Reduced Expression of a Novel Midgut Trypsin Gene Involved in Protoxin Activation Correlates with Cry1Ac Resistance in a Laboratory-Selected Strain of <i>Plutella xylostella</i> (L.)
Lijun Gong,
Shi Kang,
Junlei Zhou,
Dan Sun,
Le Guo,
Jianying Qin,
Liuhong Zhu,
Yang Bai,
Fan Ye,
Mazarin Akami,
Qingjun Wu,
Shaoli Wang,
Baoyun Xu,
Zhongxia Yang,
Alejandra Bravo,
Mario Soberón,
Zhaojiang Guo,
Lizhang Wen,
Youjun Zhang
Affiliations
Lijun Gong
College of Plant Protection, Hunan Agricultural University, Changsha 410125, China
Shi Kang
Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
Junlei Zhou
Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
Dan Sun
Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
Le Guo
College of Plant Protection, Hunan Agricultural University, Changsha 410125, China
Jianying Qin
Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
Liuhong Zhu
Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
Yang Bai
Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
Fan Ye
College of Plant Protection, Hunan Agricultural University, Changsha 410125, China
Mazarin Akami
Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
Qingjun Wu
Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
Shaoli Wang
Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
Baoyun Xu
Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
Zhongxia Yang
College of Plant Protection, Hunan Agricultural University, Changsha 410125, China
Alejandra Bravo
Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca, Morelos 62250, Mexico
Mario Soberón
Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca, Morelos 62250, Mexico
Zhaojiang Guo
Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
Lizhang Wen
College of Plant Protection, Hunan Agricultural University, Changsha 410125, China
Youjun Zhang
Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
Bacillus thuringiensis (Bt) produce diverse insecticidal proteins to kill insect pests. Nevertheless, evolution of resistance to Bt toxins hampers the sustainable use of this technology. Previously, we identified down-regulation of a trypsin-like serine protease gene PxTryp_SPc1 in the midgut transcriptome and RNA-Seq data of a laboratory-selected Cry1Ac-resistant Plutella xylostella strain, SZ-R. We show here that reduced PxTryp_SPc1 expression significantly reduced caseinolytic and trypsin protease activities affecting Cry1Ac protoxin activation, thereby conferring higher resistance to Cry1Ac protoxin than activated toxin in SZ-R strain. Herein, the full-length cDNA sequence of PxTryp_SPc1 gene was cloned, and we found that it was mainly expressed in midgut tissue in all larval instars. Subsequently, we confirmed that the PxTryp_SPc1 gene was significantly decreased in SZ-R larval midgut and was further reduced when selected with high dose of Cry1Ac protoxin. Moreover, down-regulation of the PxTryp_SPc1 gene was genetically linked to resistance to Cry1Ac in the SZ-R strain. Finally, RNAi-mediated silencing of PxTryp_SPc1 gene expression decreased larval susceptibility to Cry1Ac protoxin in the susceptible DBM1Ac-S strain, supporting that low expression of PxTryp_SPc1 gene is involved in Cry1Ac resistance in P. xylostella. These findings contribute to understanding the role of midgut proteases in the mechanisms underlying insect resistance to Bt toxins.
