白梨新S基因的克隆

Cloning of a New Self-incompatibility S-allele in White Pear(Pyrus bretschneideri)

采用PCR-RFLP检测、DNA序列分析和田间杂交试验,从白梨中分离鉴定了1个新的SRNase基因。该SRNase基因PCR扩增产物大小与S8RNase基因PCR产物相似,为450bp左右。但PCR-RFLP和DNA序列分析均表明,它与S8RNase基因存在较大差异,该基因内含子为252bp,而S8RNase的内含子为234bp,并在高变区中具有10个氨基酸出现替换,有两个氨基酸出现缺失。而该SRNase基因却与S12RNase基因具有较高的相似性,在HV区中只有1处碱基被替换,周边区中有10处出现碱基替换或缺失。因此,继梨S18RNase基因,将它命名为S19RNase基因(AY250987)。与S基因型已确定的梨品种的杂交坐果率也说明了该基因是一个新的S-RNase基因。

A new S-RNase gene was identified in white pear （Pyrus bretschneideri） by PCR- RFLP, DNA sequencing analysis and cross pollination tests. The fragment length of PCR amplification using primers specific for S1-RNase to S9-RNase, similar to that of S8-RNase, was around 450 bp. RFLP and DNA sequence analyses revealed that the two genes had great variations in introns and hypervariable （HV） regions. The nucleotide size of intron of this new gene was 252 bp, whereas that of S8-RNase was merely 234 bp. By comparing the amino acids （AA） of the HV regions between the new S-RNase gene and S8-RNase, this new gene had substitutions of 10AA and deletion of 1AA, respectively. Nevertheless, it showed a high identity to S12- RNase that we previously identified in white pear, only 1 bp was substituted in the HV region, and 10 bp were substituted or deleted in the around regions. Based on our current results, the new S-RNase gene was named as S19-RNase （accession number in GenBank： AY250987 ）. The results of reciprocal cross pollination tests between pear cnltivars whose S genotypes have been determined and those containing S19-RNase further confirmed that the isolated fragment was a new S-RNase gene.