GASA4, a GA-stimulated gene, participates in light signaling in Arabidopsis

Abstract

Gibberellic acid-stimulated transcripts in Arabidopsis ( GASAs) were previously isolated as GA-stimulated transcript 1 from tomato ( GAST1) homologs and induced by GA. Here, we report that GASA4 is differentially regulated by light and affected by photoreceptors and light signaling transducers in Arabidopsis. Interestingly, GASA4 was down-regulated by a far-red (FR) light signaling regulator far-red insensitive 219 ( FIN219) under all light conditions. GASA4 T-DNA inserted mutant seedlings with undetectable GASA4 transcripts exhibited reduced sensitivity to red (R) and FR light, and can be rescued by the ectopic expression of GASA4; the gasa4 mutant also showed enhanced response to exogenous GA under the same conditions. Furthermore, the gasa4 mutant showed up-regulated expression of several key GA metabolism genes such as GA 20-oxidase 1 ( GA20ox1), GA 3-oxidase 1 ( GA3ox1) and GA 2-oxidase 2 ( GA2ox2), and displayed increased expression of vital flowering time genes, including GI, CO, FT, and SOC1, which leads to an early flowering phenotype under long-day conditions as compared to the wild type. Thus, GASA4, negatively regulated by FIN219, may play various roles to regulate hypocotyl elongation and flowering during Arabidopsis development.