Biology subjects

Morosinotto, T.

Publications and source records attributed to Morosinotto, T..

22 records · Page 2Linked to original sources

bioRxiv2020

The activity of chloroplast NADH dehydrogenase-like complex influences the photosynthetic activity of the moss Physcomitrella patens

Alternative electron pathways contribute to the regulation of photosynthetic light reactions to meet metabolic demands in a dynamic environment. Understanding the molecular mechanisms of their activity is seminal to decipher their role in response to environmental cues and in plant adaptation. The chloroplast NADH dehydrogenase-like (NDH) complex mediates cyclic electron transport pathway around photosystem I (PSI) in different organisms like cyanobacteria, algae and various plant species but has a discontinuous distribution in the green lineage. In order to assess how its activity and physiological role changed during plant evolution, we isolated Physcomitrella patens lines knocked out of the gene NDHM which encodes for a subunit fundamental for the stability and activity of the whole complex. P. patens ndhm KO mosses showed high PSI acceptor side limitation upon illumination leading to PSI photoinhibition. Flavodiiron proteins (FLV) have similar and particularly important role in preventing PSI overreduction when plants are exposed to light fluctuations. The flva ndhm double KO mosses alteration in photosynthetic parameters leaded to a defect in plant growth under fluctuating light as compared to WT and single KO mutants. Results evidenced that, while FLV sustain strong electron transport after an abrupt change in light intensity, NDH contribution to electron transport is small. NDH still participate in modulating PSI activity and it is seminal to prevent PSI photoinhibition especially when FLV are inactive. In plants the functional overlap between NDH- and FLV-dependent electron transport systems sustains PSI activity and to prevent its photoinhibition.

plant biology↗

bioRxiv2019

Regulation of electron transport is essential for photosystem I stability and plant growth

Life depends on the ability of photosynthetic organisms to exploit sunlight to fix carbon dioxide into biomass. Photosynthesis is modulated by pathways such as cyclic and pseudocyclic electron flow (CEF and PCEF). CEF transfers electrons from photosystem I to the plastoquinone pool according to two mechanisms, one dependent on proton gradient regulators (PGR5/PGRL1) and the other on the type I NADH dehydrogenase (NDH) complex. PCEF uses electrons from photosystem I to reduce oxygen; in several groups of photosynthetic organisms but not in angiosperms, it is sustained by flavodiiron proteins (FLVs). PGR5/PGRL1, NDH and FLVs are all active in the moss Physcomitrella patens, and mutants depleted in these proteins show phenotypes under specific light regimes. Here, we demonstrated that CEF and PCEF exhibit strong functional overlap and that when one protein component is depleted, the others can compensate for most of the missing activity. When multiple mechanisms are simultaneously inactivated, however, plants show damage to photosystem I and strong growth reduction, demonstrating that mechanisms for the modulation of photosynthetic electron transport are indispensable.

plant biology↗

bioRxiv2018

Exploration of plant biodiversity to investigate regulation of photosynthesis in natural environment

Photosynthesis is regulated in response to dynamic environmental conditions to satisfy plant metabolic demand but also to avoid over-excitation of the electron transport chain generating harmful reactive oxygen species. Photosynthetic organisms evolved several mechanisms to modulate light harvesting and electron transport efficiency to respond to conditions changing at different timescales, going from fast sun flecks to slow seasonal variations.\n\nThese regulatory mechanisms changed during evolution of photosynthetic organisms, also adapting to various ecological niches. The investigation of plant biodiversity is valuable to uncover conserved traits and plasticity of photosynthetic regulation. In this work a set of plants belonging to different genera of angiosperms, gymnosperms, ferns and lycophytes was investigated by monitoring their photosynthetic parameters in different seasons, looking for common trends and differences. In all plants analysed photosynthetic electron transport rate was found to be modulated by growth light intensity, ensuring a balance between available energy and photochemical capacity. Growth light also influenced the threshold where heat dissipation of excitation energy, also called Non-Photochemical Quenching (NPQ), was activated. On the contrary NPQ amplitude did not correlate with light intensity experienced by the plants but was a species-specific feature.\n\nNPQ zeaxanthin-dependent component, qZ, was found to be the most variable between different plants, modulating the intensity of the response but also the kinetic properties of its activation and relaxation. The slower NPQ component, qI, was instead found to be uncorrelated with photoinhibition eventually suffered by plants.

plant biology↗

bioRxiv2018

Conformational dynamics of a photosynthetic light-harvesting complex in native thylakoid membranes

Photosynthetic light-harvesting complexes of higher plants, moss and green algae can undergo dynamic conformational transitions, which have been correlated to their ability to adapt to fluctuations in the light environment. Herein, we demonstrate the application of solid-state NMR spectroscopy on native, heterogeneous thylakoid membranes of Chlamydomonas reinhardtii (Cr) and on Cr Light-Harvesting Complex II (LHCII) in thylakoid lipid bilayers to detect LHCII conformational dynamics in its native membrane environment. We show that membrane-reconstituted LHCII contains selective sites that undergo fast, large-amplitude motions, including the phytol tails of two chlorophylls. Protein plasticity is also observed in the N-terminal stromal loop and in protein fragments facing the lumen, involving sites that stabilize the xanthophyll-cycle carotenoid violaxanthin and the two luteins. The results report on the intrinsic flexibility of LHCII pigment-protein complexes in a membrane environment, revealing putative sites for conformational switching. In thylakoid membranes, fast dynamics of protein and pigment sites is significantly reduced, which suggests that in their native organelle membranes, LHCII complexes are locked in specific conformational states. STATEMENT OF SIGNIFICANCEPhotosynthetic Light-Harvesting Complexes undergo dynamic conformational transitions that regulate the capacity of the light-harvesting antenna. We demonstrate the application of solid-state (ss)NMR spectroscopy to investigate the structural dynamics of LHCII, the most abundant LHC complex of plants and algae, in native membranes. Selective dynamic protein and pigment residues are identified that are putative sites for a conformational switch.

biophysics↗