Evolutionary transitions in growth habit and flowering time responses to variable environmental signals
have occurred multiple times independently across angiosperms and have major impacts on plant fitness.
Proteins in the SPL family of transcription factors collectively regulate flowering time genes that have
been implicated in interspecific shifts in annuality/perenniality. However, their potential importance in
the evolution of angiosperm growth habit has not been extensively investigated. Here we identify orthologs representative of the major SPL gene clades in annual Arabidopsis thaliana and Mimulus guttatus
IM767, and perennial A. lyrata and M. guttatus PR, and characterize their expression. Spatio-temporal
expression patterns are complex across both diverse tissues of the same taxa and comparable tissues
of different taxa, consistent with genic sub- or neo-functionalization. However, our data are consistent
with a general role for several SPL genes in the promotion of juvenile to adult phase change and/or flowering time in Mimulus and Arabidopsis. Furthermore, several candidate genes were identified for future
study whose differential expression correlates with growth habit and architectural variation in annual
versus perennial taxa.