Physiological and molecular bases of inflorescence phototropism in Arabidopsis.

SERRANO A.M, VANDENBUSSCHEF, ; GIORDANO C.V, MALDONADO M.B,; VAN DER STRAETEN D, BOCCALANDRO H.E; BALLARÉ C. ARANA M.V

Foz do Iguazu

Congreso; 11th International Congress of Plant Molecular Biology; 2015

The Brazilian Genetics Society & Genetics and Molecular Biology

Plants are able to orient their structures towards light gradients, and thisresponse is called phototropism. While phototropic responses ofvegetative tissues have been extensively studied, mechanismsunderlying inflorescence bending towards light are still unclear. Thephototropin family of photoreceptors (PHOT1 and PHOT2) is known toinduce the phototropism of inflorescences under artificial light gradients.However, we lack information about the mechanisms underlying thisresponse to natural light gradients, a behavior of potential ecologicalrelevance.Through factorial field experiments using four genotypes (WT,phot1phot2, phot1phot2amiRuvr8 and uvr8) with a combination of filtersthat include/exclude UV or blue light we show that inflorescencephototropism towards sunlight is triggered by wavelengths < 500 nm,and that blue light, perceived by PHOT1 and PHOT2 in combination withUV-B perceived by the photoreceptor UVR8, are involved in thisresponse.In addition, UV-B triggers inflorescence phototropism under controlledconditions through UVR8. At these wavelengths (UV-B), UVR8 appearsmore important than phototropins. The response involves the differentialaccumulation of HY5 at the illuminated side of the bolting stem,suggesting that the effect of UV-B in inflorescence bending might involvethe action of HY5.