TERMINAL FLOWER-1/CENTRORADIALIS inhibits tuberisation via protein interaction with the tuberigen activation complex

Potato tuber formation is a secondary developmental programme by which cells in the subapical stolon region divide and radially expand to further differentiate into starch-accumulating parenchyma. Although some details of the molecular pathway that signals tuberisation are known, important gaps in our knowledge persist. Here, the role of a member of theTERMINAL FLOWER 1/CENTRORADIALISgene family (termedStCEN) in the negative control of tuberisation is demonstrated for what is thought to be the first time. It is shown that reduced expression ofStCENaccelerates tuber formation whereas transgenic lines overexpressing this gene display delayed tuberisation and reduced tuber yield. Protein-protein interaction studies (yeast two-hybrid and bimolecular fluorescence complementation) demonstrate that StCEN binds components of the recently described tuberigen activation complex. Using transient transactivation assays, we show that theStSP6Atuberisation signal is an activation target of the tuberigen activation complex, and that co-expression ofStCENblocks activation of theStSP6Agene by StFD-Like-1. Transcriptomic analysis of transgenic lines misexpressingStCENidentifies early transcriptional events in tuber formation. These results demonstrate that StCEN suppresses tuberisation by directly antagonising the function of StSP6A in stolons, identifyingStCENas a breeding marker to improve tuber initiation and yield through the selection of genotypes with reducedStCENexpression.