Roles of gibberellins in increasing sink demand in Japanese pear fruit during rapid fruit growth |
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Authors: | Caixi Zhang Kenji Tanabe Fumio Tamura Akihiro Itai Masashi Yoshida |
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Institution: | (1) Department of Plant Science, College of Agriculture and Biology, Shanghai Jiaotong University, Shanghai, 201101, China;(2) Laboratory of Horticultural Science, Faculty of Agriculture, Tottori University, Tottori 680-8553, Japan |
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Abstract: | Our previous work demonstrated that exogenous gibberellins (GAs) applications during rapid fruit growth significantly increases
sink demand and results in a larger fruit in Japanese pear. In an attempt to unravel the mechanism of increased sink demand
by applied GAs, the histology, cell wall components of the flesh, and carbon accumulation in the fruit were assessed for Japanese
pear (Pyrus pyrifolia, cultivar ‘Kousui’), as were the activities of sucrose- and sorbitol-cleaving enzymes. Our results show that most vascular
tissues occurred in core tissue with very little vascular tissue in the flesh. Application of a mixture of GA3 + GA4 in lanolin paste significantly increased the amount of ethanol-insoluble solids, e.g., total pectins, hemicellulose, and
cellulose in the cell walls. There was a significantly increased sink demand (assessed by 13C accumulation in the fruit) by the applied GAs, and this increased sink strength was closely related to increased activities
of cell wall-bound invertase in the core, neutral invertase and NAD-dependent sorbitol dehydrogenase in the flesh during rapid
fruit growth. As well, concentrations of sorbitol and sucrose in the flesh were decreased by GA application, while glucose
concentration increased. Most importantly, the fact that sink activity can be increased by GA application implies that endogenous
GAs are likely to be important modulators for sugar metabolism. Hence, selecting for genotypes with elevated GA production
in the growing fruit and increased activities of key enzymes for sugar metabolism could result in increased fruit size. |
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Keywords: | Pyrus pyrifolia Nakai Japanese pear Sink demand Sorbitol and sucrose catabolism Gibberellins |
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