OsGSR1 is involved in crosstalk between gibberellins and brassinosteroids in rice

Abstract

SummaryGibberellins (GAs) and brassinosteroids (BRs), two growth-promoting phytohormones, regulate many common physiological processes. Their interactions at the molecular level remain unclear. Here, we demonstrate that OsGSR1, a member of the GAST (GA-stimulated transcript) gene family, is induced by GA and repressed by BR. RNA interference (RNAi) transgenic rice plants with reduced OsGSR1 expression show phenotypes similar to plants deficient in BR, including short primary roots, erect leaves and reduced fertility. The OsGSR1 RNAi transgenic rice shows a reduced level of endogenous BR, and the dwarf phenotype could be rescued by the application of brassinolide. The yeast two-hybrid assay revealed that OsGSR1 interacts with DIM/DWF1, an enzyme that catalyzes the conversion from 24-methylenecholesterol to campesterol in BR biosynthesis. These results suggest that OsGSR1 activates BR synthesis by directly regulating a BR biosynthetic enzyme at the post-translational level. Furthermore, OsGSR1 RNAi plants show a reduced sensitivity to GA treatment, an increased expression of the GA biosynthetic gene OsGA20ox2, which is feedback inhibited by GA signaling, and an elevated level of endogenous GA: together, these suggest that OsGSR1 is a positive regulator of GA signaling. These results demonstrate that OsGSR1 plays important roles in both BR and GA pathways, and also mediates an interaction between the two signaling pathways.

TheGibberellic Acid Stimulated-LikeGene Family in Maize and Its Role in Lateral Root Development

“…To obtain a more comprehensive overview on monocot GSL genes, the rice genome was also searched for RSI1 homologs as a reference. This led to the identification of six novel gene family members in addition to the previously published genes OsGSR1 (Wang et al, 2009), OsGASR1, and OsGASR2 (Furukawa et al, 2006; Table I). The novel rice genes were numbered according to their closest maize relatives (OsGSL1, OsGSL5, OsGSL7, OsGSL8, and OsGSL9) or in one instance, when no maize ortholog was available, according to the closest Arabidopsis relative (OsGSL12).…”

“…Besides the newly identified maize GASTlike genes ZmGSL1 to ZmGSL10, six novel rice genes were identified, bringing the total number of GASA/ GAST-like members from rice to nine. Phylogenetic reconstructions involving the previously identified rice (Furukawa et al, 2006;Wang et al, 2009), tomato (Shi et al, 1992;Taylor and Scheuring, 1994), and Arabidopsis (Roxrud et al, 2007) full-length GASTlike protein sequences grouped the newly identified monocot members into three distinct phylogenetic clades. The comparison of monocot and dicot GASA/GAST-like proteins in our study therefore reveals that during evolution eudicot members of the GASA/GAST-like family have developed along three different directions.…”

One new kind of phytohormonal signaling integrator: Up-and-coming GASA family genes

“…24 Rice OsGSR1 gene expression is inhibited by GA and induced by BR. 14 And the AtGASA4 and AtGASA6 are ingeneral up regulated by growth hormones (auxin, BR, cytokinin, and GA) and down regulated by stresshormones (ABA, JA, and SA). 40 These results suggesting that the GASA gene family may be involved in a wide range of plant hormone signal transduction network.…”

“…39 Normally, GASA proteins form 5 or 6 disulfide bonds and these disulfide bonds may be necessary for the senior structural of GASA and be critical for the GASA protein interactions with other proteins. 12,18 GASA protein participate in the regulation of plant growth and development upon interacting with different proteins, such as rice OsGSR1 is involved in the regulation of GA and BR crosstalk through interaction with BR (brassinosteroid) synthase DIM / DWF1 protein; 14 Potato Snakin-1 protein can interact with itself to play role in in the regulating cell division of potato leaf (Nahirnak et al, 2012). 32 …”

“…[9][10][11][12][13][14][15] GAST1 (GA-stimulated transcript 1) is the first GASA family gene member has been isolated and identified from tomato (Lycopersicon esculentum). 9 By far a great number of GASA genes and proteins have been isolated and identified from Petunia (Petunia hybrida), Arabidopsis (Arabidopsis thaliana), Potato (Solanum tuberosum) and rice (Oryza sativa) etc.. [13][14][15][16][17][18][19][20][21] GASA proteins play an important role in the regulation of plant growth and development, including participation in seed germination, 22,23 lateral root formation, 24,25 stem elongation, 18,26 flowering, 20,26 flower and fruit development, [27][28][29] biological and abiotic stresses responses, 12,13,[15][16][17]30,31 as well as the hormonal signal transduction. 9,14,15,31 The structure and function of this kind of proteins have a deeper understanding with different GASA members has been identified from a variety of plant species.…”