Regulation of photosynthesis in heterokont algae

Abstract

Several microalgae belonging to the phylum of Heterokontophyta have recently been studied with increasing interest, as these microalgae are able to produce very high amounts of fatty acids which are both interesting for biodiesel production and in a nutritional perspective. The production of these fatty acids depends on photosynthesis, which fuels the uptake of inorganic carbon. Their photosynthetic processes have, however, not been studied as extensively as their ability to produce lipids.

The work underlying this thesis has been focusing on the regulation of photosynthetic electron transport in heterokont algae, and also on how the different processes involved in photosynthesis affect the algae’s ability to fix inorganic carbon and thus be efficient lipid producers.

The work has focused on the microalgae Nannochloropsis oceanica and Phaeodactylum tricornutum, and it has been determined that photosynthesis is differently regulated in these algae compared to in green algae and higher plants.

First of all, high light, which is known to reduce the photosynthetic electron transport chain in green algae and plants, have been shown to have the opposite effect in N. oceanica and P. tricornutum. And since several spectroscopic techniques aimed at investigating different aspects of photosynthesis are based on the assumption that high light reduces the electron transport chain, this might lead to misinterpretations of data obtained using such techniques.

It has also been determined that heterokont algae, in contrast to what was previously thought, most likely use state transitions as a mode of photoprotection in conditions where their photosystems are in need of protection.