engleski

Interplay of proteins involved in translation and steroid hormone metabolism in Arabidopsis

The rules of genetic code are established by aminoacyl-tRNA synthetases (aaRSs), enzymes that covalently link tRNA with its cognate amino acid. Many aaRSs are involved in diverse cellular processes beyond translation by forming protein- protein interactions. However, the studies of plant aaRS assemblies are scarce. Recently, we identified BEN1 as protein interactor of Arabidopsis seryl-tRNA synthetase (SerRS). BEN1 is a putative oxidoreductase involved in metabolism of steroidal plant hormones brassinosteroids. These plant growth-promoting hormones regulate a variety of physiological processes crucial for normal plant growth and development and are also involved in plant stress response. The SerRS:BEN1 complex is the first protein complex of plant aaRSs discovered so far and also one of the rare examples of interaction of aaRSs with enzymes involved in primary or secondary metabolism. To pinpoint regions responsible for interaction, truncated variants of both SerRS and BEN1 were prepared and analyzed using microscale thermophoresis, that enables KD determination. Detailed analysis showed that interaction interface involves SerRS globular catalytic domain and acidic N-terminus of BEN1. Moreover, first 17 amino acids of BEN1 is necessary, but not sufficient for interaction, implying that other parts of BEN1 also participate in interaction with SerRS. Furthermore, using RT-qPCR we observed that expression of BEN1 gene in transgenic plants overexpressing SerRS is slightly lower compared to wild type. To test whether SerRS regulates BEN1 expression in nucleus we determined its localization. Our data show that SerRS is exclusively localized in cytosol, despite its several putative nuclear localization signals. We also investigated the role of SerRS in stress using transgenic plants overexpressing SerRS. Our results show that transgenic seeds germinate earlier and that in most cases transgenic seedlings grow better on various stress media compared to wild type seedlings. This indicates that enhanced expression of SerRS plays a role in the response of Arabidopsis to abiotic stress conditions. Considering that brassinosteroids are also involved in plant stress response we discuss functional importance of SerRS:BEN1 assembly.

aminoacyl-tRNA synthetase ; seryl-tRNA synthetase ; protein-protein interactions ; plant ; brassinosteroids ; localization

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