Food and Biological Engineering in Zhangzhou Institute of Technology, No. 2 in College Street, Zhangzhou City 363000, China; Fujian Provincial Key Laboratory of Food Microbiology and Enzyme Engineering, Xiamen, Fujian Province 361021, China.
Department of Information Engineering in Zhangzhou Institute of Technology, No. 2 in College Street, Zhangzhou City 363000, China.
J Invertebr Pathol. 2021 Jul;183:107623. doi: 10.1016/j.jip.2021.107623. Epub 2021 May 28.
Entomopathogenic fungi (EPF) are a group of microorganisms that have potential for replacing synthetic chemical pesticides. However, EPF virulence is often insufficient, and therefore adoption of EPF biopesticides has been relatively limited. Previous studies have shown that herbivore-induced plant volatiles (HIPVs) promoted the virulence of Lecanicillium lecanii, and that extracellular proteases and chitinases are important virulence factors of entomopathogenic fungi. We therefore put forward the hypothesis that HIPVs promote L. lecanii virulence by inducing extracellular protease or/and chitinase activity. Lecanicillium lecanii was treated with tomato HIPVs induced by various numbers/densities of Bemisia tabaci, the effect of HIPVs on L. lecanii virulence and activities of virulence-related enzymes (extracellular proteases and chitinases) was analyzed. Changes in enzyme activities were confirmed by measuring the variations in Pr1 and Chit II genes expression of virulence-related enzymes under the influence of HIPVs. Finally, the correlation between virulence and virulence-related enzymes or genes was analyzed to explore the mechanism of promoting HIPVs in L. lecanii virulence enhancement. The results showed that volatiles produced by the tomato plants induced by 50 B. tabaci adults (50-HIPVs) significantly enhanced the virulence of L. lecanii. When exposed to both 50-HIPVs and L. lecanii, the mortality rate of B. tabaci reached 79.0% within 7 days compared to 28.87% in the control group. Additionally, 50-HIPVs significantly promoted the activity of chitinase and the relative expression of Chit II genes, which consequently increased by 62.74% and 48.55%, respectively. However, each group of HIPVs had no promoting effect on extracellular protease and Pr1 gene expression. Correlation analysis results showed that the virulence of L. lecanii is significantly correlated with the activity of chitinase and relative expression of Chit II genes. Thus, HIPVs induced virulence of L. lecanii by increasing chitinase activity. This study demonstrates important methods to enhance the virulence of L. lecanii. Moreover, from the perspective of chemical ecology, the findings provide theoretical support for field application of EPF, and also reveal the impact of HIPVs on EPF from a biochemical perspective.
昆虫病原真菌（EPF）是一类具有替代合成化学农药潜力的微生物。然而，EPF 的毒力通常不足，因此 EPF 生物农药的采用相对有限。先前的研究表明，取食诱导的植物挥发物（HIPVs）促进了蜡蚧轮枝菌的毒力，并且细胞外蛋白酶和几丁质酶是昆虫病原真菌的重要毒力因子。因此，我们提出假设，即 HIPVs 通过诱导细胞外蛋白酶和/或几丁质酶活性来促进蜡蚧轮枝菌的毒力。用不同数量/密度的烟粉虱诱导的番茄 HIPVs 处理蜡蚧轮枝菌，分析 HIPVs 对蜡蚧轮枝菌毒力和与毒力相关的酶（细胞外蛋白酶和几丁质酶）活性的影响。通过测量 HIPVs 影响下与毒力相关的酶的 Pr1 和 Chit II 基因表达的变化来确认酶活性的变化。最后，分析了毒力与与毒力相关的酶或基因之间的相关性，以探讨 HIPVs 促进蜡蚧轮枝菌毒力增强的机制。结果表明，由 50 只烟粉虱成虫诱导的番茄植株产生的挥发物（50-HIPVs）显著增强了蜡蚧轮枝菌的毒力。当暴露于 50-HIPVs 和蜡蚧轮枝菌时，烟粉虱的死亡率在 7 天内达到 79.0%，而对照组为 28.87%。此外，50-HIPVs 显著促进了几丁质酶的活性和 Chit II 基因的相对表达，分别增加了 62.74%和 48.55%。然而，每组 HIPVs 对细胞外蛋白酶和 Pr1 基因表达均没有促进作用。相关性分析结果表明，蜡蚧轮枝菌的毒力与几丁质酶的活性和 Chit II 基因的相对表达显著相关。因此，HIPVs 通过增加几丁质酶的活性来诱导蜡蚧轮枝菌的毒力。本研究为增强蜡蚧轮枝菌的毒力提供了重要方法。此外，从化学生态学的角度来看，这些发现为 EPF 的田间应用提供了理论支持，同时也从生化角度揭示了 HIPVs 对 EPF 的影响。
