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Presence of state transitions in the cryptophyte alga Guillardia theta.

Cheregi O, Kotabová E, Prášil O, Schröder WP, Kaňa R, Funk C - J. Exp. Bot. (2015)

Bottom Line: These state transitions were triggered by blue light absorbed by the membrane integrated chlorophyll a/c antennae, and green light absorbed by the lumenal biliproteins was ineffective.It is proposed that state transitions in G. theta are induced by small re-arrangements of the intrinsic antennae proteins, resulting in their coupling/uncoupling to the photosystems in state 1 or state 2, respectively.G. theta therefore represents a chromalveolate algae able to perform state transitions.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Umeå University, SE-90187 Umeå, Sweden.

No MeSH data available.


Related in: MedlinePlus

State-transition-like behavior of G. theta cells in dependence to the culture age. (A) Changes in maximal fluorescence during dark/light/dark transition. G. theta cells were dark adapted for 20min to measure the Fm1 value, and then exposed to low blue light (see blue bar) to receive the Fm2 value. Reversibility of this process was confirmed by a second dark period (black bar starting at 350 s). B. Difference in variable fluorescence Fv in samples exposed to low white light (2.5 µmol photons m−2 s−1) or dark adapted at different time points. Fv was normalized to the density of the culture with the help of the minimal fluorescence value F0; ΔFv/F0 was calculated as Fv(LL)/F0(LL)−Fv(D)/F0(D).
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Figure 6: State-transition-like behavior of G. theta cells in dependence to the culture age. (A) Changes in maximal fluorescence during dark/light/dark transition. G. theta cells were dark adapted for 20min to measure the Fm1 value, and then exposed to low blue light (see blue bar) to receive the Fm2 value. Reversibility of this process was confirmed by a second dark period (black bar starting at 350 s). B. Difference in variable fluorescence Fv in samples exposed to low white light (2.5 µmol photons m−2 s−1) or dark adapted at different time points. Fv was normalized to the density of the culture with the help of the minimal fluorescence value F0; ΔFv/F0 was calculated as Fv(LL)/F0(LL)−Fv(D)/F0(D).

Mentions: Detailed analysis of NPQ in G. theta cultures was performed with respect to the culture age (Fig. 5B). Surprisingly, in the logarithmic phase, G. theta cells showed rather low NPQ (below 0.5, see Fig. 5A, Day 2), while in the stationary phase NPQ steadily increased (Fig. 5A, Day 13). These results are in contrast to NPQ measurements performed in R. salina, which displayed quite high NPQ values (~1.4 at Day 2, see Supplementary Fig. S1, available at JXB online) already in very young cultures. Further, the presence of state transition was quantified in G. theta at different culture ages. During logarithmic growth phase, characterized by low NPQ, a phenomenon similar to state-transitions was detected in G. theta cells (Fig. 6A); pretreatment with low-light (2 µmol photons m−2 s−1) was required to reach maximal fluorescence. When dark-adapted G. theta cells were exposed to low-intensity blue light (7 µmol photons m−2 s−1 for 300 s) the fluorescence increased, this process was reversed in darkness (Fig. 6A). This dark recovery was also observed during treatment with saturating blue flashes (see red curve in Fig. 6A), therefore it was independent of fluorescence quenching. Instead, the initial fluorescence increase, Fm, in low blue light, was attributed to state 2 to state 1 transition; the following decrease in darkness then corresponded to state 1 to state 2 transition. State 2 to state 1 transitions were observed in G. theta only after exposure to low-intensity blue light, green light had no effect, neither on state 2 to state 1 transition nor on its recovery (see Supplementary Fig. 2A, 2B). Thus, state transitions in G. theta are exclusively controlled by chlorophyll-binding proteins and not by the lumen-located phycoerythrin antenna. Room temperature fluorescence emission spectra were recorded on dark-adapted cells either exposed to blue light for 5min or kept in darkness (Fig. 7). Dark-adapted cells had a substantially lower maximal variable fluorescence (Fm) (see Fm1 in Fig. 7A). The difference spectra between Fm1 in State 2 and Fm2 in State 1 (Fig. 7B) displays a pronounced increase of chlorophyll a emission in Fm2 originating from PSII. Interesting to note, state transitions were only observed in G. theta cultures in the logarithmic growth phase (Figs 6A, B and 7 and Supplementary Fig. S2); while these low light-induced changes in variable fluorescence disappeared in the stationary phase (after Day 6, see ΔFv/F0 in Fig. 6B), NPQ increased (Fig. 5B).


Presence of state transitions in the cryptophyte alga Guillardia theta.

Cheregi O, Kotabová E, Prášil O, Schröder WP, Kaňa R, Funk C - J. Exp. Bot. (2015)

State-transition-like behavior of G. theta cells in dependence to the culture age. (A) Changes in maximal fluorescence during dark/light/dark transition. G. theta cells were dark adapted for 20min to measure the Fm1 value, and then exposed to low blue light (see blue bar) to receive the Fm2 value. Reversibility of this process was confirmed by a second dark period (black bar starting at 350 s). B. Difference in variable fluorescence Fv in samples exposed to low white light (2.5 µmol photons m−2 s−1) or dark adapted at different time points. Fv was normalized to the density of the culture with the help of the minimal fluorescence value F0; ΔFv/F0 was calculated as Fv(LL)/F0(LL)−Fv(D)/F0(D).
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Figure 6: State-transition-like behavior of G. theta cells in dependence to the culture age. (A) Changes in maximal fluorescence during dark/light/dark transition. G. theta cells were dark adapted for 20min to measure the Fm1 value, and then exposed to low blue light (see blue bar) to receive the Fm2 value. Reversibility of this process was confirmed by a second dark period (black bar starting at 350 s). B. Difference in variable fluorescence Fv in samples exposed to low white light (2.5 µmol photons m−2 s−1) or dark adapted at different time points. Fv was normalized to the density of the culture with the help of the minimal fluorescence value F0; ΔFv/F0 was calculated as Fv(LL)/F0(LL)−Fv(D)/F0(D).
Mentions: Detailed analysis of NPQ in G. theta cultures was performed with respect to the culture age (Fig. 5B). Surprisingly, in the logarithmic phase, G. theta cells showed rather low NPQ (below 0.5, see Fig. 5A, Day 2), while in the stationary phase NPQ steadily increased (Fig. 5A, Day 13). These results are in contrast to NPQ measurements performed in R. salina, which displayed quite high NPQ values (~1.4 at Day 2, see Supplementary Fig. S1, available at JXB online) already in very young cultures. Further, the presence of state transition was quantified in G. theta at different culture ages. During logarithmic growth phase, characterized by low NPQ, a phenomenon similar to state-transitions was detected in G. theta cells (Fig. 6A); pretreatment with low-light (2 µmol photons m−2 s−1) was required to reach maximal fluorescence. When dark-adapted G. theta cells were exposed to low-intensity blue light (7 µmol photons m−2 s−1 for 300 s) the fluorescence increased, this process was reversed in darkness (Fig. 6A). This dark recovery was also observed during treatment with saturating blue flashes (see red curve in Fig. 6A), therefore it was independent of fluorescence quenching. Instead, the initial fluorescence increase, Fm, in low blue light, was attributed to state 2 to state 1 transition; the following decrease in darkness then corresponded to state 1 to state 2 transition. State 2 to state 1 transitions were observed in G. theta only after exposure to low-intensity blue light, green light had no effect, neither on state 2 to state 1 transition nor on its recovery (see Supplementary Fig. 2A, 2B). Thus, state transitions in G. theta are exclusively controlled by chlorophyll-binding proteins and not by the lumen-located phycoerythrin antenna. Room temperature fluorescence emission spectra were recorded on dark-adapted cells either exposed to blue light for 5min or kept in darkness (Fig. 7). Dark-adapted cells had a substantially lower maximal variable fluorescence (Fm) (see Fm1 in Fig. 7A). The difference spectra between Fm1 in State 2 and Fm2 in State 1 (Fig. 7B) displays a pronounced increase of chlorophyll a emission in Fm2 originating from PSII. Interesting to note, state transitions were only observed in G. theta cultures in the logarithmic growth phase (Figs 6A, B and 7 and Supplementary Fig. S2); while these low light-induced changes in variable fluorescence disappeared in the stationary phase (after Day 6, see ΔFv/F0 in Fig. 6B), NPQ increased (Fig. 5B).

Bottom Line: These state transitions were triggered by blue light absorbed by the membrane integrated chlorophyll a/c antennae, and green light absorbed by the lumenal biliproteins was ineffective.It is proposed that state transitions in G. theta are induced by small re-arrangements of the intrinsic antennae proteins, resulting in their coupling/uncoupling to the photosystems in state 1 or state 2, respectively.G. theta therefore represents a chromalveolate algae able to perform state transitions.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Umeå University, SE-90187 Umeå, Sweden.

No MeSH data available.


Related in: MedlinePlus