Isolation And Function Analysis Of SAURs、AUX/IAAs Related To Plant Height In Lagerstroemia Indica

Plant height is one of the most important traits,which is directly related to the crop’s yield and ornamental plant’s visual value.As a kind of traditional woody flower,Lagerstroemia indica shapes its’plant architecture quickly and stably.Therefore,it becomes the proper material for the research of molecular mechanism.In the previous study of the team,seven genes differently expressed in the standard and dwarf L.indica were identified.LfiSAUR1,LfiSAUR39,LfiAUX22 were up-regulated in the standard type,while LfiSAUR26,LfiSAUR50,LfiSAUR31,LfiIAA26 were up-regulated in the dwarf type.To preliminarily verify the role of them in the regulation of L.indica plant height,key genes cloning,VIGS system establishment and key genes verification were done in this study.The results were as followed.（1）CDS regions of seven key genes were isolated in standard and dwarf L.indica and there was no difference in the CDS regions between standard and dwarf types.The length of seven key genes is between 300 bp and 800 bp,and all of these genes have a complete open reading frame.The amino acid sequences of LfiSAUR1,LfiSAUR26,LfiSAUR31,LfiSAUR39 and LfiSAUR50 all have an auxin inducible conserved domain.The amino acid sequences of LfiAUX22,LfiIAA26 have an AUX/IAA conserved domain.The genes are highly homologous to Arabidopsis thaliana and Populus tomentosa.（2）To verify the seven candidate genes quickly,Virus-induced gene silencing system was established in the L.indica.Three parameters（leaf/stem/bud）and three OD₆₀₀（0.5/1/2）were optimized to get the best silencing condition.When the p TRV1+p TRV2 bacterial liquid of OD₆₀₀=1 was injected to the leaf of L.indica,the silencing efficiency was 60%;When the p TRV1+p TRV2 bacterial liquid of OD₆₀₀=2 was injected to the L.indica stem,the silencing efficiency was 65%.The white spot first appeared when the bud was dipped in the vacuum environment.However,the silencing efficiency was not optimistic,only 30%.The white trait caused by VIGS lasted for about 2 months.（3）The functions of seven candidate genes were verified using the VIGS system.It was found that when LfiAUX22 was impressed,the internode length were 10%shorter than CK.The cell length of was shorter by 19.4%,and the endogenous IAA content in the stem was obviously lower.The other 6genes showed no obvious effect on the plant height.In our research,LfiAUX22 was a key gene which regulated the plant height of L.indica.by influencing the content of endogenous IAA and the cell expansion in the stem.