Two redundant blue-light receptors, known as phototropins （phot1 and phot2）, influence a variety of physiological responses, including phototropism, chloroplast positioning, and stomatal opening in Arabidopsis thali...Two redundant blue-light receptors, known as phototropins （phot1 and phot2）, influence a variety of physiological responses, including phototropism, chloroplast positioning, and stomatal opening in Arabidopsis thaliana. Whereas photl functions in both low- and high-intensity blue light （HBL）, phot2 functions primarily in HBL. Here, we aimed to elucidate phot2-specific functions by screening for HBL- insensitive mutants among mutagenized Arabidopsis photl mutants. One of the resulting phot2 signaling associated （p2sa） double mutants, phot1 p2sa2, exhibited phototropic defects that could be restored by constitutively expressing NON-PHOTOTROPIC HYPOCOTYL 3 （NPH3）, indicating that P2SA2 was allelic to NPH3. It was observed that NPH3-GFP signal mainly localized to and clustered on the plasma membrane in darkness. This NPH3 clustering on the plasmamembrane was not affected by mutations in genes encoding proteins that interact with N PH3, including PHOT11, PHOT2 and ROOTPHOTOTROPISM 2 （RPT2）. However, the HBL irradiation- mediated release of NPH3 proteins into the cytoplasm was inhibited in photl mutants and enhanced in phot2 and rpt2-2 mutants. Furthermore, HBL-induced hypocotyl phototropism was enhanced in photl mutants and inhibited in the phot2 and rpt2-2 mutants. Our findings indicate that photl regulates the dissociation of NPH3 from the plasma membrane, whereas phot2 mediates the stabilization and relocation of NPH3 to the plasma membrane to acclimate to HBL.展开更多
基金supported by the National Natural Science Foundation of China (31670289 and 31570294 to XZ)the National Key Research and Development Program of China (2016YFD0101900)
文摘Two redundant blue-light receptors, known as phototropins （phot1 and phot2）, influence a variety of physiological responses, including phototropism, chloroplast positioning, and stomatal opening in Arabidopsis thaliana. Whereas photl functions in both low- and high-intensity blue light （HBL）, phot2 functions primarily in HBL. Here, we aimed to elucidate phot2-specific functions by screening for HBL- insensitive mutants among mutagenized Arabidopsis photl mutants. One of the resulting phot2 signaling associated （p2sa） double mutants, phot1 p2sa2, exhibited phototropic defects that could be restored by constitutively expressing NON-PHOTOTROPIC HYPOCOTYL 3 （NPH3）, indicating that P2SA2 was allelic to NPH3. It was observed that NPH3-GFP signal mainly localized to and clustered on the plasma membrane in darkness. This NPH3 clustering on the plasmamembrane was not affected by mutations in genes encoding proteins that interact with N PH3, including PHOT11, PHOT2 and ROOTPHOTOTROPISM 2 （RPT2）. However, the HBL irradiation- mediated release of NPH3 proteins into the cytoplasm was inhibited in photl mutants and enhanced in phot2 and rpt2-2 mutants. Furthermore, HBL-induced hypocotyl phototropism was enhanced in photl mutants and inhibited in the phot2 and rpt2-2 mutants. Our findings indicate that photl regulates the dissociation of NPH3 from the plasma membrane, whereas phot2 mediates the stabilization and relocation of NPH3 to the plasma membrane to acclimate to HBL.
