Functional study of a drought-induced transcription factor, At2g20880, in Arabidopsis
Date Issued
2008
Date
2008
Author(s)
Cheng, Mei-Chun
Abstract
Plant growth and productivity are affected by various abiotic stresses such as heat, cold, drought, and high salinity. Exposure to these stresses induces various biochemical and physiological changes in the process of acquiring stress tolerance. Assortments of genes with diverse functions have been described to respond to these stresses at the transcriptional level. According to the microarray data (Kamiya et al., 2002), we have selected a drought-induced gene, At2g20880, which was induced by 24.5 folds after 2h drought treatment, for studying more details in this thesis. This putative transcription factor belongs to an AP2/ERF superfamily and has a highly conserved AP2 domain. Our Northern blot data revealed that At2g20880 was induced by drought stress, salt stress, and osmotic stress, but not by heat stress and cold stress. In addition, At2g20880 was not induced by ABA, ethylene, and methyl jasmonate treatments. It was demonstrated that the At2g20880 protein can bind to both GCC box (-AGCCGCCAC-) and DRE/CRT element (-TACCGACAT-) in the promoter regions of responsive genes by EMSA. Using promoter-GUS assay, we have found that At2g20880 was expressed in roots, stems, and leaves, especially in vascular tissues, but had lower expression levels in flowers and siliques. Subcellular localization study using a fusion protein consisting of the full length of At2g20880 coding region and GFP fusion under the control of 35S promoter revealed that the GFP fluorescence was detected in the cytosol in onion epidermal cells. However, it was also detected in the nuclei of Arabidopsis protoplasts. Stable transgenic lines were also generated to observe its subcellular localization. Our study indicated that At2g20880-GFP was detected in the nuclei only in PEG-treated protoplasts and drought-treated plants. The amino acid sequence analysis by PredictNLS server showed this protein lacks a typical nuclear localization signal, implying that protein-protein interaction is required for nuclear import during drought treatment. Pull-down assay and co-immuno- precipitation assay were also applied to study the interacting proteins with At2g20880. However, no interacting protein was detected so far. Together with our previous gain-of- function study of At2g20880, At2g20880 may have a function only under drought condition and is a positive regulator in ABA-independent dehydration stress response.
Subjects
Arabidopsis
drought-induced
transcription factor
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