Regulatory mechanism of GA on tuber growth by DELLA-dependent pathway in yam (Dioscorea opposita).

Endogenous and exogenous GA responses to DoEXP and DoXTH depend on the DoGA20ox1, DoGA3ox1, DoGA2ox3, DoGA2ox4, DoGID1a, and DoDELLA1 to regulate yam tuber growth. Yam tuber undergoes significant alteration in morphogenesis and functions during growth, and gibberellins (GA) are considered potentially important regulators of tuber growth. However, it is little known about the regulation of GA metabolism and GA signaling components genes in tuber growth of yam. In this study, the cloning and expressions of GA level, GA metabolism and signaling genes, and cell wall genes in tuber growth in response to GA and GA biosynthesis inhibitor paclobutrazol (PP) treatments were studied. The contents of GA accumulated at the tuber growth, with the highest levels in the early expansion stage. DoGA20ox1, DoGA3ox1, and four DoGA2ox genes were significantly abundant in the early expansion stage of tuber and gradually declined along with tuber growth. Three DoGID1 and three DoDELLA genes were showed different expression patterns in the early expansion stage of tuber and gradually declined along with tuber growth. Five DoEXP and three DoXTH genes expression levels were higher in the early expansion stage than in other stages. Exogenous GA increased endogenous GA levels, whereas the expression levels of DoGA20ox1, DoGA3ox1, DoGID1a, and DoDELLA1 were down-regulated in the early expansion stage of tuber by GA treatment, DoGA2ox3 and DoGA2ox4 were up-regulated. PP application exhibited opposite consequences. Thus, a mechanism of GA regulating yam tuber growth by DELLA-dependent pathway is established.