Cloning and Expression Profile of Gibberellin Insensitive Dwarf GID1 Homologous Genes from Cotton

To advance the understanding of gibberellins (GA) functions in cotton (Gossypium hisutum L.) development, especially fiber development, 6 cotton GID1 homologous genes, GhGID1-1 to GhGID1-6 (GenBank accession numbers FJ790125 to FJ790130), were cloned by searching expressed sequence tag (EST) sequences, extending the flanking sequences by Y-shaped adaptor dependent extension (YADE) method, and amplifying the full-length cDNA by 3′ rapid amplification of cDNA ends (RACE). Multiple sequence alignment indicated that the deduced GhGID1-1 to GhGID1-6 proteins shared high sequence identity with GID1s from other species and contained multiple binding sites with GA and DELLA protein, as well as HGG and GXSXG domains conserved in hormone-sensitive lipase (HSL) family. Three amino acid residuals (G169, G196, and R251) related to rice (Oryza sativa L.) GID1 were also conserved in cotton GID1s. In the phylogenetic tree of GhGID1s and GID1 proteins with known functions, GhGID1-1 to GhGID1-6 were clustered together with 3 Arabidopsis GID1 proteins, and distantly related to GID1s from rice and Selaginella moellendorffii. According to the results by quantitative reverse transcription polymerase chain reaction (RT-PCR), the transcripts of GhGID1-1 to GhGID1-6 were detected in roots, hypocotyls, leaves, petals, anthers, ovules, and fibers. GhGID1-1 and GhGID1-2 were expressed mainly in floral organs, and GhGID1-4 was expressed preferentially in fiber and root. Exogenous GA in medium resulted in alteration of gene expression level in the ovules cultivated in vitro, and the expression of GhGID1-1 and GhGID1-2 was obviously inhibited by GA. These results suggested that the 6 GhGID1 homologous genes might encode biologically functional GID1 homologues involved in GA signaling in cotton. GhGID1-1 was predominantly expressed in ovules; its expression level reached the climax at 10 d post anthesis (DPA) and maintained the high level at 14 DPA and 18 DPA. In fibers, GhGID1-4 was the main GID1 homologue expressed, and its highest-level expression occurred at 6 DPA and declined to a very low level at 14 DPA and 18 DPA. This result strongly suggested that these are relatively independent GA signaling systems in ovules and attached fibers.

摘 要作为赤霉素(GA)受体, GID1是其重要的信号传导组分。为研究GA在棉花发育(特别是纤维发育)中的作用, 本文在EST序列的基础上克隆了6个棉花GID1同源基因(GhGID1-1∼6)。多重序列分析表明, 棉花GID1同源蛋白GhGID1-1∼6与拟南芥和水稻的GID1蛋白高度同源, 具有多个与GA和DELLA蛋白的结合位点以及激素敏感酯酶家族保守域HGG和GXSXG。定量RT-PCR分析表明, GhGID1-1∼6基因在棉花不同器官和组织中表达水平有差异, 其中GhGID1-1和GhGID1-2在花器官中高表达, GhGID1-4基因在纤维和根中优势表达。胚珠体外培养基中外加GA使GID1同源基因表达水平发生变化, GhGID1-1和GhGID1-2基因的表达水平明显受GA抑制。比较发现, 在胚珠和纤维中优势表达的GID1同源基因不同, GID1基因表达水平随发育时期变化的趋势也不相同, 表明棉花胚珠和纤维具有相对独立的GA信号识别系统。