1. Phytochrome-interacting factor PIF3 integrates phytochrome B and UV-B signaling pathways to regulate gibberellin- and auxin-dependent growth in cucumber hypocotyls.
- Author
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Zhao J, Bo K, Pan Y, Li Y, Yu D, Li C, Chang J, Wu S, Wang Z, Zhang X, Gu X, and Weng Y
- Subjects
- Phytochrome B metabolism, Hypocotyl, Gibberellins metabolism, Indoleacetic Acids metabolism, Signal Transduction, Light, Mutation, Basic Helix-Loop-Helix Transcription Factors genetics, Basic Helix-Loop-Helix Transcription Factors metabolism, Phytochrome genetics, Phytochrome metabolism, Cucumis sativus metabolism, Arabidopsis metabolism, Arabidopsis Proteins metabolism
- Abstract
In Arabidopsis, the photoreceptors phytochrome B (PhyB) and UV-B resistance 8 (UVR8) mediate light responses that play a major role in regulating photomorphogenic hypocotyl growth, but how they crosstalk to coordinate this process is not well understood. Here we report map-based cloning and functional characterization of an ultraviolet (UV)-B-insensitive, long-hypocotyl mutant, lh1, and a wild-type-like mutant, lh2, in cucumber (Cucumis sativus), which show defective CsPhyB and GA oxidase2 (CsGA20ox-2), a key gibberellic acid (GA) biosynthesis enzyme, respectively. The lh2 mutation was epistatic to lh1 and partly suppressed the long-hypocotyl phenotype in the lh1lh2 double mutant. We identified phytochrome interacting factor (PIF) CsPIF3 as playing a critical role in integrating the red/far-red and UV-B light responses for hypocotyl growth. We show that two modules, CsPhyB-CsPIF3-CsGA20ox-2-DELLA and CsPIF3-auxin response factor 18 (CsARF18), mediate CsPhyB-regulated hypocotyl elongation through GA and auxin pathways, respectively, in which CsPIF3 binds to the G/E-box motifs in the promoters of CsGA20ox-2 and CsARF18 to regulate their expression. We also identified a new physical interaction between CsPIF3 and CsUVR8 mediating CsPhyB-dependent, UV-B-induced hypocotyl growth inhibition. Our work suggests that hypocotyl growth in cucumber involves a complex interplay of multiple photoreceptor- and phytohormone-mediated signaling pathways that show both conservation with and divergence from those in Arabidopsis., (Published by Oxford University Press on behalf of the Society for Experimental Biology 2023.)
- Published
- 2023
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