss of more than a single gene. SNP chip hybridisation analysis established the extents of deletion in these lines. Based on the synteny with Brachypodium chromosomes 1 and 4 g, and rice chromosomes 3g and 11g, notional deletion maps were established. The deletions ranged from interstitial deletions of 4BS through to loss of all 4BS markers. There were also instances, where all 4BS and 4BL markers were lost, and these lines had poor fertility and narrow stems and leaves. Cytogenetic studies on selected lines confirmed the loss of portions of 4BS in lines that lacked most or all 4BS markers. They also confirmed that lines lacking both 4BS and 4BL markers were nullisomics for 4B. These nested deletion lines share a common genetic background and will have applications in assigning markers to regions of 4BS as well as to 4BL. The potential for this type of analysis in other regions of the wheat genome is discussed.
... (ethyl methyl sulfonate, EMS)诱变获得的一个显性突 变体, 距离5A着丝粒3.1 cM, 但与着丝粒之间的物理距 离约为5AS长度的40%, 因此很难通过正向遗传学的方 法进行克隆 [18] ; Ms4也是一个显性核不育基因, 被定位 于小麦4DS末端 [13] , 但后续鲜有相关报道(表1). 隐性基因ms1最早被定位于小麦4BS末端16%的物 理区域内, 后来由两个独立小组通过正向遗传学的方 法成功克隆 [15,17,25] . 变体的表型 [17] . ...
... Depending on the mutation, these can further be divided into dominant and recessive mutants. Dominant mutant loci include Male-sterile (Ms) 2 (4DS), Ms3 (5AS) and Ms4 (4DS) (Bing-Hua and Jing-Yang 1986; Maan et al. 1987;Maan and Kianian 2001) while recessive mutant loci described so far include ms1 (4BS) and ms5 (3AL) (Endo et al. 1991;Klindworth et al. 2002), with seven allelic variations observed for the ms1 locus in different cultivars: ms1a, ms1b, ms1c, ms1d, ms1e, ms1f and ms1g (Suneson 1962;Zhou et al. 2007). Because of their potential use for hybrid breeding, several recent studies have attempted to clone these loci and have proposed breeding schemes towards the deployment of NMS for hybrid breeding (Ni et al. 2017;Tucker et al. 2017;Wang et al. 2017b;Kouidri et al. 2018;Pallotta et al. 2019). ...
Hybrid breeding in wheat (Triticum aestivum L.) has the potential to deliver major yield increases. This is a requisite to guarantee food security for increasing population demands and to counterbalance the effects of extreme environmental conditions. Successful hybrid breeding in wheat relies on forced outcrossing while preventing self-pollination. To achieve this, research has been directed towards identifying and improving fertility control systems. To maximise cross-pollination and seed set, however, fertility control systems need to be complemented by breeding phenotypically distinct male and female lines. This review summarises existing and novel male sterility systems for wheat hybridisation. We also consider the genetic resources that can be used to alter wheat's floral development and spike morphology, with a focus on the genetic variation already available. Exploiting these resources can lead to enhanced outcrossing, a key requirement in the progress towards hybrid wheat breeding.
... Up to now, only five GMS genes have been reported in bread wheat. They are ms1 on 4BS [18], Ms2 on 4DS [19], Ms3 on 5AS [20,21], Ms4 on 4DS [22], and ms5 on 3AL [23]. Among them, ms1 and ms5 are recessive genes, and Ms2, Ms3 and Ms4 are dominant genes. ...
Male sterility is a valuable trait for genetic research and production application of wheat (Triticum aestivum L.). NWMS1, a novel typical genic male sterility mutant, was obtained from Shengnong 1, mutagenized with ethyl methane sulfonate (EMS). Microstructure and ultrastructure observations of the anthers and microspores indicated that the pollen abortion of NWMS1 started at the early uninucleate microspore stage. Pollen grain collapse, plasmolysis, and absent starch grains were the three typical characteristics of the abnormal microspores. The anther transcriptomes of NWMS1 and its wild type Shengnong 1 were compared at the early anther development stage, pollen mother cell meiotic stage, and binucleate microspore stage. Several biological pathways clearly involved in abnormal anther development were identified, including protein processing in endoplasmic reticulum, starch and sucrose metabolism, lipid metabolism, and plant hormone signal transduction. There were 20 key genes involved in the abnormal anther development, screened out by weighted gene co-expression network analysis (WGCNA), including SKP1B, BIP5, KCS11, ADH3, BGLU6, and TIFY10B. The results indicated that the defect in starch and sucrose metabolism was the most important factor causing male sterility in NWMS1. Based on the experimental data, a primary molecular regulation model of abnormal anther and pollen developments in mutant NWMS1 was established. These results laid a solid foundation for further research on the molecular mechanism of wheat male sterility.
... MutMap-Based Cloning of Ms1 in Bread Wheat. Ms1 was formerly mapped to a region encompassing the distal 16% of the short arm of chromosome 4B (4BS) (26). In our study, we used a modified version of the MutMap approach (25) to clone Ms1. ...
Significance
Heterosis provides an important strategy for increasing crop yield, and breeding and adoption of hybrid crops is a feasible way to increase crop yields. Male sterility is an essential trait in hybrid seed production for monoclinous crops, including wheat. Heterosis in wheat was observed approximately 100 y ago. However, very little commercial hybrid wheat is planted in the world because of the lack of a suitable male sterility trait. Therefore, understanding the molecular nature of male fertility in wheat is critical for hybrid wheat development. Here, we report the cloning and molecular, biochemical, and cell-biological characterizations of Male Sterility 1 ( Ms1 ) in bread wheat, and provide a foundation for large-scale commercial hybrid wheat breeding and hybrid seed production.
... Cytogenetic and linkage analysis showed these to be allelic and they were designated as ms1a, ms1b and ms1c, respectively 15,[17][18][19] . In 1976, additional monogenic recessive male steriles were identified from an ethyl methanesulfonate (EMS)-treated population 20 . Three mutants were allelic to ms1, and designated as ms1d, ms1e and ms1f 13, 21 while the fourth mutant was nonallelic to ms1 and designated as ms5 13 . ...
The current rate of yield gain in crops is insufficient to meet the predicted demands. Capturing the yield boost from heterosis is one of the few technologies that offers rapid gain. Hybrids are widely used for cereals, maize and rice, but it has been a challenge to develop a viable hybrid system for bread wheat due to the wheat genome complexity, which is both large and hexaploid. Wheat is our most widely grown crop providing 20% of the calories for humans. Here, we describe the identification of Ms1, a gene proposed for use in large-scale, low-cost production of male-sterile (ms) female lines necessary for hybrid wheat seed production. We show that Ms1 completely restores fertility to ms1d, and encodes a glycosylphosphatidylinositol-anchored lipid transfer protein, necessary for pollen exine development. This represents a key step towards developing a robust hybridization platform in wheat.
... A list of the deletion lines along with the fraction length (FL) of the retained arm is provided as supplementary information in Supplementary Table 1. These deletion lines were generated using gametocidal genes from Aegilops speltoides (38)(39)(40). Giemsa C-banding characterization and low-density restriction fragment length polymorphism (RFLP) mapping suggested that most of these deletion lines resulted from single breaks followed by the loss of the acentric fragments (26,27,40). High-density mapping revealed a few complex and secondary deletions/rearrangements in some of the deletion lines (10). ...
... So far we have been unable to detect and accession of common wheat with compatible allele to Eml-R1b which could be used for the development of a mapping population. Deletion stocks of common wheat give a unique opportunity for genetic analysis in amphidiploids and have been used extensively in mapping different loci ( Endo and Mukai 1988, Endo et al. 1991, Sutka et al. 1999). We used two DT CS lines and a set of partial deletion lines of wheat chromosome 6A for crosses with rye line L2 ( Table 2). ...
The speciation allele at Eml-A1 of hexaploid wheat, which causes embryo lethality in wheat-rye hybrids, was investigated using cytologically modified genetic stocks. It was demonstrated that an extra dose of this allele had no effect on embryo development in these hybrids. There was no positive effect on embryo development and, therefore, no overcoming of the postzygotic barrier. An abortion of the hybrid embryos at an earlier stage of development was also not observed. Physical mapping was performed using chromosome 6A deletion lines. This study revealed the location of Eml-A1 on the most distal part of the long arm of chromosome 6A. To identify possible candidate genes responsible for embryo lethality, in silico sequence homology analysis was performed. Two candidate genes for Eml-A1 that are involved in shoot apical meristem maintenance were identified on chromosome 6AL. However, functional validation assays need to be designed and performed.
... The location of the ms1 gene has been physically mapped to a region comprising the distal 16% of the 4BS chromosome arm (Endo et al., 1991). The dominant male-sterile genes Ms2 and Ms3 are located in chromosome arms 4DS and 5AS, respectively (McIntosh et al., 1998). ...
The paradigm of a 1:1 relationship between cytological chiasmata and genetic crossovers is widely accepted (see Jones, 1987, for review). Extensive literature on meiosis will not be reviewed here, but John (1990) provides a good review of its various aspects. It was Darlington (1932, 1934), who compared chiasma frequencies with genetic map lengths in maize, both for individual chromosomes and the whole genome, and found a good correlation between the two estimators of recombination. With the recent explosion in genetic map construction in diverse organisms using DNA restriction fragment length polymorphisms (RFLPs), genetic maps based on RFLPs far exceed the length expected based on chiasma counts. Nilsson et al., (1993) summarized data from different crop plants documenting the discrepancy between the estimated number of crossovers from chiasma counts or genetic maps (Table 17.1). In every case, chiasma counts underestimated crossover frequencies calculated from recombination data.
The C-banding technique was improved and all 21 chromosomes of two cultivars of common wheat, Triticum aestivum L. were successfully identified. The improved C-banding constantly differentiated a band or bands in all of the wheat chromosomes except 1A: Chromosomes 3D, 4D, 5D, and 6D, which bear no band by N-banding, showed distinctive banding patterns. The other banded chromosomes had banding patterns similar to those differentiated by N-banding. The C-band patterns comprised the bands by N-banding and, in some chromosomes, C-banding specific ones. The two common wheat cultivars showed similar C-banded karyotypes with minor variations.
In this paper we describe the physical properties, sequence divergence and chromosomal distribution of six different repeated sequences in Secale cereale (cultivated rye). All these sequences are located predominantly within blocks of constitutive telomeric heterochromatin which can be observed on all seven pairs of chromosomes of this species by Giemsa staining. The telomeric heterochromatin accounts for 12–18% of the DNA of S. cereale but less than 9% in S. silvestre. Four of the characterized repeats account for most, if not all, of this difference in telomeric heterochromatin DNA amount between the closely related species. These four repeats are present in high copy number in S. cereale DNA but are not detected by various techniques in S. silvestre DNA. The remaining two characterized repeats are common to the two Secale species. Both are arranged in simple tandem arrays with a repeating unit of 120 bp. The major common repeat represents approximately 2.4% of S. cereale DNA and the minor one represents less than 0.2%. The major common repeat is localized in interstitial sites in Secale chromosomes as well as in the telomeric sites. The four S. cereale-specific repeats have several distinguishing physical properties beside their absence in S. silvestre. They are complex. Each contains simple subrepeats interspersed with an unrelated sequence without subrepeats. The major repeat, constituting 5–6% of S. cereale DNA, has a repeat length of 480 bp consisting of a doublet of ∼140 bp interspersed with an unrelated sequence of approximately 230 bp. Another S. cereale repeat representing 2–3% of the total DNA has a repeat unit of 610 bp consisting of a triplet of 110 bp units interspersed with a 280 bp unrelated sequence. Both the 480 and 610 bp repeat families are more homogeneous in sequence, as judged by the thermal stability of duplexes formed in vitro, than the repeat families found in both Secale species. The two remaining S. cereale-specific repeats are related to the minor 120 bp common repeat. One had a repeat unit of 356 bp and consists of two of the 120 bp subrepeats interspersed with an unrelated sequence of 116 bp. The other, a 630 bp repeat, has a 270 bp sequence interspersed with three of the 120 bp subrepeats. We suggest that each of the S. cereale-specific repeats may have evolved by the insertion of DNA elements into an array of simple repeats followed by amplification of the portion of the array containing the inserted sequence.