1,721,037 research outputs found
In silico and biochemical analysis of Physcomitrella patens photosynthetic antenna: identification of subunits which evolved upon land adaptation.
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In between algae and plants: analysis of the LHC multigene family of the moss Physcomitrella patens allows identification of light harvesting proteins associated to adaptation to sub-aerial environments
No full textHeat dissipation in the moss Physcomitrella patens: evolution of protection mechanisms upon land colonization
No full textInvited Lectur
HEAT DISSIPATION IN THE MOSS PHYSCOMITRELLA PATENS: LESSONS on MECHANISM and EVOLUTION OF PROTECTION MECHANISMS UPON LAND COLONIZATION
No full textPhotosynthesis regulation in response to fluctuating light in the secondary endosymbiont alga Nannochloropsis gaditana
Full text linkIn nature, photosynthetic organisms are exposed to highly dynamic environmental conditions where the excitation energy and electron flow in the photosynthetic apparatus need to be continuously modulated. Fluctuations in incident light are particularly challenging since they drive oversaturation of photosynthesis, with consequent oxidative stress and photoinhibition. Plants and algae have evolved several mechanisms to modulate their photosynthetic machinery to cope with light dynamics, such as thermal dissipation of excited chlorophyll states (Non-Photochemical Quenching, NPQ) and regulation of electron transport. The regulatory mechanisms involved in the response to light dynamics have adapted during evolution and exploring biodiversity is a valuable strategy for expanding our understanding of their biological roles. In this work, we investigated the response to fluctuating light in Nannochloropsis gaditana, a eukaryotic microalga of the phylum Heterokonta originating from a secondary endosymbiotic event. N. gaditana is negatively affected by light fluctuations, leading to large reductions in growth and photosynthetic electron transport. Exposure to light fluctuations specifically damages photosystem I, likely because of ineffective regulation of electron transport in this species. The role of Non-Photochemical Quenching, also assessed using a mutant strain specifically depleted of this response, was instead found to be minor, especially in responding to the fastest light fluctuations
Photosynthetic response to nitrogen starvation and high light in Haematococcus pluvialis
No full textAstaxanthin is a carotenoid mainly produced by microalgae upon exposure to stress conditions: this pigment has
anti-oxidant, anti-inflammatory and anti-cancer capacity and it is widely used as pigmentation agent in different
industrial sectors. Abiotic stresses such as exposure to high irradiances and/or nitrogen starvation are commonly
used to induce astaxanthin biosynthesis in freshwater green alga Haematococcus pluvialis. In this work high light
and nitrogen deprivation were applied as single or combined stresses in order to investigate their influence on
the photosynthetic properties of H. pluvialis cultures. The results reported here demonstrate that nitrogen
starvation inhibits chlorophyll biosynthesis and favors chlorophyll b degradation, chlororespiration and cyclic
electron transport, while cells grown in high light are characterized by a higher destabilization of PSII. The
combination of high light and nitrogen deprivation induced the highest astaxanthin production and also the
fastest photoprotective response which cooperatively prevented Photosystem II from the damage observed in
high light stress and nitrogen supplemented medium. In these conditions inhibition of astaxanthin accumulation
leads to a reduced cell size but does not induce a higher photosensitivity of photosynthetic machinery
Role of PSBS and LHCSR in Physcomitrella patens acclimation to high light and low temperature
No full textPhotosynthetic organisms respond to strong illumination by activating several photoprotection mechanisms. One of them, non-photochemical quenching (NPQ), consists in the thermal dissipation of energy absorbed in excess. In vascular plants NPQ relies on the activity of PSBS, whereas in the green algae Chlamydomonas reinhardtii it requires a different protein, LHCSR. The moss Physcomitrella patens is the only known organism in which both proteins are present and active in triggering NPQ, making this organism particularly interesting for the characterization of this protection mechanism. We analysed the acclimation of Physcomitrella to high light and low temperature, finding that these conditions induce an increase in NPQ correlated to overexpression of both PSBS and LHCSR. Mutants depleted of PSBS and/or LHCSR showed that modulation of their accumulation indeed determines NPQ amplitude. All mutants with impaired NPQ also showed enhanced photosensitivity when exposed to high light or low temperature, indicating that in this moss the fast-responding NPQ mechanism is also involved in long-term acclimatio
Balancing protection and efficiency in the regulation of photosynthetic electron transport across plant evolution
No full textIn Silico and Biochemical Analysis of Physcomitrella patens Photosynthetic Antenna: Identification of Subunits which Evolved upon Land Adaptation
No full textBackground. In eukaryotes the photosynthetic antenna system is composed of subunits encoded by the light harvesting complex (Lhc) multigene family. These proteins play a key role in photosynthesis and are involved in both light harvesting and photoprotection. The moss Physcomitrella patens is a member of a lineage that diverged from seed plants early after land colonization and therefore by studying this organism, we may gain insight into adaptations to the aerial environment.
Principal Findings. In this study, we characterized the antenna protein multigene family in Physcomitrella patens, by sequence analysis as well as biochemical and functional investigations. Sequence identification and analysis showed that some antenna polypeptides, such as Lhcb3 and Lhcb6, are present only in land organisms, suggesting they play a role in adaptation to the sub-aerial environment. Our functional analysis which showed that photo-protective mechanisms in Physcomitrella patens are very similar to those in seed plants fits with this hypothesis. In particular, Physcomitrella patens also activates Non Photochemical Quenching upon illumination, consistent with the detection of an ortholog of the PsbS protein. As a further adaptation to terrestrial conditions, the content of Photosystem I low energy absorbing chlorophylls also increased, as demonstrated by differences in Lhca3 and Lhca4 polypeptide sequences, in vitro reconstitution experiments and low temperature fluorescence spectra.
Conclusions. This study highlights the role of Lhc family members in environmental adaptation and allowed proteins associated with mechanisms of stress resistance to be identified within this large family
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