Origin And Evolution Of The Aux/IAA Gene Family And Function Prediction And Expression Analysis Of Partial Plants

In plants,Aux/IAA gene can respond to the induction of auxin in a very short time to thus achieve the role of regulating plant growth and development.Aux/IAA genes can play different roles in various species.In this study,we selected a total of 75 genome related data that have been sequenced,including 13 algae and 62 land plants,to systematically analyze their origin and evolution mechanism in the plant kingdom,and predict and analyze the expression profile of some plants to help us understand the evolutionary characteristics of the gene family,and then understand the functional differentiation of the gene family.The results are as follows:(1)No Aux/IAA gene members were found in algae.A total of 1890 Aux/IAA genes were identified in land plants.The average number of Aux/IAA gene members in bryophytes,ferns,gymnosperms,and angiosperms was 7,9,23 and 33,respectively,indicating that the gene family originated in the early stage of terrestrial plant evolution and had been significantly expanded during the evolution of lower plants to higher plant plants.Phylogenetic analysis showed that 1890 members of the Aux/IAA gene family could be divided into eight subfamilies: Group Ⅰ,Group Ⅱ,Group Ⅲ,Group Ⅳ,GroupⅤ,Group Ⅵ,Group Ⅶ and Group Ⅷ.Protein domain and motif analysis indicate that Group V contains domains III and IV,lacking domains I and II,while Group VI,like other subfamilies,contains four complete domains.They first appeared in bryophytes,forming the two oldest lineages of the Aux/IAA gene family.We speculate that Group VI may be formed by recombination of Group V subfamily and other proteins.The study also found that the newly emerged Group VIII subfamily in ferns may have been replicated and evolved from the ancient lineage Group VI subfamily around 390 million years ago.Similarly,during the evolution of ferns into gymnosperms,the Group IV subfamily began to appear,followed by the evolution of the unique subfamilies Group I,Group II,Group III,and Group VII in angiosperms,Finally,Group Ⅲ and Group Ⅳ subfamilies developed into the two largest subfamilies of Aux/IAA gene family in angiosperms.(2)The collinearity analysis of 54 high-quality genome plants shows that WGD and DSD are the main driving forces affecting the gene in the amplification of Aux/IAA family genes,and more Aux/IAA genes are retained after the species experience the whole genome events.By calculating the molecular evolution rate of tandem repeat genes within species,the Ks/Ka ratio is lower than 1,indicating that these genes are influenced by negative purifying selection during evolution.In basic angiosperms,tandem repeat gene pairs are the most conservative,followed by dicotyledonous plants,and monocotyledonous plants are relatively not conservative.(3)Through the prediction and analysis of the promoter cis-acting elements of Aux/IAA gene in one bryophyte,one fern,one gymnosperm and seven angiosperms,it shows that the gene can be largely expressed under the regulation of plant hormones such as auxin to regulate plant growth and development.Compared with lower plants,higher plants have more cis-acting elements in number and types,reflecting that higher plants can better adapt to more complex environments.In addition,through the different species of Aux/IAA gene expression analysis found that the gene in different plant period different tissues are widely expressed,and Group V subfamily expression is very low.On the one hand,it was related to the lack of domain I and II in its protein structure,and on the other hand,it was related to its being the oldest subfamily gene member,Another possibility is that members of this subfamily may only express themselves under specific conditions.