Genome-Wide Comparative Analysis of Invertases in the Salicaceae with the Identification of Genes Involved in Catkin Fiber Initiation and Development.

Invertase (INV) irreversibly converts sucrose to glucose and fructose during processes such as differentiation and organ development in plants, especially during the development of trichomes. Systematic identification and analysis of INVs in Salicaceae remain limited. Here, INV genes in Populus deltoides and Salix suchowensis were investigated, and their chromosomal localization, collinearity, gene structures, cis-regulatory elements, and phylogenetic relationships were comprehensively analyzed. Twenty and seventeen INVs were found, respectively, in P. deltoides and S. suchowensis, most of which were derived from a common ancestor and exhibited similar chromosomal distribution and high collinearity. Orthologs between the two species showed conservation of gene structures and promoter regulatory elements. Multi-species phylogenetic analysis identified an evolutionary clade associated with seed fiber development in P. deltoides and S. suchowensis. Further evaluation of INV expression in female catkins at various stages of seed fiber formation verified the predominance of PdeVINV1, PdeVINV2, PdeVINV3, and PdeVINV4 in P. deltoides, as well as SsuVINV1 and SsuVINV2 in S. suchowensis, during critical phases of catkin fiber differentiation. These genes are likely to have significant regulatory roles in the initiation and development of catkin fiber cells. These findings provide a reference for future functional studies of INVs.