HHP1, a novel signalling component in the cross-talk between the cold and osmotic signalling pathways in Arabidopsis.
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.
Chen
Chin-Chung
CC
Department of Biochemical Science and Technology, National Taiwan University, 1 Sec. 4, Roosevelt Road, Taipei, Taiwan.
Liang
Ching-Shin
CS
Kao
Ai-Ling
AL
Yang
Chien-Chih
CC
D000040:Abscisic Acid / Q000502:physiology; D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003080:Cold Temperature; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D055786:Gene Knockout Techniques; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009995:Osmosis; D054046:Plant Stomata / Q000502:physiology; D018526:Plant Transpiration; D030821:Plants, Genetically Modified / Q000235:genetics / Q000502:physiology; D018749:RNA, Plant / Q000235:genetics; D015398:Signal Transduction; D013312:Stress, Physiological; D020798:Two-Hybrid System Techniques; D014867:Water / Q000502:physiology
D029681:Arabidopsis Proteins; C541749:HHP1 protein, Arabidopsis; D008565:Membrane Proteins; D018749:RNA, Plant; D014867:Water; D000040:Abscisic Acid