The Role Of AtCNGC2 In Jasmonic Acid Signalling

As a stress signal, jasmonic acid (JA) plays an important role in plant growth and development of resistance and defense responses. It may induce the expression of genes which related to stress resistance and increase the resistance of plants when the plant suffered biotic and abiotic stress. In the same time, the concentration of cytoplasmic free calcium ([Ca²⁺]cyt) will rise. JA-induced calcium mobilization is a branch of the JA signaling pathway which is required in JA signaling network. Plant CNGC, as a non-selective ligand-gated cation channel, is an important component of signal transduction cascade system. It transforms signals from cell external into transmembrane cation current and operates its functions. Some research results had shown that JA-induced apoplastic calcium ions inflowed into cell through AtCNGC2, but there was less study on this field in China. It would have important scientific theory significance that study the role of the AtCNGC2 in JA-induced calcium mobilization and analyse the expression of JA response genes JR1.In order to investigate the functions of AtCNGC2 in JA signaling, we used AtCNGC2 mutant dnd1 and wild-type Arabidopsis as materials, and the leaves from two kind Arabidopsis above were treated by the IP3 receptor antagonist heparin, the CaM antagonist W-7, W-5 (a less potent analog of W-7), the Ca²⁺ channel blocker GdCl₃ and the Ca²⁺ channel activator cAMP to study their effects on JA-induced [Ca²⁺]cyt. Simultaneously, the expressions of JA response gene JR1 in two kind of Arabidopsis seedlings treated by GdCl₃ and cAMP. The main results of this paper are described as follows:1) The intracellular calcium fluorescence intensity of dnd1 (AtCNGC2 mutant) leaves was lower than wild-type, and the JA-induced calcium fluorescence intensity in the mutant was lower than WT when stimulated with 100μmol/L JA. The fluorescence intensity of intracellular calcium was inhibited by heparin, while the fluorescence level of [Ca²⁺]cyt increased to the level of the control when the leaves treated by JA after the pretreatment of heparin.2) The intracellular calcium fluorescence intensity in leaf cells could be enhanced by the treatment of W-7 and the stimulation of JA after treated with W-7. But W-5 was found to be incapable of increasing the fluorescence of JA-induced. 3) The intracellular calcium fluorescence of dnd1 leaves enhanced with the increase of GdCl₃ concentration, but the level of JA-induced intracellular calcium fluorescence was unchanged. Pretreated with GdCl₃ both basal fluorescence intensity and JA-induced intracellular calcium fluorescence of WT leaves were increased, GdCl₃ could promote the increase of JA-induced intracellular calcium fluorescence and the fluorescence of JA-induced was in proportion of GdCl₃ concentration.4) After cAMP treated, the intracellular calcium fluorescence intensity of dnd1 leaves did not change significantly, while the calcium fluorescence intensity of WT leaves enhanced with the increase of cAMP concentration.5) GdCl₃ inhibited the expression of JA-induced JR1 gene on WT Arabidopsis, and the inhibition enhanced with the increase of GdCl₃ concentration. While GdCl₃ had no effect on the expression of dnd1 JR1 gene. cAMP had the positive effect on WT JR1 expression, but had no effect on dnd1.