Sucrose Synthase and Fructokinase Are Required for Proper Meristematic and Vascular Development.

Sucrose synthase (SuSy) and fructokinase (FRK) work together to control carbohydrate flux in sink tissues. SuSy cleaves sucrose into fructose and UDP-glucose; whereas FRK phosphorylates fructose. Previous results have shown that suppression of the genes by SUS-RNAi alters auxin transport in the shoot apical meristems of tomato plants and affects cotyledons and leaf structure; whereas antisense suppression of affects vascular development.

Guard cells control hypocotyl elongation through HXK1, HY5, and PIF4.

The hypocotyls of germinating seedlings elongate in a search for light to enable autotrophic sugar production. Upon exposure to light, photoreceptors that are activated by blue and red light halt elongation by preventing the degradation of the hypocotyl-elongation inhibitor HY5 and by inhibiting the activity of the elongation-promoting transcription factors PIFs. The question of how sugar affects hypocotyl elongation and which cell types stimulate and stop that elongation remains unresolved.

An Overview of Sucrose Synthases in Plants.

Sucrose is the end product of photosynthesis and the primary sugar transported in the phloem of most plants. Sucrose synthase (SuSy) is a glycosyl transferase enzyme that plays a key role in sugar metabolism, primarily in sink tissues. SuSy catalyzes the reversible cleavage of sucrose into fructose and either uridine diphosphate glucose (UDP-G) or adenosine diphosphate glucose (ADP-G).

Plant Fructokinases: Evolutionary, Developmental, and Metabolic Aspects in Sink Tissues.

Sucrose, a glucose-fructose disaccharide, is the main sugar transported in the phloem of most plants and is the origin of most of the organic matter. Upon arrival in sink tissues, the sucrose must be cleaved by invertase or sucrose synthase. Both sucrose-cleaving enzymes yield free fructose, which must be phosphorylated by either fructokinase (FRK) or hexokinase (HXK).

Suppression of sucrose synthase affects auxin signaling and leaf morphology in tomato.

Metabolic enzymes have been found to play roles in plant development. Sucrose synthase (SUS) is one of the two enzyme families involved in sucrose cleavage in plants. In tomato, six SUS genes have been found.

Corrigendum: Arabidopsis Fructokinases Are Important for Seed Oil Accumulation and Vascular Development.

[This corrects the article on p. 2047 in vol. 7, PMID: 28119723.

Arabidopsis Fructokinases Are Important for Seed Oil Accumulation and Vascular Development.

Sucrose (a disaccharide made of glucose and fructose) is the primary carbon source transported to sink organs in many plants. Since fructose accounts for half of the hexoses used for metabolism in sink tissues, plant fructokinases (FRKs), the main fructose-phosphorylating enzymes, are likely to play a central role in plant development. However, to date, their specific functions have been the subject of only limited study.

The tomato plastidic fructokinase SlFRK3 plays a role in xylem development.

Plants have two kinds of fructokinases (FRKs) that catalyze the key step of fructose phosphorylation, cytosolic and plastidic. The major cytosolic tomato FRK, SlFRK2, is essential for the development of xylem vessels. In order to study the role of SlFRK3, which encodes the only plastidic FRK, we generated transgenic tomato (Solanum lycopersicon) plants with RNAi suppression of SlFRK3 as well as plants expressing beta-glucoronidase (GUS) under the SlFRK3 promoter.

Substantial roles of hexokinase and fructokinase in the effects of sugars on plant physiology and development.

The basic requirements for plant growth are light, CO2, water, and minerals. However, the absorption and utilization of each of these requires investment on the part of the plant. The primary products of plants are sugars, and the hexose sugars glucose and fructose are the raw material for most of the metabolic pathways and organic matter in plants.