A Natural qE- and qZ-Deficient Alga Retains Functional Plant-Like and Chlorophycean Violaxanthin De-Epoxidases
Photosynthetic organisms protect themselves from excess light through non-photochemical quenching (NPQ), a process that safely dissipates excess light energy as heat. Current understanding of NPQ is largely drawn from a few model systems, leaving it unclear how universal NPQ mechanisms are across the green lineage. We characterize the slow, sustained NPQ of the green alga, Auxenochlorella…
In the green alga Auxenochlorella protothecoides x symbiontica (UTEX 250-A), researchers discovered two functional enzymes, Violaxanthin De-Epoxidase (VDE) and Chlorophycean Violaxanthin De-Epoxidase (CVDE), that are responsible for zeaxanthin-dependent quenching (qZ). This process is slower than the more commonly studied fast energy-dependent quenching (qE).
Interestingly, despite lacking the Light-Harvesting Complex Stress Related (LHCSR) protein, which is necessary for qE, the alga still exhibits slow, reversible NPQ. When the VDE and CVDE enzymes were introduced into a VDE-deficient plant, they restored zeaxanthin production and NPQ, confirming their catalytic function. This finding suggests that this alga possesses a unique form of photoprotection that is distinct from the typical xanthophyll cycle dynamics found in other green plants and algae.
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