Antisense Acid Invertase (TIV1) Gene Alters Soluble Sugar Composition and Size in Transgenic Tomato Fruit

Abstract

Invertases (P-fructosidase, EC 3.2.1.26) are a group of related enzymes that hydrolyze Suc to Glc and Fru. Acid invertase has a pH optimum for activity between 3 and 5, whereas neutra1 invertase has a pH optimum of about 7. Acid invertases are divided into vacuolar (or soluble) and extracellular (or insoluble) forms, with acid (Unger et al., 1992) and basic (Laurière et al., 1988) pls, respectively. Neutra1 (or alkaline) invertase is presumed to be localized in the cytosol (Ricardo, 1974). Plant genes for acid invertase have been cloned from tomato (Lycopersicon esculentum Mill.; Klann et al., 1992) and severa1 other plants, a11 sharing homology to the active site of yeast invertase (Unger et al., 1994). In plants acid invertase is thought to be involved primarily in SUC metabolism for energy in growing tissues (ap Rees, 1974), and increasing extracellular invertase activity results in severely stunted growth and inhibition of photosynthesis (von Schaewen et al., 1990).In tomato acid invertase activity is present during fruit development, and hexose sugars stored in the vacuole are

Suppression of the Vacuolar Invertase Gene Prevents Cold-Induced Sweetening in Potato

“…Instead, organic acids and potassium ions rather than sugars are the dominant contributors to the osmotic potential of potato tubers (Bethke et al, 2009). This situation is distinctly different from that in developing tomato fruit, where invertase activity and hexose accumulation function in the hydrolysis of Suc and turgor-driven fruit growth, respectively (Klann et al, 1996). In carrot taproots and in developing muskmelon fruit, vacuolar acid invertase activity is thought to have a similar role in promoting growth by producing hexoses that decrease osmotic potentials and promote water uptake (Tang et al, 1999;Yu et al, 2008).…”

“…In tomato (Solanum lycopersicum), antisense silencing of the acid invertase gene resulted in a 30% reduction in fruit size (Klann et al, 1996). In carrot (Daucus carota) and muskmelon (Cucumis melo), silencing of the acid invertase gene significantly altered plant and root/fruit development (Tang et al, 1999;Yu et al, 2008).…”

Gene and Metabolite Regulatory Network Analysis of Early Developing Fruit Tissues Highlights New Candidate Genes for the Control of Tomato Fruit Composition and Development

“…Reverse genetic approaches have demonstrated that alterations in fruit metabolism/composition may affect fruit development and vice-versa. As an example, increasing fruit Suc content by down-regulating invertase or vacuolar ATPase genes affects fruit growth and fruit size (Klann et al, 1996;Amemiya et al, 2006). Conversely, altering the ethylene-dependent signal transduction networks has a considerable effect on fruit ripening and associated changes, including fruit color, aroma, sugar, and organic acids (Wilkinson et al, 1995;Barry and Giovannoni, 2006;Carrari and Fernie, 2006;Giovannoni, 2007).…”

Sugar Metabolism and Fruit Development in the Tomato

“…There is believed to be a trade-off between fruit sugar content and yield. For example, while the sugar content of tomato fruit increases as a result of the increased ratio of sucrose to hexose through the suppression of vacuolar invertase gene expression, the fruit size decreases (Klann et al, 1996); fruit size and yield generally decrease as fruit sugar content increases in tomato plants grown under salinity stress conditions (Saito et al, 2008;Sarkar et al, 2008). However, fruit size and yield do not appear to decrease in IL8-3 and SIRT-engineered tomato plants, which contain a higher fruit sugar content, as described above; and in other ILs, the fruit yield does not always decrease even if their fruits exhibit high sugar contents (Baxter et al, 2005b).…”