ib101206 - proteome data analysis

P2 is a spontaneous mutant selected from P1, an entomopathogenic fungus Beauveria bassiana that hyper-produces extracellular protease(s), compared to P1. The major expressed serine protease, called SBP, is shown to be up-regulated at the transcriptional level in the P2 mutant strain. The insecticidal potential of P1 and P2 strains was evaluated against Tuta absoluta larvae under laboratory conditions. Both strains are effective but P2 showed stronger effect than P1. Median lethal concentration (LC50) of P2 is 26 fold lower than that of P1. Median lethal times (LT50) of P1 and P2 are 4.38 and 0.84 days using 105 conidia ml-1. Enzymatic assays analysis showed that extracellular enzymes are differently expressed by the two strains, especially proteases and chitinases. Two-dimensional gel electrophoresis and mass spectrometry analysis confirmed the overexpression by P2 strain of protease and chitinase and revealed further the over-expression of several protease isoforms. Here we show a direct link between fungal enzymatic profile and insect’s pathogenesis, giving a molecular explanation for the insecticidal potential of B. bassiana fungus.

P2为从P1中筛选获得的自发突变株，其中P1是一株可过量分泌胞外蛋白酶的虫生真菌——球孢白僵菌（Beauveria bassiana）；相较于P1，P2的胞外蛋白酶分泌能力更强。该突变株中主要表达的丝氨酸蛋白酶（serine protease）SBP在转录水平上显著上调。研究人员在实验室条件下评估了P1与P2菌株对番茄潜叶蛾（Tuta absoluta）幼虫的杀虫活性，结果显示两种菌株均具备杀虫活性，但P2的杀虫效果显著优于P1。P2的半数致死浓度（median lethal concentration, LC50）较P1低26倍；当使用浓度为1×10^5个分生孢子（conidia）/mL的菌液时，P1与P2的半数致死时间（median lethal time, LT50）分别为4.38天与0.84天。酶学分析结果显示，两株真菌的胞外酶表达模式存在显著差异，尤以蛋白酶与几丁质酶（chitinase）为突出。二维凝胶电泳（two-dimensional gel electrophoresis）结合质谱（mass spectrometry）分析证实，P2菌株中蛋白酶与几丁质酶的表达量显著上调，并进一步揭示了多种蛋白酶同工型的过量表达。本研究揭示了真菌酶学特征与昆虫致病力之间的直接关联，为球孢白僵菌的杀虫潜能提供了分子层面的解释。