Genetic basis of the link between senescence regulation and flowering time control

In annual plants leaf senescence is often linked to reproduction. However, no effect of sterility on senescence was found using mutants of Arabidopsis, suggesting that senescence in Arabidopsis is not regulated by the successful formation of fruits and seeds. Nevertheless, flowering time and senescence are correlated among different accessions of Arabidopsis, indicating that floral initiation and senescence are linked, although the causal relationship remained unresolved. Analysing the effect of sugar supply on senescence in recombinant-inbred lines (RILs) we found that while sugar treatment induced senescence in early-flowering lines, the effect was less pronounced in late-flowering lines. Microarray analysis revealed differences in the expression of flowering genes, such as FLC and SOC1, in the RILs. Quantitative trait locus (QTL) analysis was conducted to determine the genetic basis of this regulation. A major QTL mapped to the top of chromosome IV where FRI, an activator of the floral repressor FLC, is localised. Since interaction of functional FRI and FLC alleles results in vernalisation dependence of flowering, the effect of vernalisation on senescence was determined in early- and late late-flowering lines. Whereas a clear correlation between flowering and senescence was found without vernalisation, vernalisation abolished differences between the lines, thus supporting the genetic link between the vernalisation-dependent pathway of flowering and senescence regulation revealed by the QTL analysis.