Sm-Like Protein-Mediated RNA Metabolism Is Required for Heat Stress Tolerance in Arabidopsis.

Masanori Okamoto,Maho Tanaka,Taeko Morosawa,Junko Ishida,Tetsuro Toyoda,Motoaki Seki,Yoshiki Mochizuki,Akihiro Matsui,Kei Iida

doi:10.3389/fpls.2016.01079

Abstract

Sm-like proteins play multiple functions in RNA metabolism, which is essential for biological processes such as stress responses in eukaryotes. The Arabidopsis thaliana sad1 mutant has a mutation of sm-like protein 5 (LSM5) and shows impaired drought and salt stress tolerances. The lsm5/sad1 mutant also showed hypersensitivity to heat stress. GFP-fused LSM5/SAD1 was localized in the nucleus under optimal growth conditions. After heat stress treatment, GFP-fused LSM5/SAD1 fluorescence was also observed as small cytoplasmic dots, in addition to nuclear localization. Whole genome transcriptome analysis revealed that many genes in Arabidopsis were drastically changed in response to heat stress. More heat-responsive genes were highly expressed in lsm5/sad1 mutant at both 2 and 6 h after heat stress treatment. Additionally, intron-retained and capped transcripts accumulated in the lsm5/sad1 mutant after heat stress treatment. In this study, we also identified non-Arabidopsis Genome Initiative transcripts that were expressed from unannotated regions. Most of these transcripts were antisense transcripts, and many capped non-AGI transcripts accumulated in the lsm5/sad1 mutant during heat stress treatment. These results indicated that LSM5/SAD1 functions to degrade aberrant transcripts through appropriate mRNA splicing and decapping, and precise RNA metabolic machinery is required for heat stress tolerance.

Highlights

Higher plants are sessile organisms that remain in the same habitat during their life, even if their surrounding environment changes to unfavorable conditions
We conducted comprehensive transcriptome analysis to understand the molecular function of the LSM5/SAD1 protein during heat stress
We observed that unspliced HSFA3 transcripts accumulated in lsm5/sad1, whereas the amount of mature HSFA3 mRNAs in lsm5/sad1 mutant was reduced compared with the wildtype during heat stress treatment

Summary

Introduction

Higher plants are sessile organisms that remain in the same habitat during their life, even if their surrounding environment changes to unfavorable conditions. Plants have complex defense systems against various environmental stresses. Heat stress is one of the major environmental stresses, and the atmospheric temperature can drastically increase depending on daily weather changes. To adapt to high temperatures, plants dynamically regulate the transcription levels of genes related to heat stress. Heat shock transcription factors (HSFs) are induced in response to heat stress and regulate the expression of heat shock proteins (HSPs) and ascorbate peroxidase (APX) (Panchuk et al, 2002; Wang et al, 2004; Kotak et al, 2007). HSPs function as Molecular Characterization of a Plant Sm-Like Protein molecular chaperones to maintain cellular homeostasis under both optimal and adverse growth conditions. It is well known that HSFs, HSP, and APX are responsible for heat stress tolerance

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Results

Conclusion