DAN fluorescence could not be detected by this method but the oxidative burst caused by c-PTIO provided indirect ACY-738 molecular weight evidence of endogenous NO production in the algae. Direct measurements of NO end-products in the supernatant of photobiont suspensions at different time periods of culture (0-24 h) showed that these algae were able to produce NO in the low-nanogram range. NO levels reached a peak of 567 ng per million cells 2 h after preparation of the suspension (Table 1). Figure 6 ROS content of isolated Trebouxia sp. Capital letters MK-8931 chemical structure identify the fluorescence
image; the lower-case letter indicates the corresponding bright-field images: A-a control; B-b algae treated with 200 μM c-PTIO. Each micrograph is representative of several images corresponding to independent samples. Magnification 1000×. Bar 20 μm Table 1 NO end-products of the Trebouxia sp. photobiont isolated from Ramalina farinacea at different time
points after the establishment of the algal suspension Time (h) ng NOx/106 cells ± standard error (n = 9) 0 3.87 ± 0.378 1 3.49 ± 0.418 2 567 ± 282 4 3.17 ± 0.461 24 3.06 ± 0.414 Photosynthetic studies on isolated algae To confirm that the visualized alterations in chlorophyll fluorescence were linked to alterations in the photosynthetic activity of the algae during NO deprivation, axenic cultures of Asterochloris erici, a well-characterized photobiont, were studied. The cells were cultured on cellulose-acetate discs, desiccated for 24 h, and rehydrated with 200 μM c-PTIO. Measurements were made in cells that 4SC-202 concentration had been maintained in culture conditions for 24 h. The significant decrease of Fv/Fm and ФPSII indicated that NO scavenging induces photo-inhibition of PSII (Figure 7). The degree of quinone A (QA) oxidation was determined as qP, which depends on the activation state of photosystem I (PSI) and the Calvin cycle . After the dehydration/rehydration cycle, no differences were observed in qP, indicating that photoinhibition was produced before QA. Figure 7 Effect of NO inhibition in Asterochloris erici photosynthetic parameters. Photosynthetic parameters of axenic cultures of Asterochloris erici
desiccated for 24 h and then rehydrated with either deionized water or 200 μM c-PTIO. The algae were incubated under normal culture conditions for 24 h before chlorophyll a fluorescence was measured. Control algae were not desiccated BCKDHA but instead maintained under normal culture conditions. Fv/Fm, maximum photochemical efficiency of photosystem II (PSII); ФPSII, photochemical efficiency in light; qP, photochemical component of fluorescence relaxation. Different letters show significant differences between treatments. LSD test (p < 0.05), n = 3 The same treatments and measurements were carried out in whole thalli of R. farinacea but no alterations in photosynthesis at 24 h were observed (data not shown). Discussion This study investigated the role of NO during rehydration in Ramalina farinacea.