Cloning And Expression Analysis Of Nine Genes In Aux/IAA Family In Gossypium Hirsutum L.

As a phytohormone, auxin plays important roles in many aspects of plant growth and developmental processes. These processes including apical dominance, lateral root formation, tropisms and flower formation. Such a large range it can work, mainly because auxin can act as a signal factor and activate a series of downstream signal pathways. So it is very important to study the signal transduction centered on auxin. Aux/IAAs, which, were generally thought to function as auxin response repressors, have been intensively studied on the model plant Arabidopsis and rice, however, a little information was know in cotton.1. Nine genes, which were classified into Aux/IAA family, were cloned by using homology cloning methods, combining with Tail and RACE in Gossypium. All they had the whole or parts of conservative domains of Aux/IAA superfamily and sequence similarities is 14～67% among them at the the amino acid level, so, we designated them GhAuxl～GhAux9; We predicted their signal peptide via signalP process, They all had no typical signal peptide except GhAux8; we forecasted that phosphorylation was one of the main ways of Aux/IAAs protein post-translational modify by NetPhos2.0 process.2. Real-time fluorescent quantitative PCR was be used to analyse expression patterns of nine GhAuxs gene in genetic standard line TM-1 (Gossypium hirsutum L.). In general, except GhAux9, the other eight genes expressed constitutively in different organizations and the organs. The most of the genes had comparative high expression levels in the root,stem and leaf of the cotton seedling. Such as GhAux1,GhAux2,and GhAux3 mainly expressed in vegetative organs, they maybe involved in regulation of vegetative growth; Compared with the other organizations and the organs, the expression levels of GhAux4,GhAux5,GhAux6 and GhAux7 were higher in ovules at 0 days post anthesis (ODPA), they mainly participated in fiber initiation; the expression levels of GhAux8 was decrease after 2DPA and then enhanced in fibers at 23DPA. It might play a important roles in the early stage of fiber development and in the stage of secondary wall thickening; GhAux9 was fiber specific and it could not be detected in root,stem and leaf. Its expression levels were increase from 0 DPA ovules, with the peak in fiber at 10 DPA then decrease, enhanced in 23DPA fiber cells again.3. We used real-time fluorescent quantitative PCR analyse expression patterns of GhAux4,GhAux5,GhAux6 and GhAux7, which maybe be related to fiber initiation, among TM-1,linted-fuzzlessl and lintless-fuzzless mutants. These mutants involved dominant naked seed N1,recessive naked seed n2,Xinxiangxiaoji linted-fuzzless (XinFLM),Xuzhou-142 lintless-fuzzless(XZ142WX),Xinxiangxiaoji lintless-fuzzless(XinWX),SL1-7-1 and MD-17. The results showed that, except GhAux6, the expression levels of GhAux4,GhAux5 and GhAux7 genes in lintless-fuzzless and linted-fuzzlessl mutants were significantly higher than in TM-1 in ovules at ODPA and 1DPA. We concluded that the expression products of GhAux4,GhAux5 and GhAux7 enriced in the mutants which may be related to the mutants have low levesl of IAA in the initial period of fiber development.4. Semi-quantitative RT-PCR was be used to analyse expression patterns of nine GhAuxs genes after the leaves of cotton seedlings were treated with 0.5uM IAA. The expression levels of all the genes showed obviously higher than the untreated ones. GhAuxl and GhAux2 were induced within minutes; Before inducing, the expression levels of GhAux4,GhAux8 and GhAux9 were low or no expression, they all had obviously transcriptions after 2h; The expressive peak of GhAux5 and GhAux9 was 2h, GhAux3,GhAux4,GhAux6 and GhAux7 was 12h, but, GhAuxl was 2h and 12h respectively.5. Using the BC1 mapping population derived from the hybridization between upland cotton standard line TM-1 and the sea-island cotton cultivar Hai7124, GhAux1 and GhAux5 was localized on chromosome A8 and D8 respectively.