Date Published: July 20, 2017
Publisher: Public Library of Science
Author(s): Ya-Wen Chang, Jing-Yun Chen, Ming-Xing Lu, Yuan Gao, Zi-Hua Tian, Wei-Rong Gong, Chang-Sheng Dong, Yu-Zhou Du, Yulin Gao.
The polyphagous agromyzid fly, Liriomyza trifolii, is a significant and important insect pest of ornamental and vegetable crops worldwide. The adaptation of insects to different environments is facilitated by heat shock proteins (HSPs), which play an important role in acclimation to thermal stress. In this study, we cloned and characterized five HSP-encoding genes of L. trifolii (Lthsp20, Lthsp40, Lthsp60, Lthsp70, and Lthsp90) and monitored their expression under different thermal stresses using real-time quantitative PCR. Pupae of L. trifolii were exposed to 19 different temperatures ranging from -20 to 45°C. The results revealed that Lthsp20, Lthsp40, Lthsp70 and Lthsp90 were significantly upregulated in response to both heat and cold stress, while Lthsp60 was induced only by heat temperatures. The temperatures of the onset (Ton) and maximal (Tmax) expression of the five Lthsps were also determined and compared with published Ton and Tmax values of homologous genes in L. sativae and L. huidobrensis. Although L. trifolii occurs primarily in southern China, it has cold tolerance comparable with the other two Liriomyza species. Based on the heat shock proteins expression patterns, L. trifolii has the capacity to tolerate extreme temperatures and the potential to disseminate to northern regions of China.
Liriomyza trifolii is an economically important invasive insect pest in China . It was initially discovered in Guangdong in 2005  and has since proliferated throughout the southern region of China . Both larvae and adults of L. trifolii can cause damage to crop plants. The larvae mine tunnels in the leaf tissues, and female adults puncture the leaf tissues for oviposition. Both activities can reduce photosynthesis and increase leaf drop, resulting in lower crop quality and yield [4–5]. In recent years, L. trifolii has spread rapidly throughout the country, causing significant damage to various vegetable and horticultural crops [6–8].
Heat shock proteins function in various biological and physiological processes and may be produced in response to temperature, starvation, or disease [33–37]. In this study, we showed that the coding regions of five L. trifolii hsps are highly conserved relative to that in L. huidobrensis and L. sativae. The C-terminal ends of LtHSP90 and LtHSP70 both contain EEVD motifs, which is consistent with their role as molecular chaperones for interaction with other proteins . LtHSP60 also contained C-terminal (GGM)n repeats, which are typical of mitochondrial forms of HSP60 . However, the other Liriomyza HSPs are likely located in the cytosol. LtHSP40 contained a DnaJ domain near the N-terminus, which is consistent with its function in ATPase activity and role as a co-chaperone with HSP70 in multiple processes (e.g. protein folding, trafficking, assembly, and dissociation) [40–41]. The central portion of LtHSP20 contained an α-crystalline domain like other sHSPs, may have essential functions in various processes including diapause and insect immunity [42–43].