Leaf-specific antisense inhibition of starch biosynthesis in transgenic potato [Solanum tuberosum] plants leads to an increase in photoassimilate export from source leaves during the light period

• Published in: Plant and cell physiology Vol. 36; no. 4; pp. 615 - 624
• Main Authors: Leidreiter, K. (Universitaet Goettingen (Germany)), Heineke, D, Heldt, H.W, Mueller-Roeber, B, Sonnewald, U, Willmitzer, L
• Format: Journal Article
• Language: English
• Published: 01.06.1995
• Subjects: adenosine diphosphate; ALMIDON; AMIDON; ANTIMETABOLITE; ANTIMETABOLITES; ANTIMETABOLITOS; antisense DNA; BIOCHEMICAL REACTIONS; BIOSINTESIS; BIOSYNTHESE; BIOSYNTHESIS; diurnal variation; ECLAIRAGE; enzyme activity; enzyme inhibitors; FEUILLE; FOTOSINTESIS; genetic regulation; glucose; growth; HOJAS; ILUMINACION; inhibition; LEAVES; light; LIGHTING; malic acid; metabolites; NUTRIENT TRANSPORT; phosphorylase; photosynthates; PHOTOSYNTHESE; PHOTOSYNTHESIS; plant development; PLANTAS TRANSGENICAS; PLANTE TRANSGENIQUE; quantitative analysis; REACCIONES BIOQUIMICAS; REACTION BIOCHIMIQUE; SOLANUM TUBEROSUM; source-sink relationships; STARCH; sugars; TRANSGENIC PLANTS; TRANSPORT DES SUBSTANCES NUTRITIVES; TRANSPORTE DE NUTRIENTES; tubers
• ISSN: 0032-0781; 1471-9053
• DOI: 10.1093/oxfordjournals.pcp.a078801

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 rhythms of carbon export from leaves and utilization by the major storage sinks, i.e. developing tubers.