FLOWERING LOCUS Cdrives delayed flowering inArabidopsisgrown and selected at elevated CO2

Abstract

SummaryAltered flowering time at elevated [CO2] is well documented, although mechanisms are not well understood. AnArabidopsisgenotype previously selected for high fitness at elevated [CO2] (SG) showed delayed flowering and larger size at flowering when grown at elevated (700 ppm) versus current (380 ppm) [CO2]. This response was correlated with prolonged expression ofFLOWERING LOCUS C(FLC), a vernalization-responsive floral repressor gene.To determine ifFLCdirectly delays flowering at elevated [CO2] in SG, we used vernalization (extended cold) to downregulateFLCexpression. We hypothesized that vernalization would eliminate delayed flowering at elevated [CO2] through the direct reduction ofFLCexpression, eliminating differences in flowering time between current and elevated [CO2].We found that with downregulation ofFLCexpression via vernalization, SG plants grown at elevated [CO2] no longer delayed flowering compared to current [CO2]. Thus, vernalization returned the earlier flowering phenotype, counteracting effects of elevated [CO2] on flowering.This study indicates that elevated [CO2] can delay flowering directly throughFLC, and downregulation ofFLCunder elevated [CO2] reverses this effect. Moreover, this study demonstrates that increasing [CO2] may potentially drive major changes in development throughFLC.