A1 Refereed original research article in a scientific journal
Light acclimation in the lycophyte Selaginella martensii depends on changes in the amount of photosystems and on the flexibility of the light-harvesting complex II antenna association with both photosystems
Authors: Lorenzo Ferroni, Marjaana Suorsa, Eva-Mari Aro, Costanza Baldisserotto, Simonetta Pancaldi
Publisher: WILEY-BLACKWELL
Publication year: 2016
Journal: New Phytologist
Journal name in source: NEW PHYTOLOGIST
Journal acronym: NEW PHYTOL
Volume: 211
Issue: 2
First page : 554
Last page: 568
Number of pages: 15
ISSN: 0028-646X
DOI: https://doi.org/10.1111/nph.13939
Abstract
Vascular plants have evolved a long-term light acclimation strategy primarily relying on the regulation of the relative amounts of light-harvesting complex II (LHCII) and of the two photosystems, photosystem I (PSI) and photosystem II (PSII). We investigated whether such a model is also valid in Selaginella martensii, a species belonging to the early diverging group of lycophytes.Selaginella martensii plants were acclimated to three natural light regimes (extremely low light (L), medium light (M) and full sunlight (H)) and thylakoid organization was characterized combining ultrastructural, biochemical and functional methods.From L to H plants, thylakoid architecture was rearranged from (pseudo) lamellar to predominantly granal, the PSII : PSI ratio changed in favour of PSI, and the photochemical capacity increased. However, regulation of light harvesting did not occur through variations in the amount of free LHCII, but rather resulted from the flexibility of the association of free LHCII with PSII and PSI.In lycophytes, the free interspersed LHCII serves a fixed proportion of reaction centres, either PSII or PSI, and the regulation of PSI-LHCII(-PSII) megacomplexes is an integral part of long-term acclimation. Free LHCII ensures photoprotection of PSII, allows regulated use of PSI as an energy quencher, and can also quench endangered PSI.
Vascular plants have evolved a long-term light acclimation strategy primarily relying on the regulation of the relative amounts of light-harvesting complex II (LHCII) and of the two photosystems, photosystem I (PSI) and photosystem II (PSII). We investigated whether such a model is also valid in Selaginella martensii, a species belonging to the early diverging group of lycophytes.Selaginella martensii plants were acclimated to three natural light regimes (extremely low light (L), medium light (M) and full sunlight (H)) and thylakoid organization was characterized combining ultrastructural, biochemical and functional methods.From L to H plants, thylakoid architecture was rearranged from (pseudo) lamellar to predominantly granal, the PSII : PSI ratio changed in favour of PSI, and the photochemical capacity increased. However, regulation of light harvesting did not occur through variations in the amount of free LHCII, but rather resulted from the flexibility of the association of free LHCII with PSII and PSI.In lycophytes, the free interspersed LHCII serves a fixed proportion of reaction centres, either PSII or PSI, and the regulation of PSI-LHCII(-PSII) megacomplexes is an integral part of long-term acclimation. Free LHCII ensures photoprotection of PSII, allows regulated use of PSI as an energy quencher, and can also quench endangered PSI.
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