Transcriptomic and proteomic analyses of the immune responses of C-type lectin from Conogethes punctiferalis against fungal infection

Shaohua Li¹Zhiwei Kang^2,3Xiangdong Li^2,4Hai-Lei Wei⁵Xiangchu Yin^2,3Fanghua Liu^2,3*Fangqiang Zheng^1*

• ¹Shandong Agricultural University, Taian, China
• ²Shandong Agricultural University, Tai'an, China
• ³Hebei University, Baoding, China
• ⁴Shandong Academy of Agricultural Sciences, Jinan, China
• ⁵Chinese Academy of Agricultural Sciences, Beijing, China

Introduction: C-type lectins (CTLs), a family of pattern recognition receptors, participate in insect innate immunity and could serve as potential targets for insect pest management. However, information about CTLs in the immune responses of Conogethes punctiferalis, a destructive insect pest damaging to maize in China, has received minimal attention. Methods: The integrative transcriptomic and proteomic analyses of non-infected and Beauveria bassiana-infected C. punctiferalis larvae were performed using RNA-Seq and iTRAQ techniques. The survival rates and phenotypic changes of larvae infected with B. bassiana were investigated using RNA interference (RNAi). Results: Based on the transcriptome and proteome data, screening identified 314 immune-related genes and proteins, including 14 CTLs. According to the number and organization of carbohydrate recognition domains (CRDs), six CTLs were classified as CTL-S (single CRD), while eight CTLs were classified as IML (dual CRD). The expression of a novel CTL, designated CpIML4, increased in response to B. bassiana infection. The developmental stage and larval tissue expression analyses showed that CpIML4 was highly expressed in the 5th-instar larvae and their hemolymph, respectively. RNAi-mediated knockdown of CpIML4 significantly decreased resistance to B. bassiana, as indicated by lower survival rates and pathological phenotypic changes of larval cuticle. The larvae exhibited developmental malformation and black spots on the cuticle, and the dead larvae turned black and wrinkled. Discussion: These results demonstrate that CpIML4 might play a crucial role in the immune responses of C. punctiferalis against B. bassiana infection. Collectively, our findings not only provide a comprehensive view of the immune responses of C. punctiferalis to B. bassiana infection, but also enhance our understanding of C. punctiferalis CTLs and highlight candidate genes for RNAi-mediated insect pest control.