Feedback control of gene expression

Abstract

Although feedback regulation of photosynthesis by carbon metabolites has long been recognized and investigated, its underlying molecular mechanisms remain unclear. The recent discovery that glucose and acetate trigger global repression of maize photosynthetic gene transcription provides the first direct evidence that a fundamental mechanism is used for feedback regulation of photosynthesis in higher plants. The metabolic repression of photosynthetic genes has now been found in many higher plants and is likely universal. It overrides other regulation by light, tissue type and developmental stage, and serves potentially as the molecular basis of interactions between sink and source tissues. Using simplified and convenient cellular systems and transgenic plants, the study of metabolic regulation of gene expression offers an excellent opportunity for the understanding of global and coordinate gene control and metabolite-mediated signal transduction in higher plants.

Effects of Short- and Long-Term Elevated CO2 on the Expression of Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase Genes and Carbohydrate Accumulation in Leaves of Arabidopsis thaliana (L.) Heynh.1

“…Krapp et al, 1993;Sheen, 1994; have proposed that the increased metabolism of accumulated soluble sugars at high CO 2 may trigger a repression of photosynthetic gene transcription. This repression is thought to be mediated by hexose metabolism via cytosolic hexokinase (Jang and Sheen, 1994;Jang et al, 1997), but we have limited knowledge of the suggested biochemical role of hexokinase as a sugar sensor.…”

“…Sugars are known to influence many metabolic and cellular processes in both prokaryotes and eukaryotes, in part through modulation of gene expression (for reviews, see Sheen, 1994;Saier et al, 1995;Koch, 1996). To date, there is substantial evidence indicating that increased sugar levels can trigger repression of photosynthetic gene transcription.…”

Maize SUT1 functions in phloem loading

“…27,28 In sut1-m1 mutants, photosynthetic and stomatal conductance rates are comparable to wild-type plants only in leaves emerging from the whorl (leaf 7 in Fig. 1E and F), which are in the process of transitioning to source tissue.…”

An Arabidopsis mutant showing reduced feedback inhibition of photosynthesis

“…*Current address: Department of Molecular Genetics, John Innes Centre, Norwich Research Park, Colney, Norwich NR4 7UH, UK. plant (for review see Sheen, 1994;Stitt, 1991). In particular, photosynthesis is inhibited when the production of photosynthates exceeds the rate of utilization by sinks, a sink being an organ which utilizes or stores carbohydrate generated by other parts of the plant.…”