The Origin And Evolution Of DELLA Gene Family In Angiosperm

The DELLA gene family is an important member of the GRAS transcription factor superfamily,which is a major regulator of gibberellin signal in plants.The structure,cloning and functional expression of DELLA-encoded genes,the molecular mechanism of the interaction between GA and other plant hormones,and the molecular mechanism of interaction with other plant hormones have been well studied.But little is known about the origin and evolution of the entire DELLA gene family in plants.In this study,we investigate the evolutionary relationshipswithin angiosperms based on the amino acid sequences of the DELLA gene in the major branch groups of plants.Our research will shed light on the further understanding oftheevolution of the DELLA family in plants.Firstly,the phylogenetic framework of the DELLA gene family in the angiosperms wasreconstructed based on sequences from model plants.DELLA gene sequences were collected froma total of 11 model angiosperms species from 11 families.Phylogenetic analysis suggested thatall angiosperms DELLA sequences form a well-supported group with bootstrap of 100%,except for two sequences from Rosaceae.Gene replication is found in dicotyledon,resulted in two large branches and each containing two major groups of rosids and asterids.But the copy number of the gene contained in the different species is not consistent.There is probably a relict lineage in angiosperms.Secondly,on the basis of the previous phylogenetic framework,we explore the relationship between the copy number and evolutionary relationship of DELLA gene family in Vitaceae using tanscriptome data.The relationship between the genetic distance and the conserved domains were also discussed.Our results suggested that the DELLA gene family was divided into three branches,two of whichare close to each other and the third is confirmed to be one of the relict lineage in the angiosperm.The domain search was performed usisng the Pfam database and the domain was annotated using the MEME software.There was a significant difference in the N-terminal domain in the grape family.The conserved motifs of GROUP1 lacked the conserved loci of motif 4,11,15,17,18,22,when compared with GROUP2 and GROUP3,which may be due to the conserved statusof motifs in GROUP1 and more amino acidsmutation anddifferentiationin the later two groups.Finally,the genome database of all plants was serarched to obtain the sequences of all DELLA genes,and the comprehensive phylogenetic relationship of DELLA gene family in plants was reconstructed.The relationships between gene motif and conserved domain mutation and phylogenetic evolution was also examined.The phylogenetic relationship of the DELLA gene family in angiosperms indicated that the DELLA gene family has begun to differentiate before the origin of the angiosperms.At least from the seed plants,an early gene replication event occurs,leading into two branches.One is the main lineage of Angiosperm clade I,which includes all groups of angiosperms.Two copies are found in the dicotyledonous plants in this clade.The second clade is relict in angiosperms with sequences from only some partial taxa.The C-terminal GRAS domain of the DELLA gene is highly conserved,and the N-terminal domain is variable in different groups.