Characterization of a wheat (Triticum aestivum L.) expansin gene, TaEXPB23, involved in the abiotic stress response and phytohormone regulation.

Expansins are proteins that are generally accepted to be key regulators of cell wall extension and plant growth. We examined the expression pattern of TaEXPB23, a wheat (Triticum aestivum L.) expansin gene, under exogenous phytohormone and abiotic stress treatments. In addition, we evaluated its function in the tolerance to salt stress and high temperature (HT) by overexpressing it in transgenic tobacco plants. In subcellular localization assays, TaEXPB23 localized to the cell wall. Expression analysis demonstrated that the transcription pattern of TaEXPB23 corresponded to wheat coleoptile growth. Real-time RT-PCR analysis revealed that TaEXPB23 transcript expression was upregulated by exogenous methyl jasmonate (MeJA) and salt stress, but downregulated by exogenous gibberellins (GA₃), ethylene (ET), indole-3-acetic acid (IAA) and α-naphthlcetic acid (NAA). Overexpression of TaEXPB23 in tobacco (tabacum) conferred tolerance to salt stress by enhancing water retention ability (WRA) and decreasing osmotic potential (OP). However, transgenic plants overexpressing TaEXPB23 did not show any improvement in the tolerance to HT stress. These results suggested that TaEXPB23 is regulated by phytohormones and is involved in the regulation of salt stress tolerance.