Genome-wide identification of expansin genes in Brachypodium distachyon and functional characterization of BdEXPA27

Plant expansin belongs to a group of cell wall proteins and functions in plant growth and development. However, limited data are available on the contributions of expansins in Brachypodium distachyon. In the present study, a total of 38 expansins were identified in B. distachyon genome. Phylogenetic analysis divided the expansins into four groups, namely EXPA, EXPB, EXLA, and EXLB. Chromosomal distribution showed that they were unevenly distributed on 4 chromosomes. A total of six tandem duplication pairs and four segmental duplication pairs were detected, which contributed to the expansion of the B. distachyon expansin gene family. Expansins in the same group shared similar gene structure and motif composition. Three types of cis-elements, development-related, hormone-related, and abiotic stresses-related elements were found in the B. distachyon expansin gene promoters. Expression profiles indicated that most of B. distachyon expansin genes participate in plant development and abiotic stress responses. Overexpression of BdEXPA27 increased seed width and length, root length, root hair number and length in Arabidopsis and showed higher germination rate in transgenic lines. This study establishes a foundation for further investigation of B. distachyon expansin genes and provides novel insights into their biological functions.