Regulation Of Salt And Drought Stress Responses By SDR In Arabidopsis And Identification Of Proteins Interacting With SDR

The ubiquitin/26S proteasome pathway is very important for protein degradation in plants.The specificity of ubiquitination is often controlled by ubiquitin-protein ligases(or E3s),which facilitate the transfer of ubiquitin to appropriate targets.F-box protein is one subunit of the E3 ligases SCF(Skpl-Cullin/CDC53-F-box).It has been reported that F-box protein is not only related to plant growth,but also to abiotic stress.In this study,we identified the function of a putative F-box protein At5g15710(here named as Salt and Drought Response,SDR).First,a variety of stress responsive elements including ABA-responsive elements,heat shock-responsive elements,dehydration-responsive elements,pathogen and salt responsive elements,dehydration and cold responsive elements were identified in the promoter of SDR by bioinformatics.Second,qRT-PCR analyses showed that the expression of SDR is induced by ABA,heat-shock and salt,while repressed by drought.SDR is expressed in all developmental stage,but higher in rosette leaf and flower.In order to further identify the function of SDR,we cloned SDR from Arabidopsis cDNA library.Both 35S::SDR and 35S::AntiSDR antisense vectors were constructed and transformed into Arabidopsis.SDR fused to eGFP vector was also constructed to locate the protein in subcellular.Data shows that SDR is located in the nucleus through transient expression in onion epidermis cell.35S::SDR is insensitive to salt stress,with regards to the arrested seed germination and post-germination growth,while 35S::AntiSDR is sensitive to salt stress.In addition,35S::SDR is sensitive to drought stress,whereas 35S::AntiSDR is drought tolerant.Futhermore,salt and drought stress-related genes are altered in 35S::SDR plants.HKT1,RD29A,COR15B,KIN1 is down-regulated,while P5CS1 is up-regulated.The above results indicate that SDR is involved in salt and drought stress response in Arabidopsis.For better understanding the function of SDR,this study also used yeast two-hybrid approach to identfy downstream target proteins of SDR.Identified by screening a yeast-covering after the experiment,eight candidate proteins(VAB3,IPMI2,IPMI SSU1,FVE/ACG1,CCoAOMT1,MORF,cytochrome C oxidase and AT3G10270)were obtained.Among 34 positive clones,eleven were characterized as the same protein CCoAOMT1.However,it is unclear for its target proteins yet.Subsequent experiment is under the way.