The AT-hook-containing proteins SOB3/AHL29 and ESC/AHL27 are negative modulators of hypocotyl growth in Arabidopsis.
SOB3, which encodes a plant-specific AT-hook motif containing protein, was identified from an activation-tagging screen for suppressors of the long-hypocotyl phenotype of a weak phyB allele, phyB-4. sob3-D (suppressor of phyB-4#3 dominant) overexpressing seedlings have shorter hypocotyls, and as adults develop larger flowers and leaves, and are delayed in senescence compared with wild-type plants. At the nucleotide level, SOB3 is closely related to ESCAROLA (ESC), which was identified in an independent activation-tagging screen. ESC overexpression also suppresses the phyB-4 long-hypocotyl phenotype, and confers an adult morphology similar to sob3-D, suggesting similar functions. Analysis of transgenic plants harboring SOB3:SOB3-GUS or ESC:ESC-GUS translational fusions, driven by their endogenous promoter regions, showed GUS activity in the hypocotyl and vasculature tissue in light- and dark-grown seedlings. A loss-of-function SOB3 allele (sob3-4) was generated through an ethyl methanesulfonate intragenic suppressor screen of sob3-D phyB-4 plants, and this allele was combined with a predicted null allele, disrupting ESC (esc-8), to examine potential genetic interactions. The sob3-4 esc-8 double mutant had a long hypocotyl in multiple fluence rates of continuous white, far-red, red and blue light. sob3-4 esc-8 phyB-9 and sob3-4 esc-8 cry-103 triple mutants also had longer hypocotyls than photoreceptor single mutants. In contrast, the sob3-4 esc-8 phyA-211 triple mutant was the same length as phyA-211 single mutants. Taken together, these data indicate that SOB3 and ESC act redundantly to modulate hypocotyl growth inhibition in response to light.
Street
Ian H
IH
Department of Biology, Washington University, St. Louis, MO 63130, USA.
Shah
Purvi K
PK
Smith
Alison M
AM
Avery
Nathan
N
Neff
Michael M
MM
D000483:Alleles; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D049108:Cell Enlargement; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D018546:Hypocotyl / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D005810:Multigene Family; D016254:Mutagenesis, Insertional; D009154:Mutation; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics; D030821:Plants, Genetically Modified
D029681:Arabidopsis Proteins; D004268:DNA-Binding Proteins; C528619:ESC protein, Arabidopsis; D045322:Photosynthetic Reaction Center Complex Proteins; C528618:SOB3 protein, Arabidopsis