Functional Characterization of SMG7 Paralogs in Arabidopsis thaliana.

Claudio Capitao,Karel Riha,Ortrun Mittelsten Scheid,Aneta Wandrolova,Neha Shukla

doi:10.3389/fpls.2018.01602

Abstract

SMG7 proteins are evolutionary conserved across eukaryotes and primarily known for their function in nonsense mediated RNA decay (NMD). In contrast to other NMD factors, SMG7 proteins underwent independent expansions during evolution indicating their propensity to adopt novel functions. Here we characterized SMG7 and SMG7-like (SMG7L) paralogs in Arabidopsis thaliana. SMG7 retained its role in NMD and additionally appears to have acquired another function in meiosis. We inactivated SMG7 by CRISPR/Cas9 mutagenesis and showed that, in contrast to our previous report, SMG7 is not an essential gene in Arabidopsis. Furthermore, our data indicate that the N-terminal phosphoserine-binding domain is required for both NMD and meiosis. Phenotypic analysis of SMG7 and SMG7L double mutants did not indicate any functional redundancy between the two genes, suggesting neofunctionalization of SMG7L. Finally, protein sequence comparison together with a phenotyping of T-DNA insertion mutants identified several conserved regions specific for SMG7 that may underlie its role in NMD and meiosis. This information provides a framework for deciphering the non-canonical functions of SMG7-family proteins.

Highlights

In eukaryotic cells, gene expression is controlled by several surveillance mechanisms that assure accurate and robust production of functional proteins
We investigated the requirements for the 14-3-3 domain in meiosis and the redundancy between SMG7 and SMG7L paralogs
We observed comparable upregulation of two different premature termination codons (PTC) containing transcripts in smg7-1 and smg77, suggesting that nonsense mediated RNA decay (NMD) is impaired to the similar extent in both alleles

Summary

Introduction

Gene expression is controlled by several surveillance mechanisms that assure accurate and robust production of functional proteins. One such control mechanism is nonsense mediated RNA decay (NMD), which degrades aberrant RNAs (He and Jacobson, 2015; LykkeAndersen and Jensen, 2015; Hug et al, 2016; Raxwal and Riha, 2016). The consensus model, based on studies across a range of organisms, suggests that NMD is induced by the premature translation termination at stop codons in the absence of a full complement of canonical translation termination signals (He and Jacobson, 2015; Lykke-Andersen and Jensen, 2015)

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