Invertase Activity and Related Genes Expression Analysis in Parthenocarpic and Non-parthenocarpic Cherry Tomato (Solanum lycopersicum var. cerasiforme) Inbred Lines
Abstract：Sucrose metabolism plays important roles in the development of plant sink organs, particularly in the process of fruit-setting and fruit development. Invertase (INV; EC 3.2.1.26) hydrolyzing sucrose into glucose and fructose is a key player in sucrose metabolism. Through exploring the correlation between INV enzyme activity, related genes expression characteristics and parthenocarpy, this study was to provide candidate genes and a theoretical basis for understanding the molecular mechanism of sucrose metabolism regulating plant fruit-setting. A parthenocarpic (CP28) and a non-parthenocarpic (CL26) cherry tomato (Solanum lycopersicum var. cerasiforme) inbred line were taken as materials to investigate the INV activities, sugar contents and INV genes expression patterns in buds, flowers and fruits under different developmental stages. The results indicated that cell wall invertase (CWIN) activities of buds and flowers were higher than those of fruits in both CP28 and CL26 lines, and moreover, the CWIN activity of CP28 was significantly higher than that of CL26 in middle bud stage (P＜0.05). The expression patterns of genes encoding tomato CWIN (Lin5, Lin6 and Lin7) and CWIN inhibitor (SlINVINH1) in buds and flowers of both CP28 and CL26 lines were analyzed by qRT-PCR. The results showed that the relative expression levels of Lin6 in buds and flowers of CP28 line were about 93~ 205 times of those of CL26 line, i.e. significantly higher than those of CL26 line (P＜0.01). Meanwhile, the expression patterns of Lin5, Lin7 and SlINVINH1 showed no significant difference between the 2 lines. Taken together, these results indicated that Lin6 was likely the key tomato CWIN gene taking part in the regulation of tomato fruit parthenocarpy through sucrose metabolism. This finding provides helpful information for further understanding the molecular mechanism of CWIN participating in the regulation of parthenocarpy in tomato fruit.
