The transcriptional changes underlying the flowering phenology shift in response to climate warming

Climate warming is causing shifts in key life-history events, such as flowering time. To assess the impacts of climate warming on flowering phenology, it is crucial to understand the transcriptional changes of genes underlying the phenological shifts. Here, we comprehensively explore genes that contribute to the flowering phenology shifts under climate warming by monitoring the latitudinal gradient of seasonal expression dynamics of 293 flowering-time genes in a perennial herb, Arabidopsis halleri. Through transplant experiments conducted at northern, southern, and subtropical study sites in Japan, we have demonstrated that the flowering period was shortened with decreasing latitude and ultimately, the plants lost the opportunity to flower in subtropical climates. The key transcriptional changes underlying the shift in flowering phenology and the loss of flowering opportunity were the diminished expression of floral pathway integrator genes and genes in the gibberellin synthesis and aging pathways, all of which are suppressed by increased expression of FLOWERING LOCUS C, a central repressor of flowering. These results suggest that the upper-temperature threshold beyond which plants cannot reproduce in response to warming is governed by a relatively small number of genes that suppress reproduction in the absence of winter cold.