Secondary ketocarotenoid astaxanthin biosynthesis in algae: a multifunctional response to stress

Abstract

Under stressful environments, many green algae such as Haematococcus pluvialis accumulate secondary ketocarotenoids such as canthaxanthin and astaxanthin. The carotenogenesis, responsible for natural phenomena such as red snows, generally accompanies larger metabolic changes as well as morphological modifications, i.e., the conversion of the green flagellated macrozoids into large red cysts. Astaxanthin accumulation constitutes a convenient way to store energy and carbon, which will be used for further synthesis under less stressful conditions. Besides this, the presence of high amount of astaxanthin enhances the cell resistance to oxidative stress generated by unfavorable environmental conditions including excess light, UV-B irradiation, and nutrition stress and, therefore, confers a higher survival capacity to the cells. This better resistance results from the quenching of oxygen atoms for the synthesis itself as well as from the antioxidant properties of the astaxanthin molecules. Therefore, astaxanthin synthesis corresponds to a multifunctional response to stress. In this contribution, the various biochemical, genetic, and molecular data related to the biosynthesis of ketocarotenoids by Haematococcus pluvialis and other taxa are reviewed and compared. A tentative regulatory model of the biochemical network driving astaxanthin production is proposed.

Metabolite Profiling and Integrative Modeling Reveal Metabolic Constraints for Carbon Partitioning under Nitrogen Starvation in the Green Algae Haematococcus pluvialis

“…pluvialis has been extensively investigated due to its ability to produce high amounts of the ketocarotenoid astaxanthin under inductive conditions that are mainly related to stress (8,51). A large amount of research has been conducted to elucidate the astaxanthin biosynthesis pathway and its regulation (for reviews, see Refs.…”

“…1). It is worth mentioning that astaxanthin content makes up a maximum of 4.5% of the biomass (8,51) (Fig. 2A); thus, neither astaxanthin nor total carotenoid content contributes much to the understanding of carbon partitioning in H. pluvialis.…”

Photosynthesis under artificial light: the shift in primary and secondary metabolism

“…They are used in repairing mechanisms [36], shielding [37], reactive oxygen species (ROS) quenching [37] or the production of storage compounds [38]. The synthesis of the metabolites takes place in plastids (terpenoids [38]) or involves them ( phenylpropanoids [32]). Typical examples are medicinal plants and herbs of pharmaceutical importance such as mint (Mentha sp.)…”

Transplastomic plants for innovations in agriculture. A review

“…2). The natural pigment astaxanthin has attracted much attention because of its (1) beneficial effects on human health and importance in the cosmetic industry, (2) importance as animal feed, especially for fish aquacultures such as salmon cultures where it provides the orange color of salmon meat or as human food coloring in the European Union (E161j), and (3) very high market price (Lemoine and Schoefs 2010;Heydarizadeh et al 2013;Ambati et al 2014;Solymosi et al 2015). Astaxanthin is synthesized only by some marine bacteria (e.g., Brevundimonas sp.)…”