A B-box zinc finger protein regulates shade avoidance responses

CARLOS D. CROCCO, MARCELO J. YANOVSKY, JAVIER F. BOTTO

Montreal, Canada.

Congreso; Plant Biology 2010; 2010

ASPB (American Society of Plant Biologist)

Plants grown at high densities perceive through the phytochrome system a decrease in the red to far-red ratio (R:FR) of incoming light, as a warming of future competition in plant communities. The selective absorption of red (R) by canopy leaves, and the reflection of far-red (FR) from neighbor plants, triggers morphological responses such as hypocotyl, stem and petiole elongation, reduction of branching and acceleration of flowering, which are known collectively as shade-avoidance syndrome (SAS). The aim of this work is identify new components of the signaling pathways of the SAS screening mutants with long hypocotyls under shade in a T-DNA population of Arabidopsis thaliana. Here we characterize a mutant named lhus for long hypocotyl under shade. lhus seedlings have longer hypocotyls than wild-type (WT) under low R:FR, but not under sunlight or darkness. lhus  phenotype is the result of a mutation affecting a double B-box zinc finger transcription factor. In short-term shade, LHUS acts as positive regulator of SAS genes, such as PAR1, HFR1, PIL1 and ATHB2. In contrast, global expression analysis of WT and lhus  seedlings reveals that a large number of genes involved in hormonal signalling pathways are negatively regulated by LHUS in response to long-term shade, and this observation fits well with the phenotype of lhus plants grown under low R:FR.