The Role Of Calcium In Kidney Bean Defensive Responses Induced By Western Flower Thrip Feeding

Herbivore-induced plant defense responses are important parts of interaction mechanism between insect and host plant, and more and more researchers have been trying to find the idea of insect-resistance from resistant mechanism of plant itself with the plant resistance. Western flower thrips, one of the most important agricultural pests in the world, has caused heavy loss of agricultural production to the world as the characteristics of its feeding, ovipositiondamage and virus transmission. Thrips-bean was choosen as interaction system in this research to detect the dynamic changes of content of key signaling molecule?jasmonic acid and salicylic acid? and the activities of key defense enzymes?lipoxygenase, allene oxide synthase, phenylalnine ammonialyase and ?-1,3-glucanase? and the transcripts level of key defense genes?genes for lipoxygenase, allene oxide synthase, phenylalnine ammonialyase and ?-1,3-glucanase? of jasmonic acid and salicylic acid-signalling pathways under pressure of thrip-feeding at biochemical?using plant endogenous hormone content and enzymes assay? and molecular?using RT-PCR and RT-q PCR of plant defense genes? levels respectively with the using of spraying calcium and Ca²⁺ inhibitors?EGTA and La Cl₃?. Finally, we confirmed the defense response mechanism of two kinds of signaling transductive pathways in kidney bean elicited by thrip-feeding and the role of Ca²⁺ in the process. The results were as follows: 1.The role of calcium in the process of plant defense enzymes activities induced by thrips feeding on Phaseolus vulgaris L. leaf.This experiment determined 4 kinds of defense enzyme activity in signal transduction pathway induced by thrips-feeding and other treatments through using kinetics of enzyme-catalyzed reactions. The results showed that no matter what defense enzyme activity being determined, every treatment group had significant differences in the duration of test period?P<0.05?,while the time point of the highest enzyme's activity were different among all defense enzymes respectively, and significant differences occured in all treatment groups at the same time point: LOX, 6th hr; AOS, 24 th hr; PAL, 0 hr; PR-2, 6th hr. During the peak period as mentioned above, the enzyme activity of thrips feeding and Ca Cl₂ spraying were both higher than control group, thrips feeding with Ca²⁺ spraying was higher than thrips feeding only, while leaves of thrips feeding with inhibitors spraying was lower than thrips feeding only, and no significant difference between two inhibitors treatments[EGTA and La Cl₃?La3+?]?P>0.05?. Moreover, the activity of LOX and PR-2 had another peak after Ca Cl₂ spraying only, they were 3rd hr and 24 th hr. 2.The role of calcium in the process of plant defense genes expression induced by thrips feeding on Phaseolus vulgaris L. leaf.This experiment has determined the expression quantity of key defensive genes in signal transduction pathway by using real-time quantitative PCR?RT-q PCR?. The results showed that LOX gene was the first one reach the expressive peak among defensive genes, at sixth hr after thrips-feeding, and AOS get its first expressive peak value at 12 th hr, and the next expressive peak of LOX & AOS gene are both at 48 th hr. While the increase of expression quantity of both PAL and PR-2, belonging to SA signaling pathway, by contrast, lagged behind LOX expression, and the first expressive peak of both gene were at 12 th hr, then the expression quantity of PAL gene was in the declining trend, and PR-2 gene reach the second peak was at 48 th hr. Besides, the expression quantity of four kinds of defensive genes, which induced by thrips-feeding, could be greatly promoted by spraying Ca CL2, while both EGTA and La Cl₃, two kinds of Ca²⁺ inhibitors, could inhibit the inductive effects induced by thrips-feeding, and two inhibitors had same inhibition effect at the same concentration in this test. 3.The role of calcium in the process of plant endogenous JA/SA induced by thrips feeding on Phaseolus vulgaris L. leaf.This test determined the contents of endogenous JA and SA in common beans by using gas chromatography?GC?. The results showed that the contents of endogenous JA and SA in untreated bean leaf presented obvious changes over the whole treatment period. Compared with healthy control, endogenous JA rapidly accumulated within 1h after thrips-feeding, then falling slowly, and the second drastically increased in JA level measured at 24 h, then decreased. By contrast, the increase of endogenous SA content lagged behind JA burst after thrips-feeding, and had two peaks at 6h and 48 h respectively. The contents of endogenous JA/SA, which induced by thrips-feeding, could be greatly promoted by spraying Ca²⁺, also could be boosted slightly by Ca CL2 application only. In addition, both EGTA and La3+ could inhibit the inductive effects induced by thrips-feeding, and two inhibitors had same inhibition effect at the same concentration in most of the time.