甘蓝自交不亲和基因MLPK与SSP的FISH定位

利用FISH技术, 对自交不亲和基因MLPK与SSP在甘蓝有丝分裂前中期染色体、减数分裂早粗线期染色体以及伸长DNA纤维等3种分辨率水平的靶DNA载体上进行物理定位。结果表明, 在有丝分裂前中期, MLPK探针信号位于一对近中着丝粒同源染色体的短臂中部, 距着丝粒的百分距离约为53.41±3.16；SSP探针信号位于一对具有随体的近端着丝粒同源染色体的长臂端部, 距着丝粒的百分距离约为78.36±4.26。综合3种载体上的FISH结果表明, MLPK与SSP在甘蓝染色体组中可能都只有一个同源序列座位, 具有在单倍体基因组中的单拷贝性。重复FISH杂交表明, MLPK与5S rDNA位于同一对染色体。依据Armstrong的核型分析标准, 初步判断MLPK与SSP分别位于甘蓝的2号和7号染色体, 与S位点不存在连锁关系。另从比较基因组学角度对定位结果进行了讨论。

Localization of MLPK and SSP Genes for Self-Incompatibility of Brassica oleracea by Fluorescence in situ Hybridization

In Brassica, self-incompatibility recognition is controlled by the multiallelic gene complex (S-haplotypes) at the S-locus, which encodes both the male determinant S-locus pollen coat protein (SCR/SP11) and the female determinant S-locus receptor kinase (SRK). Studies of MLPK and SSP genes for self-incompatibility of Brassica have been gradually widespread since they were identified. However, the position and copy number of MLPK and SSP genes in Brassica oleracea genome are still unclear. In this paper, the localization of MLPK and SSP genes for self-incompatibility of Brassica oleracea on prometaphase chromosomes, early pachytene chromosomes and extended DNA fibers was conducted successfully by fluorescence in situ hybridization. The results indicated that MLPK probe was hybridized onto the short arm of a pair of homologous prometaphase chromosomes, and the percent distance from centromere to the signal point was about 53.41±3.16; SSP probe was hybridized onto the long arm of a pair of homologous prometaphase chromosomes with the satellite, and the percent distance from centromere to the signal point was about 78.36±4.26. Hybridization signals from three kinds of cytological targets with different FISH resolutions showed that both MLPK gene and SSP gene might be located at a single-copy locus in Brassica oleracea genome. Repeated FISH indicated that both MLPK and 5S rDNA probes were hybridized onto the same chromosomes. According to karyotype standard of Armstrong, it was primarily inferred that MLPK gene was located on the chromosome 2, and SSP gene on the chromosome 7. The results presumably revealed thatneither MLPK nor SSP is linked to S-locus. And they locate respectively on the different chromosomes in Brassica oleracea. In addition, the collinearity relationship of MLPK as well as SSP between Brassica and Arabidopsis thaliana was also discussed on the basis of comparative genomics.