In a PNAS article entitled, “Conserved genetic determinant of motor organ identity in Medicago truncatula and related legume,’ published online on the 16th July, Jianghua and six of his associates affiliated to 4 different institutes have suggested that by swelling and shrinking, the cells at opposite sides of the pulvinus are involved in directing leaf or leaflet movements. From M. truncatula these workers isolated a mutant called elongated petiolule1 (elp1). This mutant fails to fold its leaflets in the dark due to loss of motor organs. Their findings on map-based cloning indicated that ELP1 encodes a putative plant-specific LOB (Lateral Organ Boundaries) Domain transcription factor and that ELP1 is expressed in primordial cells that develop into the motor organ. Furthermore, the epidermal cells showed characteristics of motor organ. Ectopic expression of ELP1 resulted in dwarf plants with petioles and rachises reduced in length. It was further shown that the motor organ is regulated by a conserved molecular mechanism.