Department of Biochemical Science and Technology, National Taiwan University, 1 Sec. 4, Roosevelt Road, Taipei, Taiwan.
J Exp Bot. 2010 Jul;61(12):3305-20. doi: 10.1093/jxb/erq162. Epub 2010 Jun 21.
Heptahelical protein 1 (HHP1) is a negative regulator in abscisic acid (ABA) and osmotic signalling in Arabidopsis. The physiological role of HHP1 was further investigated in this study using transgenic and knock-out plants. In HHP1::GUS transgenic mutants, GUS activity was found to be mainly expressed in the roots, vasculature, stomata, hydathodes, adhesion zones, and connection sites between septa and seeds, regions in which the regulation of turgor pressure is crucial. By measuring transpiration rate and stomatal closure, it was shown that the guard cells in the hhp1-1 mutant had a decreased sensitivity to drought and ABA stress compared with the WT or the c-hhp1-1 mutant, a complementation mutant of HHP1 expressing the HHP1 gene. The N-terminal fragment (amino acids 1-96) of HHP1 was found to interact with the transcription factor inducer of CBF expression-1 (ICE1) in yeast two-hybrid and bimolecular fluorescence complementation (BiFC) studies. The hhp1-1 mutant grown in soil showed hypersensitivity to cold stress with limited watering. The expression of two ICE1-regulated genes (CBF3 and MYB15) and several other cold stress-responsive genes (RD29A, KIN1, COR15A, and COR47) was less sensitive to cold stress in the hhp1-1 mutant than in the WT. These data suggest that HHP1 may function in the cross-talk between cold and osmotic signalling.
七螺旋蛋白 1（HHP1）是拟南芥脱落酸（ABA）和渗透信号的负调控因子。本研究利用转基因和敲除植物进一步研究了 HHP1 的生理作用。在 HHP1::GUS 转基因突变体中，GUS 活性主要在根、脉管系统、气孔、水孔、附着区和隔膜与种子之间的连接点表达，这些区域是膨压调节的关键区域。通过测量蒸腾速率和气孔关闭，表明与 WT 或 c-hhp1-1 突变体（表达 HHP1 基因的 HHP1 互补突变体）相比，hhp1-1 突变体中的保卫细胞对干旱和 ABA 胁迫的敏感性降低。酵母双杂交和双分子荧光互补（BiFC）研究表明，HHP1 的 N 端片段（氨基酸 1-96）与转录因子诱导的 CBF 表达-1（ICE1）相互作用。在土壤中生长的 hhp1-1 突变体在浇水有限的情况下对冷胁迫表现出超敏性。与 WT 相比，hhp1-1 突变体中 ICE1 调节的两个基因（CBF3 和 MYB15）和几个其他冷胁迫响应基因（RD29A、KIN1、COR15A 和 COR47）的表达对冷胁迫的敏感性降低。这些数据表明 HHP1 可能在冷和渗透信号的串扰中发挥作用。
