GENETIC IDENTIFICATION OF NOVEL NEGATIVE REGULATORS INVOLVED IN THE LIGHT SIGNALING PATHWAYS.

OLIVERIO, K.A.; CREPY, M.A.; PIÑEIRO, M.A.; JARILLO, J.A.

Évora, Portugal.

Congreso; IX Congreso Luso Espanhol de Fisiologia Vegetal – XVI Reunión Nacional de la Sociedad Española de Fisiología Vegetal.; 2005

Light provides not only the radiant energy for photosynthesis but also the informational signals that plants use to adjust their growth and development in response to changes in the environment. Perception of these signals in Arabidopsis is mediated by three different kinds of photoreceptors: phytochromes, cryptochromes and phototropins. Arabidopsis contains two cryptochromes (cry); cry1 is mainly involved in the control of hypocotyl elongation and cry2 participates in the photoperiodic control of flowering time. Light signaling pathways are controlled by both negative and positive components that normally act downstream of the photoreceptors. In order to identify negative regulators in the blue-light signaling pathways, we have performed a screening looking for mutations that suppress the long hypocotyl phenotype caused by the cry1 mutation. On this way, we have isolated two novel recessive mutations, suppressor of hypocotyl elongation1 (suh1) and suh2, that showed short hypocotyls and unfolding cotyledons under blue light with no obvious phenotype in darkness. These mutations not only affect the photomorphogenic responses under blue light but also enhance the inhibition of hypocotyls elongation and cotyledons unfolding under red and far red light treatments. Taken together, these data suggest that SUH1 and SUH2 loci may encode components that act negatively in the light signaling pathways. Both mutations have been delimited by a map-based cloning approach; suh1 was localized to the bottom of the chromosome 4 and suh2 was mapped to the bottom of the chromosome 1. In parallel, we have initiated the search of third site mutations on cry1 cry2 mutant plants, that suppress either the long hypocotyl phenotype under blue light (also named suh mutations) or the delayed flowering time (suf mutations for suppressor of flowering time). Progress in understanding the role of SUH and SUF loci as negative regulators of light signaling pathways will be presented.