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Kyle M. VandenLangenberg, Paul C. Bethke and James Nienhuis

associated with organic acids, bitterness is often the result of phenolic compounds, saltiness is attributable to sodium or potassium, and sweetness is the result of sugars, including fructose, glucose, and sucrose ( Sims and Golaszewski, 2003 ). Sugars not

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Riccardo Lo Bianco and Mark Rieger

The peach [Prunus persica (L.) Batsch (Peach Group)] fruit is a sink organ comprised of different types of tissue, which undergoes three distinct developmental stages during the growth season. The objective of this study was to characterize the activity and partitioning of sorbitol and sucrose catabolism within `Encore' peach fruit to determine whether the two forms of translocated carbon play different roles in the various fruit tissues and/or stages of development. Sorbitol catabolic activity was defined as the sum of NAD-dependent sorbitol dehydrogenase (SDH) and sorbitol oxidase (SOX) activities, whereas sucrose catabolic activity was defined as the sum of sucrose synthase (SS), soluble acid invertase (AI), and neutral invertase (NI) activities. Partitioning of sorbitol and sucrose catabolism in each tissue was calculated as percentage of total sorbitol or sucrose catabolic activity in the entire fruit. At cell division, sorbitol catabolic activity was similar in the endocarp and mesocarp, but lower in the seed. However, sorbitol catabolism was mostly partitioned into the mesocarp, due to its large size compared to that of other tissues. SDH was more active in the mesocarp, while SOX was more active in the endocarp. Sucrose catabolism was most active and partitioned mainly into the endocarp. At endocarp hardening, both sorbitol and sucrose catabolic activities were highest in the seed, but despite this, sucrose catabolism was partitioned mostly in the mesocarp. At cell expansion, sorbitol and sucrose catabolic activities were still higher in the seed only when expressed on a weight basis and similar in mesocarp and seed when expressed on a protein basis. Both sorbitol and sucrose catabolism were partitioned mostly into the mesocarp. Sorbitol and sucrose contents were generally higher in the tissues that exhibited lower catabolic activities. All carbohydrates were always partitioned mostly into the mesocarp. Our results show that, at the cell division and endocarp hardening stages, sorbitol and sucrose catabolism are partitioned differently in the fruit and that SDH activity may play an important role in mesocarp cell division and final fruit size determination.

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Takaya Moriguchi, Kazuyuki Abe, Tetsuro Sanada and Shohei Yamaki

Abbreviations: DTT, dithiothreitol; NAD+-SDH, NAD+-dependent sorbitol dehydrogenase; SPS, sucrose-phosphate synthase; SS, sucrose synthase. 1 Present address: Laboratory of Horticulture, School of Agriculture, Nagoya Univ., Chikusa, Nagoya, 464

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Silver Tumwegamire, Regina Kapinga, Patrick R. Rubaihayo, Don R. LaBonte, Wolfgang J. Grüneberg, Gabriela Burgos, Thomas zum Felde, Rosemary Carpio, Elke Pawelzik and Robert O.M. Mwanga

and Mozambique ( Mwanga et al., 2009 ). The present study evaluated selected East African sweetpotato accessions for storage root quality (DM, protein, starch, sucrose, β-carotene, Fe, Zn, calcium, and magnesium) and obtained information on the

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Yosef Burger and Arthur A. Schaffer

Fruit quality of melon is determined primarily by its sugar content ( Yamaguchi et al., 1977 ). The mature fruit sugar content in sweet melons is comprised of the disaccharide sucrose and its two hydrolysis products, the hexoses glucose and

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Takaya Moriguchi, Tetsuro Sanada and Shohei Yamaki

Sugar levels and composition were determined in developing `Hakuto' peach (Prunus persica Batsch var. vulgaris Maxim.) fruit. Glucose and fructose in nearly equal amounts were the predominant sugars detected during the early stage of development. Sucrose subsequently began to accumulate and was the predominant sugar in mature fruit. Sorbitol remained at a low level throughout development. The large increase in the amount of sucrose was accompanied by a rapid increase in sucrose synthase (EC 2.4.1.13) activity. Sucrose phosphate synthase (EC 2.4.1.14) was also detected in flesh extracts, but the activities were low throughout development. Acid invertase (EC 3.2.1.26) activity was highest in young fruit and declined with development. Activity, however, increased again at a later stage of development. Peach fruit contained appreciable sorbitol oxidase activity, while other sorbitol-related enzymes were barely detectable, suggesting that transported sorbitol was predominantly converted to glucose. These results suggest that the supply of glucose and fructose depends on acid invertase and sorbitol oxidase, and that accumulation of sucrose depends on-sucrose synthase.

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Jinmin Fu, Bingru Huang and Jack Fry

carbohydrates provide energy and solutes for osmotic adjustment. Sucrose, an important component of TNC, is the dominant form of carbohydrate transported to developing plant organs and is one of the sugars stored in higher plants ( Khayat and Zieslin, 1987

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Fang Yu, Zhiming Ni, Xingfeng Shao, Lina Yu, Hongxing Liu, Feng Xu and Hongfei Wang

Peaches [ Prunus persica (L.) Batsch] are one of the most important fruit crops in the world and are priced because of their rich flavor and nutritional value. Sucrose is the major sugar present, contributing around 75% of total sugar in the fruit

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Xiyan Yu, Xiufeng Wang, Jide Fan, Hongmei Tian and Chengchao Zheng

, and the onset of sucrose accumulation ( Lester and Dunlap, 1985 ). Attempts to elucidate the changes in metabolism that lead to accumulation of sucrose have focused on sucrose-metabolizing enzymes during fruit growth and development ( Geromel et al

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Natalie L. Hubbard, D. Mason Pharr and Steven C. Huber

Abbreviations: CER, net carbon exchange rate; DAA, days after an thesis; SPS, sucrose phosphate synthase. Cooperative investigation of the North Carolina Agricultural Research Service, U.S. Dept. of Agriculture, and Agricultural Research Service