Effects of granule-bound starch synthase I-defective mutation on the morphology and structure of pyrenoidal starch in Chlamydomonas.

Lowering of the CO₂ concentration in the environment induces development of a pyrenoidal starch sheath, as well as that of pyrenoid and CO₂-concentrating mechanisms, in many microalgae. In the green algae Chlamydomonas and Chlorella, activity of granule-bound starch synthase (GBSS) concomitantly increases under these conditions. In this study, effects of the GBSS-defective mutation (sta2) on the development of pyrenoidal starch were investigated in Chlamydomonas.

The primitive rhodophyte Cyanidioschyzon merolae contains a semiamylopectin-type, but not an amylose-type, alpha-glucan.

The storage glucans of Cyanidioschyzon merolae [clade L-1 (cyanidian algae), order Porphyridiales, subclass Bangiophycidae], which is considered to be one of the most primitive rhodophytes, were analyzed to understand the early evolution of the glucan structure in the Rhodophyta. Chain-length distribution analysis of the glucans of cyanidian algae demonstrated that while the glucans of Cyanidium caldarium and Galdieria sulphuraria are of the glycogen type, those of C. merolae are of the semiamylopectin type, as in other lineages of the Rhodophyta.

Variation in storage alpha-polyglucans of red algae: amylose and semi-amylopectin types in Porphyridium and glycogen type in Cyanidium.

Red algae are widely known to produce floridean starch but it remains unclear whether the molecular structure of this algal polyglucan is distinct from that of the starch synthesized by vascular plants and green algae. The present study shows that the unicellular species Porphyridium purpureum R-1 (order Porphyridiales, class Bangiophyceae) produces both amylopectin-type and amylose-type alpha-polyglucans. In contrast, Cyanidium caldarium (order Porphyridiales, class Bangiophyceae) synthesizes glycogen-type polyglucan, but not amylose.

Granule-bound starch synthase cDNA in Chlorella kessleri 11 h: cloning and regulation of expression by CO(2) concentration.

The cDNA for the granule-bound starch synthase (GBSS; ADP-glucose-starch glucosyltransferase, EC 2.4.1.