Yoshinori Kanayama

Two divergent genes encoding fructokinase, Frk1 and Frk2, have been previously shown to be expressed in tomato (Lycopersicon esculentum L.) and have now been further characterized with regard to their spatial expression and the enzymic properties of the encoded proteins. Frk1 and Frk2 mRNA levels were coordinately induced by exogenous sugar, indicating that both belong to the growing class of sugar-regulated genes. However, in situ hybridization indicated that Frk1 and Frk2 were expressed in a s

The accumulation of nitrite in nodules was investigated to elucidate the mechanism of inhibition of nitrogen fixation in nodules of soybean (Glycine max. [L.] Merr.) plants supplied with nitrate. Acetylene-reducing activity (ARA) in nodules fell within 24 h as a result of the supply of exogenous nitrate, accompanied by an increase in the accumulation of nitrite in the cytosol but not in the bacteroids of nodules. Nitrate reductase (NR) activity in the nodule cytosol remained high, irrespective o

Sugars are strongly related to fruit yield and quality, playing a critical role in fruit set, growth, ripening, and composition. The tomato (Solanum lycopersicum) is not only an important horticultural crop, but also a useful experimental model plant that can be used to further our understanding of fruit physiology. Therefore, in this review, we consider sugar metabolism and fruit development in the tomato. We begin by discussing how the sugar content of tomato fruit has been successfully increa

Sucrose is generally considered the primary photosynthate in plants; however, many horticultural crops, including rosaceous fruit trees, synthesize and use polyols (sugar alcohols). This review describes recent progress in physiological research on the metabolism and transport of sorbitol in rosaceous fruit trees, and of mannitol, another common polyol, in horticultural crops. Studies on various polyols other than sorbitol (in rosaceous fruit trees) and mannitol are then described. Polyols play

Sorbitol-6-phosphate dehydrogenase (S6PDH) is known to be a key enzyme in the biosynthesis of sorbitol, an early product of photosynthesis, common to fruit trees of the Rosaceae family. Effects of low temperature and abscisic acid (ABA) on the expression of the S6PDH gene were investigated in apple leaves. In leaf-disc experiments, the expression of S6PDH was enhanced by an ABA treatment, as well as by low temperature and high-salinity stresses. The level of S6PDH mRNA increased 8 h after the ad

NADP-dependent sorbitol-6-phosphate dehydrogenase (S6PDH) was purified from apple (Malus domestica) seedlings by a purification procedure that included two fractionations by affinity chromatography. The purified enzyme was a homogeneous protein that migrated as a single polypeptide chain with an apparent relative mass of 36,000 during SDS-polyacrylamide gel electrophoresis and the native enzyme was a homodimer of the polypeptide. The maximum velocity of the reduction of glucose-6-phosphate (G6P)