Function of BBX proteins under shade.

BOTTO JF

Cordoba

Congreso; 16th International Congress on Photobiology.; 2014

International Union of Photobiology

When plants grow at high densities perceive the early presence of neighboring plants by sensing changes in light quality that surrounds them. This response is primarily mediated by phytochromes, a family of photoreceptors that detect a reduction in the red:far-red ratio  and trigger the shade avoidance syndrome (SAS). The SAS is a group of physiological responses being the most prominent the elongation of vegetative structures that enables plants to anticipate and avoid competition for light in dense stands. We found a group of zinc-finger transcription factors, called B-Box (BBX) proteins, involved in the SAS. Some BBX proteins, that contain two B-Box motifs, play opposite functions under shade. BBX21 positively regulates the expression of early shade-response genes such as PAR1, HFR1, PIL1, and ATHB2, but later it inhibits the elongation growth. These results suggest that BBX21 could be a component of a negative feedback loop to avoid exaggerated elongation responses like that occurring with HFR1 and PAR1. In opposition to BBX21, BBX24 promotes cell elongation under shade. Both BBX proteins act in the COP1 signaling pathway and other BBX proteins can play redundant functions.  This talk will present new evidences for the roles of BBX proteins in the shade signaling pathways.