Temperature stress resistance function of Universal Stress Protein (USP) in Arabidopsis thaliana
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A Universal stress protein that enhance heat and cold stress resistance in plant Arabidopsis thaliana;
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Universal stress protein (USP) is identified to provide different living organisms with the ability to respond to different environmental stress. Specifically in plants, abiotic stress tolerance is a desirable phenotype. However understanding the physiological function of USP in Arabidopsis thaliana under abiotic stress condition is still unknown. In this study, atusp mutant was treated with different abiotic stress, but among the abiotic stresses only heat and cold stress shows a critical phenotype. So, this study focuses on the physiological and biochemical function of AtUSP under heat and cold stress. Firstly, upon treatment of atusp mutant in heat stress, it shows a very sensitive phenotype compared to wildtype. This physiological function was confirmed in- vitro experiments, as AtUSP is one of the heat stable proteins, this prompted the idea that the protein could have a chaperone activity. In- vitro experiment showed; AtUSP changes its structure from a low molecular weight to a high molecular weight protein and AtUSP act as a protector in preventing protein aggregation under heat stress condition which is a typical characteristic of a molecular chaperone protein. AtUSP multimeric structure is not only regulated by heat shock but also by redox status and it also shows a disulfide reductase activity. On the other hand, upon the treatment of atusp mutant under cold stress condition, atusp mutant is sensitive compared to wildtype assessing the idea that it could have a RNA chaperone activity. In- vitro data reveal that AtUSP complemented cold sensitivity of an Escherichia coli csp quadruple mutant, which is a typical characteristic of a RNA chaperone gene. After knowing the functions of AtUSP, the localization was checked and found out that it was localized in the different compartment of the cell; plasma membrane, nucleus and cytosol. To further confirm the function of AtUSP, constructed overexpression line will explain more of the physiological function of AtUSP. Surprisingly, AtUSP grows bigger compared to wildtype, vector and atusp mutant. Basing all the results gathered, this study suggested that AtUSP have the following function; in heat stress, AtUSP act as molecular chaperone protein, in cold stress, AtUSP act as RNA chaperone protein and AtUSP has something to do with the growth development of the plants under normal condition but it remains to be further investigated the physiological function of AtUSP in growth development of the plants.