Study On Molecular Mechanisms Of Arabidpsis New Peptide Hormones Atpepl And Pep Receptor2

Arabidopsis PEP RECEPTOR1and2(AtPEPRl and AtPEPR2), members of the leucine rich repeat receptor like kinase family, bind to a group of AtPROPEP gene-encoded endogenous peptides,AtPeps. In the leaf innate immunity response, AtPEPRl, but not AtPEPR2, plays a significant role. In contrast to the vast amount of study on function of LRR-RLKs in the leaf, only a few address LRR RLK function in the roots.In this study, We cloned AtPEPR2promoter into the binary expression vector pMDC162and got AtPEPR2promoter::GUS. Then using GUS gene tissue-specific expression activity to locate AtPEPRl promoter, we found that AtPEPR2have strong expression in the vascular tissues of roots. The knockout mutants atpepr2showed a moderate but significantly shorter root phenotype. It was reported in our and other studies that synthetic AtPeps strongly inhibited root elongation at nanomolar concentration, To resolve these contradicting phenomena, we hypothesize that the effect of the synthetic AtPepl on the root growth is concentration-dependent, which could promote growth at relative low concentrations, but inhibit at the high concentrations. To test this hypothesis, we examined the effect of AtPepl on root elongation at concentrations ranging from0.01nM to50nM. Unexpectedly, AtPepl still had a significant inhibitory effect even at0.01nM. This implies that biologically-derived and synthetic AtPep1have distinct function. To address the relative contribution of AtPEPR2to the response, we examined the effects of AtPepl treatment on the roots of atpepr2-1mutants expressing the luminescence protein aequorin,we found that atpepr2-1had50%of the response of the WT. It demonstrated that in the AtPepl-evoked transient rise in cytosolic Ca2+AtPEPR2is also required.