A MADS domain gene involved in the transition to flowering in Arabidopsis

Flowering time in many plants is triggered by environmental factors that le ad to uniform flowering in plant populations, ensuring higher reproductive success. So far, several genes have been identified that are involved in fl owering time control. AGL20 (AGAMOUS LIKE 20) is a MADS domain gene from Ar abidopsis that is activated in shoot apical meristems during the transition to flowering. By transposon tagging we have identified late flowering agl2 0 mutants, showing that AGL20 is involved in flowering time control. In pre viously described late flowering mutants of the long-day and constitutive p athways of floral induction the expression of AGL20 is down-regulated, demo nstrating that AGL20 acts downstream to the mutated genes. Moreover, we can show that AGL20 is also regulated by the gibberellin (GA) pathway, indicat ing that AGL20 integrates signals of different pathways of floral induction and might be a central component for the induction of flowering. In additi on, the constitutive expression of AGL20 in Arabidopsis is sufficient for p hotoperiod independent flowering and the overexpression of the orthologous gene from mustard, MADSA, in the classical short-day tobacco Maryland Mammo th bypasses the strict photoperiodic control of flowering.