| The rice water weevil (RWW), Lissorhoptrus oryzophilusKuschel (Coleoptera: Curculionidae), is a serious pest species both in its original geographical distribution region, i.e., northern America, and its invaded eastern Asia and southern Europe. The weevils have to overcome lots of adverse factors such as locating food, thermal stress and secondary metabolies of the host plant. Its polyphagy implies that olfactory would play an important role in various odor distinguishing; heat shock proteins may involved in the adaptation of thermal stress and detoxification enzymes can metabolize the secondary metabolize that the host plants produced. Nevertheless, all these proteins of the weevils have not been characterized and investigated. New sequence technology promotes our research. We searched the adaptability related genes from the transcriptome and carried out a series of assay of adaptation-related gene expression profiles under different stresses.(1)In the present study, ten OBP genes and five CSP genes of L. oryzophilus were identified from the transcriptome and verified by reverse transcription-polymerase chain reaction (RT-PCR). The expression patterns of these chemosensory genes with respect to tissue distribution were further investigated by quantitative real-time PCR (qRT-PCR). The results indicate that the expression of these genes had tissue specificity. LoOBP8was specifically expressed in antennae, while LoOBP2and LoCSP6were detectable in all tissues, LoOBPl and LoOBP11were relatively highly expressed in antennae and legs, whileLoCSP10was found in relatively high expression in abdomen. OBPs expression varied under different starvation treatment. Three antenna-enriched OBPs (LoOBP1, LoOBP8and LoOBP11), were up-regulated at the first day and reached a peak at the3rd day, but down-regulated afterward. Their similar regulation trends, in consistent with their similar predicted3D structure, imply their similar functions responsing to nutritional stress. However, antennae removed weevils still could locate their rice host plant in the six-arm olfactometer. But when the weevils were put in darkness, numbers of weevils can locate host plant were significantly decreased indicating visual plays important role in weevil’s host locating.(2) We analyzed the composition and expression profiles of Hsp families under sub-lethal temperatures of0℃and43℃, using the quantitative real-time polymerase chain reaction. Eight genes coding Hsp90, Hsp70, and small Hsps were up-regulated under heat stress, while only1Hsp70gene and1Hsp90gene were up-regulated under cold stress. Results indicate that Hsps from all families except Hsp60are responsible for the capacity of L. oiyzophilus to tolerate temperature stress though more genes were up-regulated, and more rapidly, under heat stress than under cold stress. A second study compared Hsp expression patterns in diapausing and non-diapausing female adults and found that the weevils in diapause up-regulated no Hsp gene but down-regulated4small Hsps,2Hsp90,1Hsp70and1Hsp60genes.(3)We identified14glutathione S-transferase(GSTs), of which2belong to Delta,5to Epsilon,2to Omega,1to Sigma,1to Theta,1to Microsomal and1to Unclassified family. We also identified23cytochrome P450monooxygenase(P450s) and23carboxylesterases(COEs). In order to investigate the functions of these detoxification related genes on RWW defencing plant secondary metabolits, we used different host species to feed the weevils. Relative expression levels of these genes were tested with quantitative real-time PCR, the result showed that:only1GST was up-regulated after feeding different host species while8P450s and10COEs were up-regulated after feeding. This suggested that P450s and COEs play more important roles in RWW metabolizing plant secondary metabolites than GST. |
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