engleski

Arabidopsis thaliana seryl-tRNA synthetase participates in cellular stress response

Aminoacyl-tRNA synthetases (aaRSs) play a critical role in translation by catalyzing the ligation of their cognate amino acids and tRNAs to establish the genetic code. Beside their canonical role in translation, aaRSs participate in various cellular processes, including response to stress conditions. Research on the role of aaRSs in stress-responses in plants is very scarce. One proteomic investigation showed upregulation of Arabidopsis seryl-tRNA synthetase (SerRS) in the early response of A. thaliana cells to cadmium exposure. To further investigate the role of SerRS in the stress, we examined growth of Arabidopsis transgenic seedlings overexpressing SerRS. We tested different stress media that induce ionic stress, osmotic stress and stress imposed by heavy metals. Influence of the plant hormones, abscisic acid and brassinosteroids, was also investigated. Our results show that transgenic seeds germinate earlier and that in most cases transgenic seedlings grow better on stress media compared to wild type seedlings. This confirms that enhanced expression of SerRS plays a role in the response of plant to various stress conditions. Stress related function of SerRS may be linked to its cellular localization. To determine subcellular destination of the SerRS protein and targeting properties of its basic C-terminus we prepared three fusion constructs: GFP-SerRS, SerRS-GFP and GFP-C terminus. All constructs were transiently transformed into heterologous epidermal onion cells and homologous Arabidopsis leaves protoplasts. GFP fluorescence was examined under confocal microscope. For all constructs cytosolic localization was observed. In addition, some onion cells showed accumulation of full-length GFP-SerRS or SerRS–GFP fusion proteins in the nucleus. In Arabidopsis protoplasts nuclear localization was observed only in the case of full-length GFP-SerRS fusion protein. In both onion cells and Arabidopsis protoplasts SerRS C- terminus did not exhibit targeting properties of nuclear localization signals. Because GFP- localization experiments gave ambiguous results we performed immunoblot analysis of cytosolic and nuclear fraction of Arabidopsis leaves. Western blot analysis performed so far indicates cytosolic localization of Arabidopsis SerRS protein.

aminoacyl-tRNA synthetase; plant; cellular localization; stress response

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