Abstract: In order to investigate the molecular mechanisms of defense responses of kidney bean to feeding of the western flower thrips (WFT), Frankliniella occidentalis (Pergande), the expression of defense enzyme genes (LOX, AOS, PAL and PR-2) in kidney bean leaves induced by WFT feeding, mechanical damage, exogenous methyl salicylate (MeSA), and exogenous jasmonic acid (JA), respectively, were detected by real-time quantitative PCR (RT-qPCR). The results showed that the expression level of lipoxygenase gene (LOX) reached the peak at 24 h after JA induction and at 48 h after mechanical damage, respectively, but was not significantly different from the controls (P>0.05). LOX was hardly expressed after kidney bean leaves were treated by MeSA. The relative expression level of LOX was about 41.9 times as high as that of the control at 24 h after WFT feeding and was significantly higher than that in other three treatments (P<0.05). The allene oxide synthase gene (AOS) was expressed at a relatively lower level in different treatments and was barely expressed in the entire time of MeSA induction. The phenylalanine ammonialyase gene (PAL) was scarcely expressed during the induction of mechanical damage and JA, and reached the maximum, and its expression was 1.9 times as high as that of the control at 24 h after MeSA treatment. The expression level of PAL rose rapidly after WFT feeding, and was about 4.3 times as high as that of the control at 24 h, significantly higher than in other three treatments (P<0.05). The expression of β-1,3-glucanase gene (PR-2) was suppressed during the induction of WFT feeding and JA. The expression level of PR-2 increased at 24 h after mechanical damage and then decreased during the induction. The expression level of PR-2 dramatically increased in 24 h after MeSA induction, and was nearly 6.63 times as high as that of the control, significantly higher than that in other three treatments (P<0.05), but hardly expressed after 48 h. The findings suggest that WFT feeding could induce the SA- and JA-mediated signal transduction pathways and there are crosstalks between them.

Key words:  Frankliniella occidentalis, kidney bean, feeding, defense genes, gene differential expression