Interactions between flowering and senescence regulation and the influence of low temperature in Arabidopsis and crop plants

Growth temperature affects flowering and senescence in plants. For example, prolonged exposure to cold temperature, that is vernalisation, is required to induce flowering in winter crops and winter-annual Arabidopsis lines. In winter-annual Arabidopsis plants, vernalisation can also accelerate leaf senescence. Cold acclimation, in contrast, delays flowering and senescence, probably by activating the expression of the floral repressor FLOWERING LOCUS C (FLC). In addition, it has been shown for Arabidopsis and wheat that a feedback mechanism inhibits cold acclimation once flowering has been initiated. In this review, the interactions between flowering and senescence regulation are analysed based on findings for mutants and transgenic Arabidopsis plants. Both independent and common pathways regulating these two life-history traits are described. Using transcription factors that are involved in flowering and senescence regulation as baits, a transcriptional network was constructed based on correlation of gene expression. Opposite effects of senescence-promoting transcription factors on gene expression indicate the existence of feedback loops. Genes identified in the network include, for example, genes for leucine-rich repeat transmembrane protein kinases, which have recently been implicated in senescence regulation in barley. Promoter motif analysis suggests that flowering and senescence regulation are closely associated with light and stress signalling. The role of temperature was explored by constructing a transcriptional network for cold-responsive genes that were shown to be induced in plants with delayed senescence. This network highlights the importance of circadian regulation. The implications of these regulatory interactions for crop production are discussed.