Study On The Function And Application Of ABA8'-hydroxylase Gene

Pre-harvest Sprouting(PHS) of wheat brings big damage to wheat production around the world.It seriously reduces wheat quality and wheat field,with loss more than 10%.So it is a great task for wheat scientists to solve this problem.Pre-harvest Sprouting is a complex trait affected by both genontype and environment But the dominant factor is seed germination ability,which is controlled by genotype.Plant hormones,especially the ABA and GA,play an important role during the seed developing.Generally ABA induces seed dormancy and prevents seed germination whereas GA relieves dormancy and promotes germination.ABA8'-hydroxylase is the key enzyme in the ABA catabolic way.It has been proved in study of arabidopsis and barley that ABA8'-hydroxylase gene expressed between non-dormancy and dormancy seeds differently a lot.The ABA level in dormancy seeds is much higher than that in non-dormancy seeds,and the germination is delayed obviously.This indicated that the gene is responsible for the changes of ABA level during seed germination and it is the key gene affecting the switch from dormancy to germination.In order to study the function of barley ABA8'-hydroxylase gene HvABA8' OH-1 more clearly.A vector containing the AtCYP707A2-promoter and the HvABA8' OH-1 gene was constructed,then transferred it into AtCYP707A2 mutant.As the result,germination rate of the transgenic lines is similar to that of wiltype but much higher than that of mutant,showing that HvABA8' OH-1 gene is the key gene relative to seed germination.Meanwhile AtCYP707A2-promoter and GUS were used to construct an expressing vector to detect where the promoter works.The GUS signals were found in the trichome of rosser and cauline leaf.h was also found in petal. stigma.basal portion of flower and the portion around the flower,which is nearly consistent with the result of BARe(?)P Browser.ABA8-hydroxylase gene is rather conservative among plant species.It might be a new way to control seed germination to use RNAi technology to knockdown the expression levels of HvABA8 OH-1 gene.Embryo-specific promoter from rice, conserve and specific sequences of HvABA8 OH-1 gene were respectively used to construct two RNAi vectors which were transformed into wheat then.After herbicide selection and primary screening by PCR,27 positive transgenic T₁ plants were obtained,with 4.57%transformation rate.Through increasing seed ABA level caused by the silences of wheat homologue genes,it is possible to select wheat new germplasm with longer dormancy and normal germination in T₂ or T₃ population.