Increases of 3‐phosphoglyceric acid in potato plants through antisense reduction of cytoplasmic phosphoglycerate mutase impairs photosynthesis and growth, but does not increase starch contents

Abstract

AbstractA full‐length cDNA encoding cytosolic phosphoglycerate mutase (PGAM; E.C. 5.4.2.1) from potato (Solanum tuberosum L.) was isolated. RNA blots indicated that the accumulation of PGAM transcript was similar in all organs studied. Transgenic potato plants with either constitutive, or tuber‐specific, decreases in PGAM expression were created. Constitutive reduction of enzyme activity of down to 25% of the control resulted in increased 3‐PGA contents of up to 30% in leaves, but also led to reduced growth rates, probably due to a reduction of photosynthetic activity. Soluble carbohydrates and starch in leaves were reduced, and the tuber yield of the plants was lowered. Plants with 30% of the wild‐type PGAM activity in leaves and 55% in tubers showed reduced amounts of starch in tubers also. Tuber‐specific reduction of PGAM expression in transgenic potato plants had no effect on starch metabolism and tuber yield, although the 3‐PGA level was increased. This indicates that 3‐PGA concentrations in potato tubers are not important for regulating ADP‐glucose pyrophosphorylase activity in the production of starch under some environmental conditions.