JOINTLESS is a MADS-box gene controlling tomato flower abscissionzone development

Abscission is a universal and dynamic process in plants whereby organssuch as leaves, flowers and fruit are shed, both during normal development,and in response to tissue damage and stress1. Shedding occursby separation of cells in anatomically distinct regions of the plant, calledabscission zones (AZs). During abscission, the plant hormone ethylene stimulatescells to produce enzymes that degrade the middle lamella between cells inthe AZ. The physiology and regulation of abscission at fully developed AZsis well known2,3, but the molecular biology underlying theirdevelopment is not. Here we report the first isolation of a gene directlyinvolved in the development of a functional plant AZ. Tomato plants with the jointless mutation4 fail to develop AZs on their pedicelsand so abscission of flowers or fruit does not occur normally. We identify JOINTLESS as a new MADS-box gene in a distinct phylogenetic clade separatefrom those functioning in floral organs. We propose that a deletion in JOINTLESS accounts for the failure of activation of pedicel AZ developmentin jointless tomato plants.