Phototropism of Arabidopsis thaliana inflorescences under natural radiation is mediated by photosensory systems alternative to phototropins

SERRANO ALEJANDRO; GIORDANO, CARLA V.; ARANA VERÓNICA

Córdoba

Congreso; 16th International Congress of Photobiology; 2014

International Union of Photobiology

Flower bending towards light, described by phototropism and heliotropism processes have been studied worldwide throught contrasting natural scenarios mainly from ecological perspectives. However, the underlying physiological mechanisms of these responses are still unclear. Tecently, a study conducted under controlled conditions and artificial lught sources demonstrated that, similarly to what occurs in vegetative organs, blue light signalized by the phototropin family of photoreceptors (PHOT1 and POT2) induces phototropism of inflorescences in Arabidopsis thaliana. Our aim was to characterize inflorescence movements in Arabidopsis thaliana under natural radiation, evaluating the relevance of blue light and of phototropins in these responses. We measured inflorescence bending of wild type plants (WT) vs. phot1phot2 doublé mutants (lacking both photoreceptors) during 48 hr under natural radiation. We found that, unlike othjer species studied, WT inflorescences tracked the sun only from the noon to the evening but not in the morning. Unexpectedly, mutants also exhibited inflorescence bending in contrast to what is reported under artificial conditions. We compared the inflorescence bendidn between plants exposed to an array fo acetate filters wich inverted the natural blue light gradient and plants exposed to a neutral filter control treatment. We found that plants under the inverted blue gradient re-directed their inflorescences following  the new gradient, while control plants returned to the original positions after a brief disorientation period. Our results indicate that blue light is the main signal for inflorescence bending. In contrast with blue light phototropism reported for inflorescences under controlled conditions, photosensory systems alternative to photrotropins are mediating this response in natural environments.