Transcriptional Downregulation of Rice rpL32 Gene under Abiotic Stress Is Associated with Removal of Transcription Factors within the Promoter Region

Pradipto Mukhopadhyay,Malireddy K Reddy,Sneh Lata Singla-Pareek,Sudhir K Sopory,Steven R Ellis

doi:10.1371/journal.pone.0028058

Pradipto Mukhopadhyay, Malireddy K Reddy + Show 3 more

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https://doi.org/10.1371/journal.pone.0028058

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Abstract

BackgroundThe regulation of ribosomal proteins in plants under stress conditions has not been well studied. Although a few reports have shown stress-specific post-transcriptional and translational mechanisms involved in downregulation of ribosomal proteins yet stress-responsive transcriptional regulation of ribosomal proteins is largely unknown in plants.Methodology/Principal FindingsIn the present work, transcriptional regulation of genes encoding rice 60S ribosomal protein L32 (rpL32) in response to salt stress has been studied. Northern and RT-PCR analyses showed a significant downregulation of rpL32 transcripts under abiotic stress conditions in rice. Of the four rpL32 genes in rice genome, the gene on chromosome 8 (rpL32_8.1) showed a higher degree of stress-responsive downregulation in salt sensitive rice variety than in tolerant one and its expression reverted to its original level upon withdrawal of stress. The nuclear run-on and promoter:reporter assays revealed that the downregulation of this gene is transcriptional and originates within the promoter region. Using in vivo footprinting and electrophoretic mobility shift assay (EMSA), cis-elements in the promoter of rpL32_8.1 showing reduced binding to proteins in shoots of salt stressed rice seedlings were identified.ConclusionsThe present work is one of the few reports on study of stress downregulated genes. The data revealed that rpL32 gene is transcriptionally downregulated under abiotic stress in rice and that this transcriptional downregulation is associated with the removal of transcription factors from specific promoter elements.

Highlights

Plants encounter a number of abiotic stresses which limit agricultural production
The data revealed that ribosomal protein L32 (rpL32) gene is transcriptionally downregulated under abiotic stress in rice and that this transcriptional downregulation is associated with the removal of transcription factors from specific promoter elements
We have studied the transcriptional regulation of genes encoding 60S ribosomal protein rpL32 in rice under salt stress

Summary

Introduction

Plants encounter a number of abiotic stresses which limit agricultural production. Classical breeding programs, as the initial attempts with genetic engineering to raise stress tolerant plants have met with limited success [1]. Not much was known about regulation of expression of genes encoding ribosomal proteins in plants until recently. Pathways of translational downregulation of ribosomal proteins as observed in mammals and transcriptional regulation of ribosomal proteins, somewhat similar to yeast, have been described in plants earlier [12,13,14,15,16,17]. Altered expression of ribosomal proteins under stress has been shown to involve the post-transcriptional and translational regulatory mechanisms, stress-specific transcriptional regulation of ribosomal proteins is still to be reported in plants. The regulation of ribosomal proteins in plants under stress conditions has not been well studied. A few reports have shown stress-specific post-transcriptional and translational mechanisms involved in downregulation of ribosomal proteins yet stress-responsive transcriptional regulation of ribosomal proteins is largely unknown in plants

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