Enzymic properties and capacities of developing tomato (Lycopersicon esculentum L.) fruit plastids

Inhibition of chloroplastic fructose 1,6-bisphosphatase in tomato fruits leads to decreased fruit size, but only small changes in carbohydrate metabolism

“…As expected, the reduction in FBPase activity was greatest in younger fruits. It is known that the cp-FBPase is present in green, but not red, fruits and, therefore, that in older fruits all FBPase activity comes solely from the cy-FBPase (Bu¨ker et al 1998). As it was the cp-FBPase isoform that was being repressed, differences in activity should have been greatest in younger fruits.…”

“…The difference between this study and that of Kossmann et al (1994) is, again, probably because of the difference in how leaves and fruits metabolize sucrose. Tomato fruit chloroplasts contain both an active glucose phosphate and a triose phosphate transporter (Bu¨ker et al 1998) while chloroplasts in leaves are not thought to contain a glucose phosphate transporter as leaves do not appear to accumulate transcript that codes for this transporter (Kammerer et al 1998). Repression of cp-FBPase activity should reduce flux of carbon produced by photosynthesis into starch.…”

“…The cp-FBPase is present in green, but not red fruits, which correlates with a switch from the fruits being photosynthetically active to becoming inactive (Bu¨ker et al 1998). Fruits obtain sugars both directly from photosynthesis, and through import from source leaves via the phloem.…”

“…Fruits obtain sugars both directly from photosynthesis, and through import from source leaves via the phloem. The triose phosphate and glucose phosphate transporters are active in tomato chloroplasts (Bu¨ker et al 1998), indicating that they could in principle both import and export phosphoesters. It is not clear, therefore, what the role of fruit photosynthesis in fruit metabolism is, although it has been estimated to contribute between 10 and 15% of carbon skeletons in green fruits (Tanaka et al 1974).…”

Yield and biosynthesis of nitrogenous compounds in fruits of green bean (Phaseolus vulgaris L cv Strike) in response to increasing N fertilisation

“…In contrast, the enzyme that catalyses glutamate synthesis (NADH-glutamate synthase, GOGAT), although having been detected in fruits, has proved generally less active than GS in the fruits analysed. 12 The few studies on N metabolism in fruits have focused primarily on development and maturity. Here we study the effect of different N doses on the biosynthesis of organic N compounds in fruits and their influence on yield in green bean plants.…”