ICAR-National Institute for Plant Biotechnology, New Delhi 110 012, India.
Division of Microbiology, ICAR-Indian Agricultural Research Institute, New Delhi 110 012, India.
J Invertebr Pathol. 2021 Jul;183:107562. doi: 10.1016/j.jip.2021.107562. Epub 2021 Feb 27.
Host plays an important role in influencing virulence of a pathogen and efficacy of a biopesticide. The present study was aimed to characterize the possible factors present in Spodoptera litura that influenced pathogenecity of orally ingested S. marcescens strains, differing in their virulence. Fifth instar larvae of S. litura responded differently as challenged by two Serratia marcescens strains, SEN (virulent strain, LC 7.02 10 cfu/ml) and ICC-4 (non-virulent strain, LC 1.19 10 cfu/ml). Considerable increase in activity of lytic enzymes protease and phospholipase was recorded in the gut and hemolymph of larvae fed on diet supplemented with S. marcescens strain ICC-4 as compared to the larvae treated with S. marcescens strain SEN. However, a significant up-regulation of antioxidative enzymes SOD (in foregut and midgut), CAT (in the midgut) and GST (in the foregut and hemolymph) was recorded in larvae fed on diet treated with the virulent S. marcescens strain SEN in comparison to larvae fed on diet treated with the non-virulent S. marcescens strain ICC-4. Activity of defense related enzymes lysozyme and phenoloxidase activity were also higher in the hemolymph of larvae fed with diet treated with S. marcescens strain SEN as compared to hemolymph of S. marcescens strain ICC-4 treated larvae. More number of over-expressed proteins was observed in the gut and hemolymph of S. marcescens strains ICC-4 and SEN treated larvae, respectively. Identification of the selected differentially expressed proteins indicated induction of proteins involved in insect innate immune response (Immunoglobulin I-set domain, Apolipophorin III, leucine rich repeat and Titin) in S. marcescens strain SEN treated larvae. Over-expression of two proteins, actin related protein and mt DNA helicase, were noted in S. marcescens treated larvae with very high levels observed in the non-virulent strain. Up-regulation of homeobox protein was noted only in S. marcescens strain ICC-4 challenged larvae. This study indicated that ingestion of non-virulent S. marcescens strain ICC-4 induced strong immune response in insect gut while there was weak response to the virulent S. marcescens strain SEN which probably resulted in difference in their virulence.
宿主在影响病原体毒力和生物农药功效方面起着重要作用。本研究旨在研究斜纹夜蛾体内可能存在的影响经口摄入的不同毒力的粘质沙雷氏菌菌株致病性的因素。斜纹夜蛾五龄幼虫对两种粘质沙雷氏菌菌株 SEN（毒力菌株，LC7.02×10^6cfu/ml）和 ICC-4（非毒力菌株，LC1.19×10^6cfu/ml）的反应不同。与用粘质沙雷氏菌菌株 SEN 处理的幼虫相比，用粘质沙雷氏菌菌株 ICC-4 处理的幼虫的肠道和血淋巴中的溶酶体蛋白酶和磷脂酶活性显著增加。然而，与用非毒力粘质沙雷氏菌菌株 ICC-4 处理的幼虫相比，用毒力粘质沙雷氏菌菌株 SEN 处理的幼虫的前肠和中肠中的 SOD（超氧化物歧化酶）、CAT（过氧化氢酶）和 GST（谷胱甘肽 S-转移酶）的抗氧化酶显著上调。与用非毒力粘质沙雷氏菌菌株 ICC-4 处理的幼虫相比，用粘质沙雷氏菌菌株 SEN 处理的幼虫的血淋巴中的溶菌酶和酚氧化酶活性也更高。在分别用粘质沙雷氏菌菌株 ICC-4 和 SEN 处理的幼虫的肠道和血淋巴中观察到更多数量的过表达蛋白。鉴定出的选定差异表达蛋白表明，在粘质沙雷氏菌菌株 SEN 处理的幼虫中诱导了参与昆虫先天免疫反应的蛋白（免疫球蛋白 I 集域、载脂蛋白 III、富含亮氨酸重复和肌联蛋白）。在粘质沙雷氏菌处理的幼虫中观察到两种蛋白（肌动蛋白相关蛋白和 mtDNA 解旋酶）的过表达，在非毒力菌株中观察到非常高的水平。仅在粘质沙雷氏菌菌株 ICC-4 挑战的幼虫中观察到同源盒蛋白的上调。本研究表明，摄入非毒力粘质沙雷氏菌菌株 ICC-4 会在昆虫肠道中引起强烈的免疫反应，而对毒力粘质沙雷氏菌菌株 SEN 的反应较弱，这可能导致它们的毒力不同。
