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Characterization of Rice Homeobox Genes, OsHOX22 and OsHOX24, and Over-expression of OsHOX24 in Transgenic Arabidopsis Suggest Their Role in Abiotic Stress Response.

Bhattacharjee A, Khurana JP, Jain M - Front Plant Sci (2016)

Bottom Line: The recombinant full-length and truncated homeobox proteins were found to be localized in the nucleus.Many of these genes were found to be involved in transcriptional regulation and various metabolic pathways.Altogether, our results suggest the possible role of OsHOX22/OsHOX24 homeobox proteins as negative regulators in abiotic stress responses.

View Article: PubMed Central - PubMed

Affiliation: National Institute of Plant Genome Research New Delhi, India.

ABSTRACT
Homeobox transcription factors are well known regulators of plant growth and development. In this study, we carried out functional analysis of two candidate stress-responsive HD-ZIP I class homeobox genes from rice, OsHOX22, and OsHOX24. These genes were highly up-regulated under various abiotic stress conditions at different stages of rice development, including seedling, mature and reproductive stages. The transcript levels of these genes were enhanced significantly in the presence of plant hormones, including abscisic acid (ABA), auxin, salicylic acid, and gibberellic acid. The recombinant full-length and truncated homeobox proteins were found to be localized in the nucleus. Electrophoretic mobility shift assay established the binding of these homeobox proteins with specific DNA sequences, AH1 (CAAT(A/T)ATTG) and AH2 (CAAT(C/G)ATTG). Transactivation assays in yeast revealed the transcriptional activation potential of full-length OsHOX22 and OsHOX24 proteins. Homo- and hetero-dimerization capabilities of these proteins have also been demonstrated. Further, we identified putative novel interacting proteins of OsHOX22 and OsHOX24 via yeast-two hybrid analysis. Over-expression of OsHOX24 imparted higher sensitivity to stress hormone, ABA, and abiotic stresses in the transgenic Arabidopsis plants as revealed by various physiological and phenotypic assays. Microarray analysis revealed differential expression of several stress-responsive genes in transgenic lines as compared to wild-type. Many of these genes were found to be involved in transcriptional regulation and various metabolic pathways. Altogether, our results suggest the possible role of OsHOX22/OsHOX24 homeobox proteins as negative regulators in abiotic stress responses.

No MeSH data available.


Related in: MedlinePlus

Differential gene expression in 35S::OsHOX24 transgenic plants.(A,B) Heatmaps representing expression profiles of all the differentially expressed TFs (A) and genes involved in diverse metabolic pathways (B) in the transgenic line as compared to WT are shown. The color scale representing average log signal values is shown at the bottom. (C,D) GO (biological process) enrichment in differentially expressed genes in the transgenics. Significantly enriched GO terms (P-value ≤ 0.05) in biological process category among down-regulated (C) and up-regulated (D) genes are shown. The bar marked with asterisk indicate terms with high statistical significance (∗∗P-value ≤ 0.001).
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Figure 9: Differential gene expression in 35S::OsHOX24 transgenic plants.(A,B) Heatmaps representing expression profiles of all the differentially expressed TFs (A) and genes involved in diverse metabolic pathways (B) in the transgenic line as compared to WT are shown. The color scale representing average log signal values is shown at the bottom. (C,D) GO (biological process) enrichment in differentially expressed genes in the transgenics. Significantly enriched GO terms (P-value ≤ 0.05) in biological process category among down-regulated (C) and up-regulated (D) genes are shown. The bar marked with asterisk indicate terms with high statistical significance (∗∗P-value ≤ 0.001).

Mentions: To examine the effect of OsHOX24 over-expression on global gene expression, HZIP1-2.3 transgenic line (exhibiting relatively higher susceptibility to various abiotic stresses) was chosen for microarray analysis. A total of 292 genes (112 up-regulated and 180 down-regulated) were found to be significantly (at least twofold, P ≤ 0.05) differentially regulated in the transgenic line as compared to WT (Supplementary Figure S8; Supplementary Table S4). About 8% of the differentially expressed genes belonged to TF category (Figure 9A) and many of them were well known to be stress-responsive. In addition, pathway analysis depicted the involvement of differentially expressed genes in diverse metabolic pathways and developmental processes, such as hormone biosynthesis, secondary metabolite biosynthesis, electron carrier biosynthesis, amino acid, and fatty acid degradation pathways (Figure 9B).


Characterization of Rice Homeobox Genes, OsHOX22 and OsHOX24, and Over-expression of OsHOX24 in Transgenic Arabidopsis Suggest Their Role in Abiotic Stress Response.

Bhattacharjee A, Khurana JP, Jain M - Front Plant Sci (2016)

Differential gene expression in 35S::OsHOX24 transgenic plants.(A,B) Heatmaps representing expression profiles of all the differentially expressed TFs (A) and genes involved in diverse metabolic pathways (B) in the transgenic line as compared to WT are shown. The color scale representing average log signal values is shown at the bottom. (C,D) GO (biological process) enrichment in differentially expressed genes in the transgenics. Significantly enriched GO terms (P-value ≤ 0.05) in biological process category among down-regulated (C) and up-regulated (D) genes are shown. The bar marked with asterisk indicate terms with high statistical significance (∗∗P-value ≤ 0.001).
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4862318&req=5

Figure 9: Differential gene expression in 35S::OsHOX24 transgenic plants.(A,B) Heatmaps representing expression profiles of all the differentially expressed TFs (A) and genes involved in diverse metabolic pathways (B) in the transgenic line as compared to WT are shown. The color scale representing average log signal values is shown at the bottom. (C,D) GO (biological process) enrichment in differentially expressed genes in the transgenics. Significantly enriched GO terms (P-value ≤ 0.05) in biological process category among down-regulated (C) and up-regulated (D) genes are shown. The bar marked with asterisk indicate terms with high statistical significance (∗∗P-value ≤ 0.001).
Mentions: To examine the effect of OsHOX24 over-expression on global gene expression, HZIP1-2.3 transgenic line (exhibiting relatively higher susceptibility to various abiotic stresses) was chosen for microarray analysis. A total of 292 genes (112 up-regulated and 180 down-regulated) were found to be significantly (at least twofold, P ≤ 0.05) differentially regulated in the transgenic line as compared to WT (Supplementary Figure S8; Supplementary Table S4). About 8% of the differentially expressed genes belonged to TF category (Figure 9A) and many of them were well known to be stress-responsive. In addition, pathway analysis depicted the involvement of differentially expressed genes in diverse metabolic pathways and developmental processes, such as hormone biosynthesis, secondary metabolite biosynthesis, electron carrier biosynthesis, amino acid, and fatty acid degradation pathways (Figure 9B).

Bottom Line: The recombinant full-length and truncated homeobox proteins were found to be localized in the nucleus.Many of these genes were found to be involved in transcriptional regulation and various metabolic pathways.Altogether, our results suggest the possible role of OsHOX22/OsHOX24 homeobox proteins as negative regulators in abiotic stress responses.

View Article: PubMed Central - PubMed

Affiliation: National Institute of Plant Genome Research New Delhi, India.

ABSTRACT
Homeobox transcription factors are well known regulators of plant growth and development. In this study, we carried out functional analysis of two candidate stress-responsive HD-ZIP I class homeobox genes from rice, OsHOX22, and OsHOX24. These genes were highly up-regulated under various abiotic stress conditions at different stages of rice development, including seedling, mature and reproductive stages. The transcript levels of these genes were enhanced significantly in the presence of plant hormones, including abscisic acid (ABA), auxin, salicylic acid, and gibberellic acid. The recombinant full-length and truncated homeobox proteins were found to be localized in the nucleus. Electrophoretic mobility shift assay established the binding of these homeobox proteins with specific DNA sequences, AH1 (CAAT(A/T)ATTG) and AH2 (CAAT(C/G)ATTG). Transactivation assays in yeast revealed the transcriptional activation potential of full-length OsHOX22 and OsHOX24 proteins. Homo- and hetero-dimerization capabilities of these proteins have also been demonstrated. Further, we identified putative novel interacting proteins of OsHOX22 and OsHOX24 via yeast-two hybrid analysis. Over-expression of OsHOX24 imparted higher sensitivity to stress hormone, ABA, and abiotic stresses in the transgenic Arabidopsis plants as revealed by various physiological and phenotypic assays. Microarray analysis revealed differential expression of several stress-responsive genes in transgenic lines as compared to wild-type. Many of these genes were found to be involved in transcriptional regulation and various metabolic pathways. Altogether, our results suggest the possible role of OsHOX22/OsHOX24 homeobox proteins as negative regulators in abiotic stress responses.

No MeSH data available.


Related in: MedlinePlus