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) 是一组具有替代合成化学农药潜力的微生物。然而，EPF的毒力往往不足，因此EPF生物农药的采用相对有限。以往的研究表明，草食动物诱导的植物挥发物（HIPVs）促进了蜡蚧的毒力，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，我们提出了HIPVs通过诱导胞外蛋白酶或/和几丁质酶活性来促进蜡蚧毒力的假设。用不同数量/密度的烟粉虱诱导的番茄 HIPV 处理Lecanicillium lecanii，分析了 HIPV 对蜡蚧毒力和毒力相关酶（细胞外蛋白酶和几丁质酶）活性的影响。通过测量在HIPV 影响下毒力相关酶的Pr1和Chit II基因表达的变化，证实了酶活性的变化。最后，分析毒力与毒力相关酶或基因的相关性，探讨促进蜡螟毒力增强中HIPVs的机制。结果表明，50 只烟粉虱成虫（50-HIPV）诱导番茄植株产生的挥发物显着增强了蜡螟的毒力。当同时暴露于 50-HIPV 和L. lecanii，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显着提高了几丁质酶的活性和Chit II基因的相对表达量，分别增加了62.74%和48.55%。但各组HIPVs对胞外蛋白酶和Pr1基因表达均无促进作用。相关分析结果表明，蜡螟的毒力与几丁质酶的活性和Chit II基因的相对表达显着相关。因此，HIPVs 诱导了L. lecanii 的毒力通过增加几丁质酶活性。本研究展示了增强蜡蚧毒力的重要方法。此外，从化学生态学的角度，研究结果为EPF的现场应用提供了理论支持，也从生化角度揭示了HIPVs对EPF的影响。