Phytochrome interacting factors (PIFs) in Solanum lycopersicum: diversity, evolutionary history and expression profiling during different developmental processes

Although the importance of light for tomato plant yield and edible fruit quality is well known, the PHYTOCHROME INTERACTING FACTORS (PIFs), main components of phyto-chrome-mediated light signal transduction, have been studied almost exclusively in Arabi-dopsis thaliana. Here, the diversity, evolution and expression profile of PIFgene subfamily in Solanum lycopersicum was characterized. Eight tomato PIF loci were identified, named SlPIF1a, SlPIF1b, SlPIF3, SlPIF4, SlPIF7a, SlPIF7b, SlPIF8a and SlPIF8b. The duplication of SlPIF1, SlPIF7 and SlPIF8 genes were dated and temporally coincided with the whole-genome triplication event that preceded tomato and potato divergence. Different patterns of mRNA accumulation in response to light treatments were observed during seedling dee-tiolation, dark-induced senescence, diel cycle and fruit ripening. SlPIF4 showed similar expression profile as that reported for A. thaliana homologs, indicating an evolutionary conserved function of PIF4 clade. A comprehensive analysis of the evolutionary and transcriptional data allowed proposing that duplicated SlPIFs have undergone sub- and neo-functionalization at mRNA level, pinpointing the importance of transcriptional regulation for the maintenance of duplicated genes. Altogether, the results indicate that genome polyploi-dization and functional divergence have played a major role in diversification of the Solanum PIF gene subfamily.