Towards map-based cloning: fine mapping of a recessive genic male-sterile gene (BnMs2) in Brassica napus L. and syntenic region identification based on the Arabidopsis thaliana genome sequences

Abstract

S45AB, a recessive genic male sterile (RGMS) line, originated as a spontaneous mutant in Brassica napus cv. Oro. The genotypes of sterile (S45A) and fertile plants (S45B) are Bnms1ms1ms2ms2 and BnMs1ms1ms2ms2, respectively. In our previous studies, Yi et al. (Theor Appl Genet 113:643-650, 2006) mapped the BnMs1 locus to a region of 0.4 cM, candidates of which have been identified and genetic transformation is in progress. We describe the fine mapping of BnMs2 exploiting amplified fragment length polymorphism (AFLP) and amplified consensus genetic marker (ACGM) methodologies, and the identification of a collinear region probably containing BnMs2 orthologue in Arabidopsis thaliana. A near isogenic line (NIL) population S4516AB which segregated for BnMs2 locus was generated by crossing, allelism testing and repeated full-sib mating. From the survey of 1,024 AFLP primer combinations, 12 tightly linked AFLP markers were obtained and five of them were successfully converted into co-dominant or dominant sequence characterized amplified region (SCAR) markers. A population of 2,650 sterile plants was screened using these markers and a high-resolution map surrounding BnMs2 was constructed. The closest AFLP markers flanking BnMs2 were 0.038 and 0.075 cM away, respectively. Subsequently, an ACGM marker was developed to delimit the BnMs2 locus at an interval of 0.075 cM. We extended marker sequences to perform BlastN searches against the Arabidopsis genome and identified a collinear region containing 68 Arabidopsis genes, in which the orthologue of BnMs2 might be included. We further integrated BnMs2 linked AFLP or SCAR markers to two doubled-haploid (DH) populations derived from the crosses Tapidor x Ningyou7 (Qiu et al., Theor Appl Genet 114:67-80, 2006) and Quantum x No.2127-17 (available in our laboratory), and BnMs2 was mapped on N16. Molecular markers developed from these investigations will facilitate the marker-assisted selection (MAS) of RGMS lines, and the fine map and syntenic region identified will greatly hasten the process of positional cloning of BnMs2 gene.

Molecular markers linked to Bn;rf: a recessive epistatic inhibitor gene of recessive genic male sterility in Brassica napus L.

“…The AFLP marker, XM1, closely linked to the Bn;Rf gene was mapped next to STS marker IGF2021z on top of chromosome 7. Previously, RGMS genes Bn;ms2 (Lei et al 2007), Bn;ms3 (Huang et al 2007;Ke et al 2005) and Bn;ms4 (unpublished information) have been identiWed, which were genetically mapped to N16, N19, N9, respectively. Therefore, the Bn;Rf gene is non-allelic to the three RGMS genes.…”

MS26/CYP704B is required for anther and pollen wall development in bread wheat (Triticum aestivum L.) and combining mutations in all three homeologs causes male sterility

“…These differences suggest dominance, although subtle, of the D-genome over A- and B-genomes for this gene. In contrast, it was observed in Brassica napus that the genotypes BnMs1ms1ms2ms2 and Bnms1ms1Ms2ms2 exhibit wild-type male fertility phenotype [33, 34]. Transcript counts for the three wheat homeologs in anthers showed comparable levels, suggesting that the differences observed in phenotype were not due to differential transcription of the homeologs.…”

Mapping of BnMs4 and BnRf to a common microsyntenic region of Arabidopsis thaliana chromosome 3 using intron polymorphism markers

“…In such an exploiting chromosomal synteny process, intron polymorphism (IP) markers show a powerful force speciWcally in narrowing the candidate region of a target gene. By using an IP marker strategy (Brunel et al 1999;Yang et al 2007), Lei et al (2007) developed a dominant ampliWed consensus genetic marker (ACGM, equivalent to IP marker) more closely linked to BnMs2, which signiWcantly reduce the candidate chromosome interval. However, such applications of synteny may become challenging by the presence of paralogous chromosome segments and the occurrence of small-scale rearrangements and insertions/ deletions within syntenic sequence blocks (Bennetzen 2000;Bennetzen and Ramakrishna 2002).…”

“…Two trapezoids show an inversion of AT C3 in the 304 kb region were also used in mapping genes of Brassica species(Yi et al 2006;Lei et al 2007;He et al 2008; Fig. 4).…”