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Title: SRL1: A NEW LOCUS SPECIFIC TO THE PHYB-SIGNALING PATHWAY IN ARABIDOPSIS

Author
item HUQ, EMANUL - USDA/UCB PGEC
item KANG, YURAH - USDA/UCB PGEC
item HALLIDAY, KAREN - USDA/UCB PGEC
item QIN, MIMMIN - USDA/UCB PGEC
item QUAIL, PETER - USDA/UCB PGEC

Submitted to: Plant Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2000
Publication Date: 8/1/2000
Citation: Huq, E., Kang, Y., Halliday, K., Qin, M., Quail, P.H. 2000. SRL1: a new locus specific to the phyB-signaling pathway in Arabidopsis. Plant Journal 23(4):461-470.

Interpretive Summary: Our goal was to define molecular components linking phytochrome photoreceptors to target genes. A new genetic locus, SRL1, encoding a component specific to the phytochrome B pathway was identified. Molecular cloning of the SRL1 locus will provide a target for future intervention for the generation of agronomically superior crops.

Technical Abstract: As part of an effort to isolate new Arabidopsis mutants specifically defective in responsiveness to red light, we identified srl1 (short hypocotyl in red light) by screening an EMS-mutagenized M2 population derived from a phytochrome B (phyB)-overexpressor line (ABO). The srl1 mutant shows enhanced responsiveness to continuous red but not far-red light, in both wild-type and ABO backgrounds, consistent with involvement in the phyB-signaling pathway but not that of phyA. The hypersensitive phenotype of srl1 is not due to overexpression of endogenous phyA or phyB, and the locus maps to the center of chromosome 2, distinct from any other known photomorphogenic mutants. srl1 seedlings display enhancement of several phyB-mediated responses, including shorter hypocotyls, more expanded cotyledons, shorter petioles and modestly higher levels of CAB gene expression under red light than the wild type. Double mutant analyses show that the hypersensitive phenotype of srl1 is completely phyB-dependent. The data suggest, therefore, that SRL1 may encode a negatively acting component specific to the phyB-signaling pathway.