Slow zeaxanthin accumulation and the enhancement of CP 26 collectively contribute to an atypical non‐photochemical quenching in macroalga Ulva prolifera under high light

• Published in: Journal of phycology 2020-04, Vol.56 (2), p.393-403
• Main Authors: Gao, Shan, Zheng, Zhenbing, Wang, Jing, Wang, Guangce
• Format: Article
• Language: English
• ISSN: 0022-3646; 1529-8817
• DOI: 10.1111/jpy.12958

Non‐photochemical quenching ( NPQ ) is an important photoprotective mechanism in plants, which dissipates excess energy and further protects the photosynthetic apparatus under high light stress. NPQ can be dissected into a number of components: qE , qZ , and qI . In general, NPQ is catalyzed by two independent mechanisms, with the faster‐activated quenching catalyzed by the monomeric light‐harvesting complex ( LHCII ) proteins and the slowly activated quenching catalyzed by LHCII trimers, both processes depending on zeaxanthin but to different extent. Here, we studied the NPQ of the intertidal green macroalga, Ulva prolifera , and found that the NPQ of U. prolifera lack the faster‐activated quenching, and showed much greater sensitivity to dithiothreitol ( DTT ) than to dicyclohexylcarbodiimide ( DCCD ). Further results suggested that the monomeric LHC proteins in U. prolifera included only CP 29 and CP 26, but lacked CP 24, unlike Arabidopsis thaliana and the moss Physcomitrella patens . Moreover, the expression levels of CP 26 increased significantly following exposure to high light, but the concentrations of the two important photoprotective proteins (PsbS and light‐harvesting complex stress‐related [Lhc SR ]) did not change upon the same conditions. Analysis of the xanthophyll cycle pigments showed that, upon exposure to high light, zeaxanthin synthesis in U. prolifera was gradual and much slower than that in P. patens , and could effectively be inhibited by DTT . Based on these results, we speculate the enhancement of CP 26 and slow zeaxanthin accumulation provide an atypical NPQ , making this green macroalga well adapted to the intertidal environments.