甘蔗镰孢菌质子偶联寡聚肽转运蛋白基因FsPTR2E的功能研究

Functional analysis of the FsPTR2E gene encoding a proton-coupled oligopeptide transporter in Fusarium sacchari

甘蔗镰孢菌(Fusarium sacchari)是引起甘蔗梢腐病的主要病原菌之一,明确其致病机理对于探寻甘蔗梢腐病防治策略具有重要意义。质子偶联寡聚肽转运蛋白由质子移动力提供能量,转运二肽、三肽等氮源,在生物体生长发育过程中发挥着至关重要的作用。本文对F.sacchari中一个与质子偶联寡聚肽转运蛋白编码基因高度同源的基因FsPTR2E在病菌大型分生孢子形成过程及侵染阶段的表达模式进行分析,同时对FsPTR2E敲除突变体(ΔFsPTR2E)的主要生物学特性进行研究。结果表明,1)同在常规培养基(PDA)上相比,F.sacchari在大型分生孢子诱导培养基上培养24~72 h,FsPTR2E的表达量显著升高;2)F.sacchari侵染寄主72 h时,FsPTR2E的表达量和菌丝阶段相比显著下降;3)敲除FsPTR2E不影响病菌生长、孢子萌发以及对逆境胁迫的响应,但是敲除突变体ΔFsPTR2E的大型分生孢子和小型分生孢子的产量和野生型菌株相比均显著降低;4)ΔFsPTR2E的致病力较野生型菌株显著增强;5)同野生型菌株一样,ΔFsPTR2E可以在以二肽为唯一氮源的培养基上正常生长。这些结果表明FsPTR2E参与了F.sacchari的产孢与致病过程,但可能不负责二肽转运。

Fusarium sacchari is a predominant pathogen causing pokkah boeng disease(PBD)on sugarcane in Guangxi Province,China.Thus,it is of great importance to elucidate the pathogenic mechanism of this pathogen for the development of effective control strategies for PBD prevention.Proton-coupled oligopeptide transporters that transport dipeptide and tripeptide play vital roles in the growth and development of prokaryotic and eukaryotic organisms.In this study,we investigated the expression level of FsPTR2E,a gene encoding a proton-coupled oligopeptide transporter in F.sacchari,during conidiation and infection of its host,and characterized the biological phenotypes of FsPTR2E knockout mutants.The results showed that:1)FsPTR2E was significantly up-regulated on macroconidium-induction medium(SNA+carnation leaf medium)after incubation for 24-72 h,as compared with that incubated on PDA medium;2)the expression level of FsPTR2E was significantly decreased at 72 h post-inoculation onto sugarcane plants compared with that at the mycelial stage;3)deletion of FsPTR2E did not significantly affect mycelial growth,conidial germination and tolerance to stress,but resulted in a significant decrease in macrocondial and microcondial production;4)TheΔFsPTR2E mutant was enhanced in virulence on sugarcane plants compared with the wild-type strain;5)ΔFsPTR2E grew as well as the wild-type strain on media with dipeptides as the only nitrogen source.These results demonstrate that FsPTR2E is involved in sporulation and pathogenicity in F.sacchari but may not be involved in dipeptide transport.