Roles played by invertase and gene expression in the development of the horn-shaped gall on leaves of Rhus chinensis

The present study deals with the growth and development of the horn-shaped gall, which is induced by Schlechtendalia chinensis Bell. on leaves of Rhus chinensis Mill. The relationship between gall formers and their host plants was investigated by means of the activities of various invertases, the expressions of the cell wall invertase gene (INV2), and vacuolar invertase gene (INV3) during gall development. Our results show that the increase in the sink strength of the galls required cell wall invertase and vacuolar invertase, and that vacuolar invertase had a particular impact during the early development. In addition, vacuolar invertase activity was always significantly higher in galls than in leaves. However, ionically bound cell wall invertase showed a slightly significant increased activity level when compared with the leaves after galls had entered the fast growing period. This result indicates that vacuolar invertase is related to the rapid expansion of the galls, but ionically bound cell wall invertase is involved in the rapid growth of tissues. The enhanced activity of cell wall invertase and the expression of INV2 may be a plant response to a gall-induced stress. Cytoplasmic invertase that acts as a maintenance enzyme, or takes part in the production of secondary metabolites, was elevated when intracellular acid invertase activity decreased.