The Relation of Starch Phosphorylases to Starch Metabolism in Wheat

Abstract

Tissues of wheat (Triticum aestivum L., var. Star) exhibit three starch phosphorylase activity forms resolved by non-denaturing polyacrylamide gel affinity electrophoresis (P1, P2 and P3). Compartmentation analysis of young leaf tissues showed that P3 is plastidic, whereas P1 and P2 are cytosolic. P1 exhibits a strong binding affinity to immobilized glycogen upon electrophoresis, whereas P2 and the chloroplastic P3 do not. Cytosolic leaf phosphorylase was purified to homogeneity by affinity chromatography. The single polypeptide product constituted both the P1 and P2 activity forms. Probes for the detection of phosphorylase transcripts were derived from cDNA sequences of cytosolic and plastidic phosphorylases, and these-together with activity assays and a cytosolic phosphorylase-specific antiserum-were used to monitor phosphorylase expression in leaves and seeds. Mature leaves contained only plastidic phosphorylase, which was also strongly evident in the endosperm of developing seeds at the onset of reserve starch accumulation. Germinating seeds contained only cytosolic phosphorylase, which was restricted to the embryo. Plastidic phosphorylase thus appears to be associated with transitory leaf starch metabolism and with the initiation of seed endosperm reserve starch accumulation, but it plays no role in the degradation of the reserve starch. Cytosolic phosphorylase may be involved in the processing of incoming carbohydrate during rapid tissue growth.

Spatiotemporal Profiling of Starch Biosynthesis and Degradation in the Developing Barley Grain

“…Therefore, the strong expression of PHO1 in barley may also be connected with starch synthesis. Expression of PHO1 in rice (Satoh et al, 2008), wheat (Schupp and Ziegler, 2004), and barley (Fig. 4C) is higher during the early stages of endosperm development, indicating that PHO1 may be essential during early steps of starch synthesis.…”

Mutation of the Plastidial α-Glucan Phosphorylase Gene in Rice Affects the Synthesis and Structure of Starch in the Endosperm

“…Furthermore, there is evidence that disproportionating enzyme (Colleoni et al, 1999;Ball and Morell, 2003) and a-glucan phosphorylase (Schupp and Ziegler, 2004;Dauvillé e et al, 2006) are also involved in this process.…”

“…Two types of starch phosphorylase (Pho) were observed in the following organs of higher plants: spinach (Spinacia oleracea) leaves (Steup and Schä chtele, 1981), pea (Pisum sativum) cotyledons (van Berkel et al, 1991), potato (Solanum tuberosum) leaves (St-Pierre and Brisson, 1995), fava bean (Vicia faba) cotyledons (Buchner et al, 1996), banana (Musa acuminata) fruits (da Mota et al, 2002), and wheat (Triticum aestivum) endosperm (Schupp and Ziegler, 2004). The two Pho types differ from each other not only in structure and kinetic properties but also in their expression pattern and subcellular localization (Steup, 1990).…”

“…Pho1 enzyme activity and protein levels are coordinated with starch production in potato tuber (Kossmann et al, 1991;St-Pierre and Brisson, 1995), maize (Zea mays) endosperm (Ozbun et al, 1973), and wheat endosperm (Schupp and Ziegler, 2004). The exact role of Pho1 in the biosynthesis of polysaccharides in both photosynthetic and nonphotosynthetic tissues of higher plants is still controversial and a subject of many discussions.…”

Variação hormonal correlacionada à expressão de enzimas ligadas ao metabolismo do amido durante o desenvolvimento e amadurecimento da manga (Mangifera indica cv Keitt)

“…Em plantas superiores as amido fosforilases podem ser encontradas em pelo menos duas isoformas sendo uma plastidial (amiloplastos e cloroplastos) e a outra citosólica (SCHUPP et al, 2004).…”