Sucrose function on the bulbil formation of Lilium lancifolium

Lilium lancifolium is an important ornamental, edible and medicinal plant in China.Bulbil is the main propagation organ of L.lancifolium. Studies have shown that high concentration of sucrose can significantly promote the formation of bulbil in vitro, but the detail function mechanism of sucrose on the process of bulbil formation in lily has not been reported. In this study, we investigated the osmotic regulation, carbon source and signal molecular functions of sucrose during bulbil formation using L.lancifolium as material. Results indicated that the optimal concentration of sucrose inducing bulbil formatin was 262.93 mM. The results of osmotic potential and soluble sugars experiments indicated that the effect of sucrose on bulbil formation of L.lancifolium was not connected to its osmotic potential, nor entirely explained by it's function as carbon source and energy. We used non-metabolic sugar analogues to study the effect of sucrose specific signaling on bulbil formation. Results indicated that exogenous 3-OMG could not induce bulbil formation. Whereas palatinose could induce bulbil formation, although the induction time was delayed compared with control, further indicating the specific signalling of sucrose. The results of sugar absorption inhibitor experiments showed that sucrose induced the bulbil formation by itself and by its decomposed hexose. In addition, gene expression analysis was performed in leaf axils. The results showed that high sucrose concentration may promote the formation of bulbil by inducing the expression of SUS2, SUT2 and WOX11 genes. Overall, the effect of sucrose on inducing bulbil formation could be explained by it's function of carbon source and signaling molecule.