Phylogenetic and Evolutionary Analysis of the Late Embryogenesis Abundant (LEA) Gene Product in Poaceae

The late Embryogenesis Abundant (LEA) protein family obtains a group of stress-induced hyper-hydrophilic proteins that accumulate in response to cellular dehydration. They are generally unstructured polypeptides without a well-defined three-dimensional structure and have been identified in a wide range of organisms from bacteria to higher plants. Herein, we made a phylogenetic and evolutionary analysis for LEA proteins in Poaceae. The full-length LEA protein sequences were acquired by performing the sequence search of sequenced hva1 against Poaceae species in the non-redundant protein database by a BlastX search tool. The sequences were aligned with the Clustal Omega tool. The MEME suite searched for conserved blocks among each LEA protein sequence. Also, the evolutionary relationship among the LEA protein sequences evaluates using the MEGA tool. The results display close sequence similarity not only into the species but also between species. The results demonstrated that LEA proteins cluster into two large subgroups. The overall average evolutionary difference in LEA protein sequence pairs estimated as 0.4022 amino acid substitutions per site from averaging over all sequence pairs. The LEA protein sequences contain a significant percentage of glycine residues but lack cysteine and tryptophan residues. The results indicate the occurrence of homologs in the subgroup before the divergence of the species. However, the expansion of the gene number in the Poaceae was approved by the duplication events in the preexisting genes rather than by the appearance of the altered LEA gene. Our data will provide novel insights for further studies of the Late Embryogenesis Abundant protein family in Poaceae.