Photoprotection in a monophyletic branch of chlorophyte algae is independent of energy-dependent quenching (qE).
Phototrophic organisms need to ensure high photosynthetic performance whilst suppressing reactive oxygen species (ROS)-induced stress occurring under excess light conditions. The xanthophyll cycle (XC), related to the high-energy quenching component (qE) of the nonphotochemical quenching (NPQ) of excitation energy, is considered to be an obligatory component of photoprotective mechanisms. The pigment composition of at least one representative of each major clade of Ulvophyceae (Chlorophyta) was investigated. We searched for a light-dependent conversion of pigments and investigated the NPQ capacity with regard to the contribution of XC and the qE component when grown under different light conditions. A XC was found to be absent in a monophyletic group of Ulvophyceae, the Bryopsidales, when cultivated under low light, but was triggered in one of the 10 investigated bryopsidalean species, Caulerpa cf. taxifolia, when cultivated under high light. Although Bryopsidales accumulate zeaxanthin (Zea) under high-light (HL) conditions, NPQ formation is independent of a XC and not related to qE. qE- and XC-independent NPQ in the Bryopsidales contradicts the common perception regarding its ubiquitous occurrence in Chloroplastida. Zea accumulation in HL-acclimated Bryopsidales most probably represents a remnant of a functional XC. The existence of a monophyletic algal taxon that lacks qE highlights the need for broad biodiversity studies on photoprotective mechanisms.
Molecular Evolution, Heinrich-Heine-University Düsseldorf, 40225, Düsseldorf, Germany.|Department of Biology and CESAM, University of Aveiro, 3810-193, Aveiro, Portugal.
Gregor
G
Christa
Department of Biology and CESAM, University of Aveiro, 3810-193, Aveiro, Portugal.
Sónia
S
Cruz
Plant Biochemistry and Stress Physiology, Heinrich-Heine-University Düsseldorf, 40225, Düsseldorf, Germany.
Peter
P
Jahns
Molecular Evolution, Heinrich-Heine-University Düsseldorf, 40225, Düsseldorf, Germany.|Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS, B3H 4R2, Canada.
Jan
http://orcid.org/0000-0003-3507-5195
J
de Vries
Department of Biology and CESAM, University of Aveiro, 3810-193, Aveiro, Portugal.
Paulo
P
Cartaxana
Department of Biology and CESAM, University of Aveiro, 3810-193, Aveiro, Portugal.
Ana Cristina
AC
Esteves
Department of Biology and CESAM, University of Aveiro, 3810-193, Aveiro, Portugal.
João
J
Serôdio
Molecular Evolution, Heinrich-Heine-University Düsseldorf, 40225, Düsseldorf, Germany.
Sven B
SB
Gould
D000460:Chlorophyta / Q000254:growth & development / Q000502:physiology* / Q000528:radiation effects; D003624:Darkness; D008027:Light; D055668:Photochemical Processes; D010802:Phylogeny; D013312:Stress, Physiological / Q000528:radiation effects; D013816:Thermodynamics; D024341:Xanthophylls / Q000378:metabolism; D065146:Zeaxanthins
D024341:Xanthophylls; D065146:Zeaxanthins
Chlorophyta; nonphotochemical quenching (NPQ); photoprotection; photosynthetic pigments; stress physiology; xanthophyll cycle (XC)