| Multidrug and toxic compound extrusion proteins are widely distributed in kingdoms of living organisms.MATEs are responsible for multidrug resistance in both prokaryotes and eukaryotes through the extrusion of xenobiotics and toxic metabolites from cells.MATE type transporters have exceedingly large numbers of orthologs in plants.Arabidopsis thaliana possesses 56 MATE orthologs.Plant MATEs have been genetically identified, characterized and found to be involved in the detoxification of endogenous secondary metabolites and xenobiotics,although their transport mechanism have not been elucidated.By T-DNA knock-out screening,a dtxj was isolated,which encoded a MATE family protein DTXJ.Compare to wild type,the mutant shows early senescence.After treating with jasmonic acid and darkness,it changes to more severe phenotype.We tried to heterologous express DTXJ::GFP fusion protein in Xenopus oocyte.The DTXJ protein is localized in the plasma membrane.This result is similar to our sequence prediction and reveals DTXJ could work as a membrane multidrug transporter.Further,the GUS staining results show that DTXJ is specifically expressed in guard cells,vascular tissues and also appeared in pollen and root at late develop stage.Combining our work resort of DTXJ localization with the previous studies implys that DTXJ could be an important role involving in JAs signal transduction process.To address this hypothesis,we check out transcription level of two important molecular markers,PR1 and PDF1.2,in SA,JA signal transduction.The transcripts of PDF1.2 were detacted in dtxj mutant,after treated with JA,the expression level of both PR1 and PDF1.2 were increased significantly,which suggests DTXJ mutagenesis may accumulate internal JA and induce high level transcript of PDF1.2.However,it remains unknown if DTXJ transport weak organic acid, such as stress hormone or others.Further examination of DTXJ activity will be applied and more strong evidence should be obtained. |
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