Leaf-Specific Antisense Inhibition of Starch Biosynthesis in Transgenic Potato Plants Leads to an Increase in Photoassimilate Export from Source Leaves during the Light Period : GENE STRUCTURE AND EXPRESSION : PROTEINS, ENZYMES AND METABOLISM

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In an attempt to study the importance of starch synthesis in leaves with respect to sink-source interactions, we investigated daily turnover of carbohydrates in leaves of transgenic potato plants inhibited for ADP-glucose pyrophosphorylase (AGPase). Down-regulation of AGPase has been performed using two different promoters: the near-constitutive CaMV 35S promoter, and the ST-LS1 promoter which is active in photosynthetic cells only. Residual AGPase activity in leaves was between 6 and 30% in individual transformants as compared to wild-type potato plants. We found that: (i) photosynthesis is not significantly altered relative to wild-type plants; (ii) levels of starch are markedly reduced in leaves of transgenic plants; (iii) levels of soluble sugars and malate are largely unaffected by the inhibition of AGPase; (iv) the reduction of starch synthesis leads to a higher portion of assimilated carbon being transported from leaves to sink tissues during the light period; (v) altered leaf export characteristics do not change tuber yield under greenhouse conditions. Collectively, these data demonstrate a striking flexibility of the potato plant with respect to day/night rhyihms of carbon export from leaves and utilization by the major storage sinks, i.e. developing tubers.
日本植物生理学会の論文