Abstract:In order to improve water stress tolerance of tomato (Solanum lycopersicum) plants, an expression vector containing an arabidopsis 14-3-3 protein, Arabidopsis General Regulatory Factor 9 (AtGRF9) cDNA driven by a cauliflower mosaic virus 35S promoter was transferred into tomato plants. Tomato wild-type (WT), two lines of GRF9-overexpressing tomato plants (E2, E7) were treated with 20% polyethylene glycol (PEG6000) to induce water stress under hydroponic culture conditions. Results showed: 1) The degree of water stress tolerance of transgenic tomato plants was found to be significantly greater than that of wild-type tomato plants as measured by root architecture development. The relative inhibition ratio of total root length of three lines tomato plants (WT, E2, E7) was 43%, 28% and 30%, respectively; the relative inhibition ratio of root surface area of three lines tomato plants (WT, E2, E7) was 46%, 33% and 35%, respectively; the relative inhibition ratio of root volume of three lines tomato plants (WT, E2, E7) was 47%, 32% and 29%, respectively; the relative inhibition ratio of root diameter of three lines tomato plants (WT, E2, E7) was 29%, 21% and 22%, respectively. 2) GRF9 favored the accumulation of sucrose in transgenic tomato (E2, E7) roots, and the root dry weight was 23% higher than that of WT. 3) In addition, GRF9 enhanced the activity of plasma membrane H+-ATPase in transgenic tomato (E2,E7) roots, and the root proton secretion was 35% higher than that of WT. Taken together, all the results indicated that under PEG-induced water stress, GRF9 is involved in enhancing proton secretion and accumulating more sucrose in the root to guarantee greater root architecture development on total root length, root surfaces area, root volume and root diameter. Therefore, Arabidopsis GRF9 plays an important role for tomato plants response to water stress.