抗香蕉枯萎病的野生蕉抗病基因类似序列的克隆与表达

摘要

Wild banana species are essential natural gene pools for banana improvement.In this study,six RGAs about 500 bp were obtained from 1eaves of Musa acuminata,a wild banana shown to be resistant to ba nana Fusarium wilt race 4,by PCR amplification with degenerate primers designed according to the conserved NBS motif and serine/threonine kinase domain of plant resistance(R)genes.Among these RGAs,the deduced amino acids of WNB1 and WNB2 contain NB-ARC do main and WNB1 can be translated into polypeptide uninterrupted by stop codons.The deduced amino acids of other four RGAs (WST1,WST2,WST3 and WST4)all contain the serine/threonine kinase domain and WST3encodes a polypeptide homologous to that of bacterial blight resistance gene Xa21 of rice.At difierent time at ter inoculation with Fusarium oxysporum f.sp.cubense (FOC)race 4,the transcript pattems of WNB1 and WST3 was enhanced,which implied that the expression of WNB1 and WST3 may be related to the resistance of banana to Fusarium wilt.%野生蕉是香蕉遗传改良的天然基因库.为了分离野生蕉中的抗病基因类似序列,根据核苷酸结合位点(nucleotide binding site,NBS)和丝氨酸/苏氨酸蛋白激酶域设计简并性引物,以经过鉴定的抗香蕉枯萎病4号生理小种的野生蕉(Musa acuminata)叶片cDNA为模板进行PCR扩增.经过对扩增产物进行克隆和测序,获得了6个500 bp左右的RGAs片段.其中有2个RGA(WNB1和WNB2)具有NB-ARC保守结构域特征,并且WNB1具有连续的ORF.其余4个RGAs(WST1、WST2、WST3和WST4)均具有丝氨酸/苏氨酸蛋白激酶域特征,且WST3编码的氨基酸序列与水稻抗叶斑病基因Xa21同源性很高.用半定量PCR分析枯萎病菌诱导后野生蕉叶片中RGAs的表达情况,结果表明WNB1和WST3受枯萎病菌诱导后表达量增强,这表明WNB1和WST3的表达可能与香蕉枯萎病抗性相关.