Raphanusanin-induced genes and the characterization of RsCSN3, a raphanusanin-induced gene in etiolated radish hypocotyls

Abstract

Raphanusanin is a light-induced growth inhibitor involved in inhibition of hypocotyl growth in response to unilateral blue light illumination in radish seedlings. To understand better the role of raphanusanin in growth inhibition, we randomly analyzed raphanusanin-induced genes using a modified DD-RT-PCR (differential display RT-PCR) approach. The differential expression RT-PCR approach resulted in identification of four known candidate genes, of which three encoded functional proteins known to be related to responsiveness to diverse environmental stimuli. One of these genes appeared to be an essential element in the inhibition of hypocotyl growth, and was named RsCSN3 (a homologue of subunit 3 of the COP9 signalosome). During the growth inhibition that was observed within minutes of irradiation, the expression of the RsCSN3 gene was increased by phototropic stimulation, as well as by raphanusanin treatment, suggesting that this gene is involved in light-induced growth inhibition. In addition, down-regulation of the RsCSN3 transcript, that is specifically expressed at 60 min after the onset of stimulation under blue light, green light, and raphanusanin treatment, shows a functional correlation with the phototropic response.