Abstract
Bradysia odoriphaga Yang et Zhang damages roots of 30 plant species, resulting in >50% yield loss. Heat stress can not only affect the survival but also affect the expression of heat shock proteins of B. odoriphaga. In this study, two small heat shock protein genes, Hsp21.9 and Hsp22.3, were cloned from B. odoriphaga. The full-length cDNA sequences of BoHsp21.9 and BoHsp22.3 were 749 and 941 bp in length and contained a 588 and 594 bp open reading frame (ORF), encoding a protein of 196 and 198 amino acids with a calculated molecular weight of 21.9 and 22.3 kDa and an isoelectric point of 6.84 and 6.91. Phylogenetic tree analysis showed that BoHsp21.9 and BoHsp22.3 clustered into one branch with flies. qRT-PCR analyses indicated that BoHsp21.9 and BoHsp22.3 were expressed in all tested developmental stages and body segments, especially induced by heat stress. RNAi-mediated silencing of BoHsp21.9 and BoHsp22.3 significantly decreased the survival rate of fourth-instar larvae when exposed to 38 °C. This is the first study on small heat shock proteins in B. odoriphaga, and BoHsp21.9, and BoHsp22.3 play important roles in the molecular mechanism of B. odoriphaga to theromotolerance.