普城沙雷氏菌硝吡咯菌素prnA基因突变株的构建

Construction of a prnA mutant in Serratia plymuthica

普城沙雷氏菌(Serratia plymuthica)G3是小麦内生菌,通过合成硝吡咯菌素(Pyrrolnitrin,PRN)抑制植物病原菌。PRN是色氨酸衍生物,通过抑制病原菌呼吸链电子传递系统而具有抗生作用。已报道在假单胞菌和布氏杆菌属中PRN生物合成由prnABCD操纵子控制,需要4个酶PrnA-D顺序作用。而在沙雷氏菌中PRN生物合成还较少有研究。通过基因替换、同源重组策略,构建了G3菌株prnA基因缺失突变体。研究结果表明△prnA突变体不能合成PRN,同时也丧失了对板栗疫病菌Cryphonectria parasitica的拮抗活性,证明prnA基因也是S.plymuthica合成PRN所必需的;也为进一步鉴定抗生素PRN的生物学功能奠定了基础。

Serratia plymuthica G3,an endophytic biocontrol strain,was isolated from the wheat with potential to suppress a variety of plant pathogens due to production of the antibiotic pyrrolnitrin [3-chloro-4-（2-nitro-3-chlorophenyl）-pyrrole,PRN].PRN is a tryptophan-derived secondary metabolite,displays broad-spectrum antagonism through an inhibitory effect on the electron transport system of fungi and bacteria.Previous studies have shown that the prnABCD gene cluster is required for pyrrolnitrin biosynthesis from tryptophan in Pseudomonas and Burkholderia species.However,PRN biosynthetic pathway in Serratia is still poorly understood.In this study,we used gene-replacement strategy to construct a mutant deficient in prnA.Mutation in prnA of G3 abolished production of PRN and antagonistic activity against Cryphonectria parasitica,the causal agent of chestnut blight.The results suggest that prnA is required for PRN biosynthesis in S.plymuthica,and pave the way for the further studies of the PRN function