Evolution And Function Analysis Of KLU Gene Family In Soybean

Duplication events and a high rate of retention of extant pairs of duplicate genes have contributed to an abundance of duplicate genes in plant genomes,resulting to the production of the most abundant raw materials for genic evolution.Most of the duplicate genes lost their function and were eventually removed.However,once retained via various mechanisms,the duplicates would contribute to the evolution of novel functions,such as the production of floral structures,induction of disease resistance and adaptation to stress.As an ancient tetraploid,Glycine max has undergone several rounds of whole-genome duplications as well as abundant tandem duplication,segmental duplication and transposon.These generated duplicates may produce various mutations randomly.When under different selective pressure,these mutations would accumulate differently,resulting to the divergence of expression patterns and functions.Thus,duplicate genes would be pseudogenized,subfunctionalized and/or neofunctionalized,then make different contribution to the growth and development of soybean,such as grain quality,fruit shape,and flowering time.Therefore,understanding the mechanisms and impacts of gene duplication will be important to the future studies of plants in general and of agronomical significance in particular.In this paper,we surveyed the duplication mechanisms,retention,evolution,expression patterns and functions of three GmCYP78 A subfamily genes.The main research contents are as following:1.Clone and evolution analysis of the GmCYP78 A subfamily genesWe searched out three closest relative genes in soybean genome using the amino acid sequence of KLU in Arabidopsis thaliana,which means that Arabidopsis KLU homologue has three homologous in soybean.Then we cloned GmCYP78A70,GmCYP78A57 and GmCYP78A72.The synteny analysis showed that GmCYP78A70 and GmCYP78A57 were duplicated during the Glycine WGD event,followed the duplication of GmCYP78A72 through a microhomology-mediated BIR(break-induced replication)pathway.2.Expression patterns and functions of the GmCYP78 A subfamily genesIn our observations,clear divergence of expression patterns was found among the GmCYP78 A duplicate genes(Fig 3 and 4).GmCYP78A70 expresses specifically in vegetative meristem,while GmCYP78A57 expresses mainly in floral organ and seed.Moreover,GmCYP78A72 generally expresses in all the tissues above.Expression levels of the three genes increase accordingly along with the growth of the regulated organs.The specific expression patterns were resulted from the different promoter activity of three GmCYP78 A genes.The soybean plants gained different phenotypes when the three genes were over-expressed,which indicated the differentiation of the three GmCYP78 As after the long-time of selection.3.Natural and artificial selection of the GmCYP78 A subfamily genesAccording to the Ka/Ks ratios of the three GmCYP78 A genes,we knew that all the three genes have evolved under purifying selection(Ka/Ks<1).GmCYP78A70 and GmCYP78A57 partitioned the ancestral gene functions by subfunctionalization.As a new duplicate gene,GmCYP78A72 generally retained most of the functions of its ancestral gene and performed them both in vegetative and reproductive phases.Besides,GmCYP78A72 experienced strong selection,thus retains more functions to deal with the environmental change during the evolution and domestication.So the three GmCYP78 subfamily genes retained via different purifying and artificial selection.