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Plant Mol Biol. 2007 Nov;65(5):655-65. Epub 2007 Sep 8.

The bHLH-type transcription factor AtAIB positively regulates ABA response in Arabidopsis.

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State Key Laboratory of Plant Genomics, Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, No. 5 Datun Road, Chaoyang District, Beijing 100101, China.


The phytohormone ABA was known to play a vital role in modulating plant responses to drought stress. Here, we report that a nuclear-localized basic helix-loop-helix (bHLH)-type protein, AtAIB, positively regulates ABA response in Arabidopsis. The expression of AtAIB was transitorily induced by ABA and PEG, although its transcripts were accumulated in various organs. We provided evidence showing that AtAIB has transcriptional activation activity in yeast. Knockdown of AtAIB expression caused reduced sensitivity to ABA, whereas overexpression of this gene led to elevated sensitivity to ABA in cotyledon greening and seedling root growth. Furthermore, soil-grown plants overexpressing AtAIB showed increased drought tolerance. Taken together, these results suggested that AtAIB functions as a transcription activator involved in the regulation of ABA signaling in Arabidopsis.

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