Publications of NIPGR Scientists

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Author: search.filters.author.Khurana, Jitendra P.Subject: search.filters.subject.abiotic stress

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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
    (Frontiers Media S.A., 2016) Bhattacharjee, Annapurna; Khurana, Jitendra P.; Jain, Mukesh
    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.
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    Transcript profiling reveals diverse roles of auxin-responsive genes during reproductive development and abiotic stress in rice
    (Wiley-Blackwell, 2009) Jain, Mukesh; Khurana, Jitendra P.
    Auxin influences growth and development in plants by altering gene expression. Many auxin-responsive genes have been characterized in Arabidopsis in detail, but not in crop plants. Earlier, we reported the identification and characterization of the members of the GH3, Aux/IAA and SAUR gene families in rice. In this study, whole genome microarray analysis of auxin-responsive genes in rice was performed, with the aim of gaining some insight into the mechanism of auxin action. A comparison of expression profiles of untreated and auxin-treated rice seedlings identified 315 probe sets representing 298 (225 upregulated and 73 downregulated) unique genes as auxin-responsive. Functional categorization revealed that genes involved in various biological processes, including metabolism, transcription, signal transduction, and transport, are regulated by auxin. The expression profiles of auxin-responsive genes identified in this study and those of the members of the GH3, Aux/IAA, SAUR and ARF gene families were analyzed during various stages of vegetative and reproductive (panicle and seed) development by employing microarray analysis. Many of these genes are, indeed, expressed in a tissue-specific or developmental stage-specific manner, and the expression profiles of some of the representative genes were confirmed by real-time PCR. The differential expression of auxin-responsive genes during various stages of panicle and seed development implies their involvement in diverse developmental processes. Moreover, several auxin-responsive genes were differentially expressed under various abiotic stress conditions, indicating crosstalk between auxin and abiotic stress signaling.