NbJAZ3 Regulates Jasmonate-mediated Multicellular Trichome Initiation In Tobacco By Repressing NbWo Activity

The trichomes are a type of specific structures initiating from the epidermic cells of plant It can protect plant against the various biotic and abiotic stress and produce a large number of valuable secondary metabolites.Thus,It seems greatly important to study the regulatory mechanism of trichome development to increase trichome density The phytohormone of jasmonate(JA)can promote the single-cell trichome initiation in Arabidopsis thaliana.However,whether JA is able to regulate the initiation of multicellular trichome or not and its specific regulation mechanism still remain unknown.Therefore,we take the Nicotiana benthamiana whose trichomes are all multicellular and glandular as the model to conduct the related research,and the results are as follows1.MeJA treatment to tobacco reveals that JA can induce the initiation of multicellular trichomes and represses the growth of tobacco plant2.To clarify its regulatory mechanism,we clone nine JAZ genes of tobacco and find that one of these genes,the NbJAZ3,is able to interact with a transcription factor NbWo and to repress the transcriptional activity of NbWo by yeast-two-hybrid,BiFC,Dual-LUC and GUS activity analysis.The transcription factor of NbWo is a key regulator of multicellular trichome initiation in tobacco3.qRT-PCR and GUS staining of tissue analysis reveal that the expression level of NbJAZ3 in leaf and flower are higher,Moreover,NbJAZ3 expresses at higher level in mature tissues than young tissues.The subcellular localization results show that NbJAZ3 protein distributes in nucleus and cytoplasm/membrane.Compared with the wild type of tobacco,the overexpression lines of NbJAZ3 show significant decrease of multicellular trichome density and increased biomass of tobacco plant.With further statistical analysis,we find that the decrease of trichome density is mainly caused by the decrease of the long-handle trichome density.But the RNAi lines of NbJAZ3 show no significant difference compared to wild type.Besides,qRT-PCR analysis show that the expression of NbCycB2 and NbMIXTA2 which are important genes regulating trichome initiation decreased significantly in NbJAZ3 overexpression linesBased on all results above,we conclude that NbJAZ3 negatively regulate the initiation of multicellular trichome in tobacco and that the regulation role achieves by repressing the transcritional activity of NbWo and the expression of downstream genes of NbWo.This conclusion explain the mechanism of JA promoting multicellular trichome initiation in tobacco to some extent.