Synopsis of the Plant-Specific Gene Family.

was previously identified as a suppressor of the long-hypocotyl phenotype in Overexpression of conferred dwarf phenotypes similar to those observed in plants containing elevated levels of cytokinin (CK) nucleotides and nucleosides. Two B-IVE- IKE (SOFL) proteins, AtSOFL1 and AtSOFL2, which are more similar at the protein level to each other than they are to SOB5, conferred similar phenotypes to the mutant when overexpressed. We used protein sequences of founding gene family members to perform database searches and identified a total of 289 homologs in genomes of 89 angiosperm species. Phylogenetic analysis results implied that the gene family emerged during the expansion of angiosperms and later evolved into four distinct clades. Among the newly identified gene family members are four previously unreported Multiple sequence alignment of the 289 SOFL protein sequences revealed two highly conserved domains; SOFL-A and SOFL-B. We used overexpression and site-directed mutagenesis studies to demonstrate that SOFL domains are necessary for and overexpression phenotypes. Examination of the subcellular localization patterns of founding SOFLs suggested they may be localized in the cytoplasm and/or the nucleus. Overall, we report that are a plant-specific gene family characterized by two conserved domains that are important for function.