苎麻疫霉激发蛋白基因断裂现象初探

苎麻疫霉（PhytophthoraboehmeriaeSaw．）可分泌具有诱抗作用的激发蛋白（α－elicihn），根据α－elicitin第24～30和56～63位保守区氨基酸推导的寡核苷酸引物序列，对苎麻疫霉基因组DNA进行特异PCR扩增反应，发现其扩增的DNA片段大于预计的片段。回收纯化的特异扩增DNA，并进行克隆和测序分析，结果表明特异扩增的elicihn基因亚克隆DNA为570hp，大于预计的117bp。在特异片段中，存在3个内含子将基因断裂成4个阅读框架，即ORF1、ORF2、ORF3和ORF4，其中ORF1和ORF4含有与引物相同的序列，但与其它序列与已克隆的elicihn基因无同源性。因此，芒麻疫霉基因组中的elicitin基因可能存在断裂现象。

SPLIT PHENOMENON OF ELICITIN GENE IN THE GENOME OF PHYTOPHTHORA BOEllMERIAE

Phytophthora boehmeriae Saw. can secrete a proteinaeous elicitors (α -elcihn). based on two conserved regions of the amino acid sequences of α-elcitin (24th to 30th and 56th to 63rd), tWo primers for the amplificatiuon were designed and sythesized. Elicitin gene sequence was amplified from genome DNA of P.boehmeriae designed specific amplified products. This products were purified and cloned into PGEM T easy vector. One positive clone was further characterized by DNA sequence analysis, suggesting that it contained a copy of the 570hp fragment and this fragment was splited into four open reading frames (ORFI, Oaf, ORF3,ORF4) by three nitrons. Among them, ORF1 and ORF4 contained primer sequences respectively, but others were not homology as compared with previoudly sequenced genes. Our results first demonstrated the split phonomenon of elicitin gene, suggesing that multiple forms could occur in the genome of P. boehmeriae.