The adverse effects of cadmium on plants are accompanied by a limitation of photosynthesis, due to the production of reactive oxygen species, leading to oxidative damage to PSII and the disruption of key protein complexes involved in photosynthetic pathways. We investigated the effects of cadmium stress combined with high light in Arabidopsis thaliana, as dependent on the cadmium dose applied. The aim was to investigate the combined effect of the two stressors on photochemical processes with the hypothesis that Cd stress enhances the negative effect of the high light. The plants were treated with 0, 1, 10, and 50 mM Cd added as CdCl2 solution to soil (potted plants), and a high light stress. The highest dose (50 mM) induced a significant oxidative stress, reduced chlorophyll fluorescence parameters related to PSII functioning and increased energy dissipation mechanisms. Elevated Cd contents impaired the electron transport and limited PSII efficiency. OJIP analysis revealed a Cd-induced K- and L-band appearance documenting LHC-PSII limitation. The combination of Cd and high light stress resulted in the photoinhibition effects in PSII, i.e., a decrease in potential and effective yields of PSII.

• Klíčová slova
• OJIP, cadmium, chlorophyll fluorescence, heavy metal, nonphotochemical quenching, photoinhibition, protective mechanisms,
• MeSH
• Arabidopsis * účinky léků   účinky záření   fyziologie   metabolismus   MeSH
• chlorofyl metabolismus   MeSH
• fotochemické procesy * účinky léků   účinky záření   MeSH
• fotosyntéza * účinky léků   účinky záření   MeSH
• fotosystém II (proteinový komplex) metabolismus   MeSH
• fyziologický stres * účinky léků   MeSH
• kadmium * toxicita   farmakologie   MeSH
• oxidační stres účinky léků   účinky záření   MeSH
• reaktivní formy kyslíku metabolismus   MeSH
• světlo * MeSH
• transport elektronů účinky léků   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• chlorofyl MeSH
• fotosystém II (proteinový komplex) MeSH
• kadmium * MeSH
• reaktivní formy kyslíku MeSH

Photosystem II (PSII) represents the most vulnerable component of the photosynthetic machinery and its response in plants subjected to abiotic stress has been widely studied over many years. PSII is a thylakoid membrane-located multiprotein pigment complex that catalyses the light-induced electron transfer from water to plastoquinone with the concomitant production of oxygen. PSII is rich in intrinsic (PsbA and PsbD, namely D1 and D2, CP47 or PsbB and CP43 or PsbC) but also extrinsic proteins. The first ones are more largely conserved from cyanobacteria to higher plants while the extrinsic proteins are different among species. It has been found that extrinsic proteins involved in oxygen evolution change dramatically the PSII efficiency and PSII repair systems. However, little information is available on the effects of abiotic stress on their function and structure.

• Klíčová slova
• abiotic stress, extrinsic protein, intrinsic protein, photosynthesis, photosystem II,
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

Despite the growing list of identified SARS-CoV-2 receptors, the human angiotensin-converting enzyme 2 (ACE2) is still viewed as the main cell entry receptor mediating SARS-CoV-2 internalization. It has been reported that wild-type mice, like other rodent species of the Muridae family, cannot be infected with SARS-CoV-2 due to differences in their ACE2 receptors. On the other hand, the consensus heparin-binding motif of SARS-CoV-2's spike protein, PRRAR, enables the attachment to rodent heparan sulfate proteoglycans (HSPGs), including syndecans, a transmembrane HSPG family with a well-established role in clathrin- and caveolin-independent endocytosis. As mammalian syndecans possess a relatively conserved structure, we analyzed the cellular uptake of inactivated SARS-CoV-2 particles in in vitro and in vivo mice models. Cellular studies revealed efficient uptake into murine cell lines with established syndecan-4 expression. After intravenous administration, inactivated SARS-CoV-2 was taken up by several organs in vivo and could also be detected in the brain. Internalized by various tissues, inactivated SARS-CoV-2 raised tissue TNF-α levels, especially in the heart, reflecting the onset of inflammation. Our studies on in vitro and in vivo mice models thus shed light on unknown details of SARS-CoV-2 internalization and help broaden the understanding of the molecular interactions of SARS-CoV-2.

• Klíčová slova
• SARS-CoV-2, cellular uptake, heparan sulfate proteoglycans, mouse, syndecans,
• MeSH
• angiotensin-konvertující enzym 2 metabolismus   MeSH
• COVID-19 * metabolismus   virologie   MeSH
• heparansulfát proteoglykany metabolismus   MeSH
• internalizace viru * MeSH
• lidé MeSH
• myši MeSH
• SARS-CoV-2 * metabolismus   MeSH
• savci metabolismus   MeSH
• syndekany metabolismus   MeSH
• tkáňová distribuce * fyziologie   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• angiotensin-konvertující enzym 2 MeSH
• heparansulfát proteoglykany MeSH
• syndekany MeSH

The effects of salt stress condition on the growth, morphology, photosynthetic performance, and paramylon content were examined in the mixotrophic, unicellular, flagellate Euglena gracilis. We found that salt stress negatively influenced cell growth, accompanied by a decrease in chlorophyll (Chl) content. Circular dichroism (CD) spectroscopy revealed the changes in the macro-organization of pigment-protein complexes due to salt treatment, while the small-angle neutron scattering (SANS) investigations suggested a reduction in the thylakoid stacking, an effect confirmed by the transmission electron microscopy (TEM). At the same time, the analysis of the thylakoid membrane complexes using native-polyacrylamide gel electrophoresis (PAGE) revealed no significant change in the composition of supercomplexes of the photosynthetic apparatus. Salt stress did not substantially affect the photosynthetic activity, as reflected by the fact that Chl fluorescence yield, electron transport rate (ETR), and energy transfer between the photosystems did not change considerably in the salt-grown cells. We have observed notable increases in the carotenoid-to-Chl ratio and the accumulation of paramylon in the salt-treated cells. We propose that the accumulation of storage polysaccharides and changes in the pigment composition and thylakoid membrane organization help the adaptation of E. gracilis cells to salt stress and contribute to the maintenance of cellular processes under stress conditions.

• Klíčová slova
• Euglena gracilis, microalgae, paramylon, photosynthesis, salt stress,
• Publikační typ
• časopisecké články MeSH