LAUSR

Abstract MADS box transcription factors encoded by APETALA1/FRUITFUL (AP1/FUL-like) genes are key regulators of flowering in angiosperms. Here, two such genes were isolated from the ornamental species Chrysanthemum morifolium cultivar ‘Jinba’. One of the genes (CmAP1L1) was shown to belong to the AP1 clade, and the other (CmFL2) to the FUL clade. Despite their phylogenetic difference, their transcriptional behavior was similar: in plants prior to flowering, both genes were strongly transcribed in the leaves, while in plants which had reached the reproductive stage, their transcription was most abundant in young buds (2–4 mm in diameter) and was at only a low level in the mature inflorescence. Both proteins were localized in the nucleus as well as in the cell membrane. Their over-expression in both cases accelerated flowering, which was also the case when they were constitutively expressed in Arabidopsis thaliana. While the transcription of CmAP1L1 followed an atypical circadian rhythm, that of CmFL2 was arrhythmic. This work suggested that the AP1/FUL-like genes might play a conserved function in promoting flowering in different species.