We explored photoprotective strategies in a cryptophyte alga Rhodomonas salina. This cryptophytic alga represents phototrophs where chlorophyll a/c antennas in thylakoids are combined with additional light-harvesting system formed by phycobiliproteins in the chloroplast lumen. The fastest response to excessive irradiation is induction of non-photochemical quenching (NPQ). The maximal NPQ appears already after 20 s of excessive irradiation. This initial phase of NPQ is sensitive to Ca2+ channel inhibitor (diltiazem) and disappears, also, in the presence of non-actin, an ionophore for monovalent cations. The prolonged exposure to high light of R. salina cells causes photoinhibition of photosystem II (PSII) that can be further enhanced when Ca2+ fluxes are inhibited by diltiazem. The light-induced reduction in PSII photochemical activity is smaller when compared with immotile diatom Phaeodactylum tricornutum. We explain this as a result of their different photoprotective strategies. Besides the protective role of NPQ, the motile R. salina also minimizes high light exposure by increased cell velocity by almost 25% percent (25% from 82 to 104 μm/s). We suggest that motility of algal cells might have a photoprotective role at high light because algal cell rotation around longitudinal axes changes continual irradiation to periodically fluctuating light.

• MeSH
• chlorofyl a metabolismus   MeSH
• chlorofyl metabolismus   MeSH
• Cryptophyta cytologie   metabolismus   účinky záření   MeSH
• fotosystém II (proteinový komplex) metabolismus   MeSH
• pohyb buněk účinky záření   MeSH
• světlo MeSH
• vápník metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• chlorofyl a MeSH
• chlorofyl MeSH
• chlorophyll c MeSH Prohlížeč
• fotosystém II (proteinový komplex) MeSH
• vápník MeSH

It has previously been shown that the long-term treatment of Arabidopsis thaliana with the chloroplast inhibitor lincomycin leads to photosynthetic membranes enriched in antennas, strongly reduced in photosystem II reaction centers (PSII) and with enhanced nonphotochemical quenching (NPQ) (Belgio et al. Biophys J 102:2761-2771, 2012). Here, a similar physiological response was found in the microalga Chromera velia grown under high light (HL). In comparison to cells acclimated to low light, HL cells displayed a severe re-organization of the photosynthetic membrane characterized by (1) a reduction of PSII but similar antenna content; (2) partial uncoupling of antennas from PSII; (3) enhanced NPQ. The decrease in the number of PSII represents a rather unusual acclimation response compared to other phototrophs, where a smaller PSII antenna size is more commonly found under high light. Despite the diminished PSII content, no net damage could be detected on the basis of the Photosynthesis versus irradiance curve and electron transport rates pointing at the excess capacity of PSII. We therefore concluded that the photoinhibition is minimized under high light by a lower PSII content and that cells are protected by NPQ in the antennas.

• Klíčová slova
• Chromera velia alga, High light acclimation, Nonphotochemical quenching, Photoinhibition, Uncoupling of antennas from Photosystem II.,
• MeSH
• aklimatizace účinky záření   MeSH
• Alveolata cytologie   fyziologie   účinky záření   MeSH
• chlorofyl a MeSH
• chlorofyl metabolismus   MeSH
• fluorescence MeSH
• fotochemické procesy účinky záření   MeSH
• fotosyntéza účinky záření   MeSH
• fotosystém II (proteinový komplex) metabolismus   MeSH
• rozpustnost MeSH
• světlo * MeSH
• světlosběrné proteinové komplexy metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• chlorofyl a MeSH
• chlorofyl MeSH
• fotosystém II (proteinový komplex) MeSH
• světlosběrné proteinové komplexy MeSH

Although the chloroplast movement can be strongly affected by ambient temperature, the information about chloroplast movement especially related to high temperatures is scarce. For detailed investigation of the effects of heat stress (HS) on tobacco leaves (Nicotiana tabacum L. cv. Samsun), we used two different HS treatments in dark with wide range of elevated temperatures (25-45 degrees C). The leaf segments were either linearly heated in water bath at heating rate of 2 degrees C min(-1) from room temperature up to maximal temperature (T (m)) and then linearly cooled down to 25 degrees C or incubated for 5 min in water bath at the same T (m) followed by 5 min incubation at 25 degrees C (T-jump). The changes in light-induced chloroplast movement caused by the HS pretreatment were detected after the particular heating regime at 25 degrees C using a method of time-dependent collimated transmittance (CT) and compared with the chlorophyll O-J-I-P fluorescence rise (FLR) measurements. The inhibition of chloroplast movement started at about 40 degrees C while the fluorescence parameters responded generally at higher T (m). This difference in sensitivity of CT and FLR was higher for the T-jump than for the linear HS indicating importance of applied heating regime. A possible influence of chloroplast movement on the FLR measurement and a physiological role of the HS-impaired chloroplast movement are discussed.

• MeSH
• chlorofyl chemie   metabolismus   MeSH
• chloroplasty metabolismus   účinky záření   ultrastruktura   MeSH
• fluorescence MeSH
• fotochemie MeSH
• fotosyntéza fyziologie   MeSH
• fototropismus fyziologie   účinky záření   MeSH
• fyziologický stres fyziologie   MeSH
• listy rostlin cytologie   metabolismus   MeSH
• pohyb buněk fyziologie   účinky záření   MeSH
• světelná stimulace MeSH
• světlo MeSH
• tabák cytologie   metabolismus   účinky záření   MeSH
• teplota MeSH
• vysoká teplota škodlivé účinky   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• srovnávací studie MeSH
• Názvy látek
• chlorofyl MeSH