Effect On Fiber And Ovule Of Cotton Plants Expressing IaaL Gene Driven By Ovule Specific Promoter P_GhASN

Cotton is an important economic crop in the world scale,the first natural fiber crop,as well as the world sixth oil-bearing crop.Because more than 90%value of cotton exists in the textile fiber, and cotton fibre is the most important textile raw material,it holds an important position in the national economy and people’s lives.Cotton textile fiber is the seed’s epidermis coat while the cotton seed are also from the ovule,which means that there is a complex relationship between development of the cotton ovule and fibre.The growth of the fiber depends on nutrients continuously provided by the ovule.Auxin is one of five classical classes phytohormones.It can not only has remarkable effect on the plant growth,but also promotes the development of the elongation of cell,even plays a crucial role in the development of cotton ovule and fiber.Therefore,it is feasible to increase fiber yield and to improve fiber quality by regulating endogenesis auxin content.RNA hybridization results revealed that GhASN-like gene,isolated from cotton ovule and fiber cDNA library,highly expressed in cotton ovule and fiber.The gene promoter is cloned and fused toβ-glucuronidase（GUS） gene,and transformated into cotton.Based on the expression characteristics of GhASN-like gene as well as the relationship between ovule and fiber development, we trigger to express by using the GhASN-like gene promoter to drive Indoleacetic acid-lysine synthase（iaaL） gene,which expressed protein could combine with free IAA to form a un-function complex,regulate the endogenesis free IAA content.The effect on ovule and fiver growth were observed and provided for genetics evidence of function of IAA.The main results as follows: 1.P_GhASN::GUS vector were transformated into cotton by Agrobacterium-mediated,PCR and histochemical analysis results suggested that the promoter is specially expressed in ovule and fiber during the late periods of the cotton fiber elongation and ealier of secondary wall biosynthesis.2.Thirteen transformation cotton plants of P_GhASN::iaaL by antibiotics screening and PCR identified were obtained.According iaaL gene expression level analysis by real-time PCR,five of thirteen transmation plants were identified,and three plants higher expressed.3.The free IAA in 23 dpa ovule and fiber of five expressed iaaL gene plants were extracted and analyzed by LC-MS.Results show,the content of free IAA reduces significantly in ovule and fiber,which agreement well with the expressive profile result.The higher expression,the lower free IAA content.4.Investigation of transgenic cotton phenotype shown the bolls of transmation are smaller than control.The weight of per seed were decreased and the weight of fiber per seed prominently were increased.So the lint percentage increase in the transgenic cotton plants.The fiber length and fiber strength of transgenic plants were decreased,the Micronaire value were increased and the length uniformity were decreased in the transgenic cotton plants.5.The cross section area and the cell wall area of transgenic fiber were increased.Besides, the cross section of transgenic fiber presents a ring-shape,and the degree of cotton maturity is not enough.In a word,iaaL is expressed in cotton drived by P_GhASN promoter could decrease the free IAA content,inhibit fiber elongation,promote secondary wall thickening,and decrease fiber maturity. Above results suggested that the transgenic cotton plants of overexpressiong iaaL gene in ovule and fibre have negative impact on cotton fiber development.