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Salt hypersensitive mutant 9, a nucleolar APUM23 protein, is essential for salt sensitivity in association with the ABA signaling pathway in Arabidopsis.

ABSTRACT: BACKGROUND:Although the nucleolus involves two major functions: pre-rRNA processing and ribosome biogenesis/assembly, increasing evidence indicates that it also plays important roles in response to abiotic stress. However, the possible regulatory mechanisms underlying the nucleolar proteins responsive to abiotic stress are largely unknown. High salinity is one of the major abiotic stresses, which hinders plant growth and productivity. Here, genetic screening approach was used to identify a salt hypersensitive mutant 9 (sahy9) mutant, also known as apum23, in Arabidopsis thaliana. Functional characterization of SAHY9/APUM23 through analyses of gene/protein expression profiles and metabolites was performed to decipher the possible regulatory mechanisms of the nucleolar protein SAHY9/APUM23 in response to salt stress. RESULTS:Seedlings of the sahy9/apum23 mutant displayed postgermination developmental arrest and then became bleached after prolonged culture under various salt stresses. Transcriptomic and proteomic analyses of salt-treated sahy9/apum23 and wild-type seedlings revealed differential expression of genes/proteins that have similar functional categories of biological processes, primarily those involved in cellular and metabolic processes as well as abiotic and biotic stress responses. However, the consistency of differential gene expression at both the transcript and protein levels was low (~?12%), which suggests the involvement of posttranscriptional processing during the salt response. Furthermore, the altered expression of genes and proteins mediated by SAHY9/APUM23 regarding salt sensitivity involves abscisic acid (ABA) biosynthesis and signaling, abiotic stress responses, and ribosome biogenesis-related genes. Importantly, NCED3, ABI2, PP2CA, and major ABA-responsive marker genes, such as RD20 and RD29B, were down-regulated at both the transcript and protein levels in conjunction with lower contents of ABA and changes in the expression of a subset of LEA proteins in sahy9/apum23 mutants under salt stress. Moreover, the salt hypersensitivity of the sahy9/apum23 mutant was largely rescued by the exogenous application of ABA during salt stress. CONCLUSION:Our results revealed that SAHY9/APUM23 regulated the expression of ribosome biogenesis-related genes and proteins, which further affected the ribosome composition and abundance, and potential posttranscriptional regulation. The salt hypersensitivity of sahy9/apum23 is associated with the ABA-mediated signaling pathway and the downstream stress-responsive network of this pathway.

SUBMITTER: Huang KC

PROVIDER: S-EPMC5831739 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature

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Salt hypersensitive mutant 9, a nucleolar APUM23 protein, is essential for salt sensitivity in association with the ABA signaling pathway in Arabidopsis.

Huang Kai-Chau KC Lin Wei-Chih WC Cheng Wan-Hsing WH

BMC plant biology 20180301 1

<h4>Background</h4>Although the nucleolus involves two major functions: pre-rRNA processing and ribosome biogenesis/assembly, increasing evidence indicates that it also plays important roles in response to abiotic stress. However, the possible regulatory mechanisms underlying the nucleolar proteins responsive to abiotic stress are largely unknown. High salinity is one of the major abiotic stresses, which hinders plant growth and productivity. Here, genetic screening approach was used to identify ...[more]

PMID: 29490615

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Project description:Containing both AP2 domain and B3 domain, RAV (Related to ABI3/VP1) transcription factors are involved in diverse functions in higher plants. A total of eight TsRAV genes were isolated from the genome of Thellungiella salsuginea and could be divided into two groups (A- and B-group) based on their sequence similarity. The mRNA abundance of all Thellungiella salsuginea TsRAVs followed a gradual decline during seed germination. In Thellungiella salsuginea seedling, transcripts of TsRAVs in the group A (A-TsRAVs) were gradually and moderately reduced by salt treatment but rapidly and severely repressed by ABA treatment. In comparison, with a barely detectable constitutive expression, the transcriptional level of TsRAVs in the group B (B-TsRAVs) exhibited a moderate induction in cotyledons when confronted with ABA. We then produced the "gain-of-function" transgenic Arabidopsis plants for each TsRAV gene and found that only 35S:A-TsRAVs showed weak growth retardation including reduced root elongation, suggesting their roles in negatively controlling plant growth. Under normal conditions, the germination process of all TsRAVs overexpressing transgenic seeds was inhibited with a stronger effect observed in 35S:A-TsRAVs seeds than in 35S:B-TsRAVs seeds. With the presence of NaCl, seed germination and seedling root elongation of all plants including wild type and 35S:TsRAVs plants were retarded and a more severe inhibition occurred to the 35S:A-TsRAV transgenic plants. ABA treatment only negatively affected the germination rates of 35S:A-TsRAV transgenic seeds but not those of 35S:B-TsRAV transgenic seeds. All 35S:TsRAVs transgenic plants showed a similar degree of reduction in root growth compared with untreated seedlings in the presence of ABA. Furthermore, the cotyledon greening/expansion was more severely inhibited 35S:A-TsRAVs than in 35S:B-TsRAVs seedlings. Upon water deficiency, with a wider opening of stomata, 35S:A-TsRAVs plants experienced a faster transpirational water loss than wild type and 35S:B-TsRAVs lines. Taken together, our results suggest that two groups of TsRAVs perform distinct regulating roles during plant growth and abiotic defense including drought and salt, and A-TsRAVs are more likely than B-TsRAVs to act as negative regulators in the above-mentioned biological processes.

Dataset Information

Salt hypersensitive mutant 9, a nucleolar APUM23 protein, is essential for salt sensitivity in association with the ABA signaling pathway in Arabidopsis.

Publications

Salt hypersensitive mutant 9, a nucleolar APUM23 protein, is essential for salt sensitivity in association with the ABA signaling pathway in Arabidopsis.

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