Functional Study Of Brassinosteroid And Jasmonic Acid On The Root Development In Arabidopsis

The characteristics of immobility force plants to adapt to the changing external environment by changing their own development and physiological mechanisms.The plasticity of plant root development is an important basis for plants to adapt to specific growth environment,especially various stress environment.The maintenance and differentiation of quiescent centers(QC)are fundamental for plant root development plasticity.Brassinosteroid(BR)and Jasmonic Acid(JA)can promote QC cell division and periclinal division of root apical meristem cells,but how they will collectively participate in regulation is not clear.Therefore,in this paper,we designed a series of experiments to explore this problem.We first analyzed whether BR would participate in the JA-mediated root development.The results showed that BR was involved in JA mediated inhibition of root elongation.By measuring the root length of BR-related mutants treated with JA,found that BR insensitive mutant bri1-116 was weakly sensitive to the effect of JA inhibiting root elongation,suggesting that there may be some crosstalk between BR and JA in regulating root development.In turn,we explored whether BR promotes root apical meristem cells division depends on JA signaling.By comparing the effect of JA treatment on wild-type Col and BR insensitive mutant bri1-116,it was found that JA could increase the division ratio of QC cells in Col,but could not increase the division ratio of QC cells in bri1-116;moreover,the expression of p WOX5::GFP was significantly enhanced in wild-type after JA treatment,while no such promotion effect was observed in bri1-116/pWOX5::GFP,which indicates that JA promotes the division of QC cells depends on the complete BR signaling pathway.Secondly,through the phenotypic analysis of Col and bri1-116 treated with JA,it was found that JA significantly increased periclinal division ratio of root apical meristem cells in Col,but did not in bri1-116;moreover,when pCYCD6;1::GFP was treated with JA,the fluorescence signal of pCYCD6;1::GFP was enhanced in the endodermis,while in bri1-116/pCYCD6;1::GFP,the overexpression of CYCD6;1 could not be induced even if treated with JA,these results suggest that BR plays an important role in JA induced overexpression of CYCD6;1 and promoted pericyclic division of root apical meristem cells.In order to further explore the specific molecular mechanism of how BR and JA will collectively participate in regulating root development,we first found that BZR1 interacted with JAZ10 through yeast two-hybrid experiment,and the interactions both in vitro and in vivo was further confirmed by bimolecular fluorescence complementation and protein pull-down techniques.At the same time,we found that JAZ10 not only inhibits the ability of BZR1 that to bind promoter of the downstream target genes SAUR15 and CYCD6;1,but also lead to the transcription activity of BZR1 was decreased.In this paper,we preliminarily explored whether BR-mediated root development also depended on JA signal.By analyzing the phenotype of QC cell division of wild type and JA signaling deficient mutant myc2-2,we found that treatment with exogenous BL can increase QC cell division ratio of Col and myc2-2,but considering the functional redundancy of MYC2 protein family,further analysis should be carried out by constructing multiple mutants.In addition,in our study,we found that MYC2 interacts with BZR1 both in vitro and in vivo through yeast two-hybridization,bimolecular fluorescence complementation and protein pull-down techniques.