Physiology of starch storage in the monocellular alga Chlamydomonas reinhardtii

• Published in: Plant science (Limerick) Vol. 66; no. 1; pp. 1 - 9
• Main Authors: Ball, Steven G, Dirick, Leon, Decq, André, Martiat, Jean-Claude, Matagne, René F.
• Format: Journal Article
• Language: English
• Published: Elsevier 1989
• Subjects: Life Sciences; Vegetal Biology
• ISSN: 0168-9452; 1873-2259

Glycogen accumulation in nutrient starved or stationary phase cells has been described as a widespread phenomenon both in bacteria and yeasts [1; for a review see Ref. 2]. Carbohydrate accumulation in phototrophically grown phosphate starved algae [3] and starch synthesis in nitrogen depleted Chlamydomonas reinhardtii cells grown in a light and dark cycle have been reported [4]. In yeast glycogen synthesis and degradation seems to be regulated by cell cycle dependent protein pbosphorylation in a somewhat reminiscent fashion to the situation described for higher animals [5- 7]. In plants little is known by comparison about the regulation of starch synthesis [8; for a review see Ref. 9]. Indeed, the compartmentation of starch in the chloroplast could reveal very different control mechanisms with respect to what is known about cytosolic glycogen. To study this regulation we have investigated the response of the unicellular green alga C. reinhardtii to nutrient starvation. In this report, we show that C. reinhardtii accumulates large amounts of starch, when growth is restricted, in limiting CO 2 conditions in the light or from acetate in the dark. This response mimicks starch accumulation in leaves or non-photosynthetic storage organs in higher plants. Starch accumulation in C. reinhardtii seems to be solely under nuclear genetic control and can be correlated with changes in enzyme activities associated with starch metabolism.