A Natural qE- and qZ-Deficient Alga Retains Functional Plant-Like and Chlorophycean Violaxanthin De-Epoxidases
- 1HHMI, University of California
Abstract
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 protothecoides x symbiontica (UTEX 250-A). The Auxenochlorella genome lacks Light-Harvesting Complex Stress Related (LHCSR), one of the two proteins required for the fast energy-dependent quenching (qE) component of NPQ. Mutants lacking the Photosystem II Subunit S (PSBS)-like gene (psbsl1) in Auxenochlorella had no effect on NPQ, indicating this alga lacks canonical qE. We identified two candidate enzymes associated with zeaxanthin-dependent quenching (qZ), which has slower kinetics: a plant-type Violaxanthin De-Epoxidase (VDE) and an algal-type Chlorophycean Violaxanthin De-Epoxidase (CVDE). High light did not trigger the expected conversion of violaxanthin to zeaxanthin, a pigment change that is a hallmark of qZ. Mutants lacking VDE (vde1), CVDE (cvde1), or both enzymes (vde1 cvde1) still displayed slow, reversible NPQ. However, when the Auxenochlorella VDE1 and CVDE1 were expressed in a VDE-deficient mutant of Nicotiana benthamiana, both enzymes restored zeaxanthin production and NPQ, confirming they are catalytically functional de-epoxidases. Together, these results reveal an alga that retains two functional, evolutionarily distinct xanthophyll-cycle enzymes yet does not rely on typical xanthophyll pigment dynamics for photoprotection. This points to a biological function that is decoupled from de-epoxidase activity, highlighting unexplored diversity in green algal photoprotection.
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BibTeX
@misc{cunningham2026natural,
title = {{A Natural qE- and qZ-Deficient Alga Retains Functional Plant-Like and Chlorophycean Violaxanthin De-Epoxidases}},
author = {K. W. Cunningham and S. Wakao and J. L. Hall and C. Blaby-Haas and R. Ivatury and L. Gleeson and D. Chuang and J. J. Kim and J. L. Moseley and G. R. Fleming and K. K. Niyogi},
howpublished = {bioRxiv},
year = {2026},
month = sep,
doi = {10.64898/2026.09.26.754548},
url = {https://www.biorxiv.org/content/10.64898/2026.09.26.754548v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - A Natural qE- and qZ-Deficient Alga Retains Functional Plant-Like and Chlorophycean Violaxanthin De-Epoxidases
AU - K. W. Cunningham
AU - S. Wakao
AU - J. L. Hall
AU - C. Blaby-Haas
AU - R. Ivatury
AU - L. Gleeson
AU - D. Chuang
AU - J. J. Kim
AU - J. L. Moseley
AU - G. R. Fleming
AU - K. K. Niyogi
PY - 2026
DA - 2026/09/26
PB - bioRxiv
DO - 10.64898/2026.09.26.754548
UR - https://www.biorxiv.org/content/10.64898/2026.09.26.754548v1
AB - 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 protothecoides x symbiontica (UTEX 250-A). The Auxenochlorella genome lacks Light-Harvesting Complex Stress Related (LHCSR), one of the two proteins required for the fast energy-dependent quenching (qE) component of NPQ. Mutants lacking the Photosystem II Subunit S (PSBS)-like gene (psbsl1) in Auxenochlorella had no effect on NPQ, indicating this alga lacks canonical qE. We identified two candidate enzymes associated with zeaxanthin-dependent quenching (qZ), which has slower kinetics: a plant-type Violaxanthin De-Epoxidase (VDE) and an algal-type Chlorophycean Violaxanthin De-Epoxidase (CVDE). High light did not trigger the expected conversion of violaxanthin to zeaxanthin, a pigment change that is a hallmark of qZ. Mutants lacking VDE (vde1), CVDE (cvde1), or both enzymes (vde1 cvde1) still displayed slow, reversible NPQ. However, when the Auxenochlorella VDE1 and CVDE1 were expressed in a VDE-deficient mutant of Nicotiana benthamiana, both enzymes restored zeaxanthin production and NPQ, confirming they are catalytically functional de-epoxidases. Together, these results reveal an alga that retains two functional, evolutionarily distinct xanthophyll-cycle enzymes yet does not rely on typical xanthophyll pigment dynamics for photoprotection. This points to a biological function that is decoupled from de-epoxidase activity, highlighting unexplored diversity in green algal photoprotection.
ER -