Mannose and Green Plants: Occurrence, Physiology and Metabolism, and Use as a Tool to Study the Role of Orthophosphate

Observations on the cytoplasmic and vacuolar orthophosphate pools in leaf tissues using in vivo 31P‐NMR spectroscopy

“…Quantitative measurements ( fig.2) emphasize the differential effect of mannose on the two Pi fractions and provide strong support for the assumption that mannose reduces the cytoplasmic Pi in tissues that metabolise mannosed-phosphate slowly [2]. NMR evidence to the contrary from asparagus cells [9] and wheat leaves [7] may reflect shortcomings in the way in which the tissue was handled in the NMR tube.…”

“…A useful experimental approach is to supply the tissue with a readily phosphorylated glucose analogue, such as Dmannose or 2-deoxy-D-glucose, and to exploit the fact that if the subsequent metabolism of the analogue is slow, then the accumulation of mannose 6-phosphate or 2-deoxyglucose 6-phosphate will cause a reduction in the endogenous Pi level [2]. This method has been useful in studies of the partitioning of photosynthate between starch and Abbreviations: MDP, methylene diphosphonic acid; Mes, 2-(Nmorpholino)ethane sulphonic acid; NMR, nuclear magnetic resonance; Pi, orthophosphate; ppm, parts per million; TEMDP, tetraethyl ester of methylene diphosphonic acid sucrose [2,3], and in demonstrating that the supply of Pi to the chloroplast can limit the photosynthetic rate in vivo 141.…”

Arabidopsis Phosphomannose Isomerase 1, but Not Phosphomannose Isomerase 2, Is Essential for Ascorbic Acid Biosynthesis

“…Earlier reports have indicated that PMI was lacking in many plants, and even if it was present, the enzyme activity was very low (29). Additionally, an alternative pathway of GDP-Man and AsA synthesis via a GDP-D-glucose-2-epimerase, which does not involve PMI, GMP, and PMM, has been suggested in higher plants (30).…”

The Barley mlo-gene: an important powdery mildew resistance source

“…However, the effects of DDG, and another glucose analogue mannose [37], may well be indirect since both are known to sequester plant cell phosphate [18,20,38]. Phosphate sequestration would reduce the plant cells potential to synthesise the ATP needed for vital phosphorylation reactions during energy metabolism [23,56]. This would presumably result in lower energy being available for penetration resistance and lead to increased susceptibility.…”