The Novel Protein AtOxR Interacts With CSN5B To Play A Role In H₂O₂ Scavenging And Increase AsA Synthesis To Lowers Oxidative Stress In Arabidopsis Thaliana

In plant cells,the steady-state of reactive oxygen species(ROS)and ascorbic acid(AsA)levels play roles in plant defense against to environment stress,therefore,the metabolism of these redox compounds must be accurately and spatiotemporally controlled.ASA has a variety of physiological functions,that Can play a crucial role in the process of growth and response to abiotic stress in plants.currently,Plants have been found a number of ASA biosynthetic pathways,The D-Man/L-Gal pathway,the predominant pathway of AsA biosynthesis,VTC1 is the most important enzyme involved in this pathway.Recent studies have reported that VTC1 interact with CSN5B can affect to the ASA content,at night,CSN5B was shown enhance VTC1 degradation via the 26S proteasome pathway to negatively regulated AsA content in Arabidopsis;But,how CSN5B regulate the change of AsA levels is unknown in the light and a variety of abiotic stresses conditionsIn this study,an unknown function gene AtOxR was isolated from Arabidopsis thaliana.The expression of AtOxR was induced by mutiple abiotic and oxidative stresses,analyzed the phenotype of AtOxR-overexpressing and AtOxR-RNAi transgenic Arabidopsis plants indicate that AtOxR positive regulate the tolerance to mutiple abiotic and oxidative stresses.We then identified AtOxR-interacting proteins by yeast two-hybrid screening of a cDNA library.This screen identified the photomorphogenic factor COP9 signalosome subunit 5B(CSN5B),which interacted with AtOxR by yeast two-hybrid assays,in vitro pull-down assays and bimolecular fluorescence complementation assays.Determination of the AsA level and H2O2 content showed that the AsA and H2O2 level of AtOxR-overexpressing transgenic plants were obviously higher and lower comparable to the WT plants after challenge with NaCl,mannitol,CuCl2,and H2O2 treatment,respectively.According to these data indicated that the AtOxR-CSN5B interacts could be positive regulated the AsA synthesis to enhance the tolerance to mutiple abiotic and oxidative stress.Hence,we proposed that AtOxR interacts with CSN5B repression VTC1 degradation via the 26S proteasome pathway to maintain a higher AsA content,favourable for scavenging excess H2O2 enhanced the AtOxR-overexpressing transgenic plants tolerance to the multiple abiotic stresses.