Deactivation of Photosynthetic Activities is Triggered by Loss of a Small Amount of Water in a Desiccation-Tolerant Cyanobacterium, Nostoc commune

Abstract

Changes in photosynthetic activities under hypertonic conditions were studied in a terrestrial, highly desiccation-tolerant cyanobacterium, Nostoc commune, and in some desiccation-sensitive cyanobacteria. The amounts of water sustained in the colony matrix outside the N. commune cells and the cellular solute concentration were estimated by measuring the water potential, and the solute concentration was supposed to correspond to around 0.22 M sorbitol. Incubation of the colonies in 0.8 M sorbitol solution inhibited the energy transfer from the phycobilisome (PBS) anchor to PSII core complexes. At higher sorbitol concentrations, light energy absorbed by PSI, PSII, and PBS was dissipated to heat. PSI and cyclic electron flow around PSI was also deactivated by hypertonic treatment. Fv/Fm and (Fm'-F)/Fm' values started to decrease at 0.6 and 0.3 M sorbitol and reached zero at 1.0 and 0.8 M, respectively. Decreases in these two fluorescence parameters corresponded to the decreases in PSII fluorescence (F695) and photosynthetic CO2 fixation, respectively. The intensity of delayed light emission started to decrease at 1.0 M sorbitol and became negligible at 4.0 M. Comparing these changes in N. commune with those in desiccation-sensitive species, we found that N. commune cells actively deactivates photosynthetic systems on sensing water loss.

Ideal Osmotic Spaces for Chlorobionts or Cyanobionts Are Differentially Realized by Lichenized Fungi

“…h Data from a previous report (Satoh et al, 2002). Data from a previous report (Hirai et al, 2004). activity and photosynthetic electron flow of the cyanolichen C. subflaccidum were observed (Fig.…”

“…An increase in compatible solutes prevents water loss or increases water uptake from the air when humidity is high (Lange et al, 1988). It has been observed, however, that the intracellular solute concentration is low (corresponding to a sorbitol concentration of approximately 0.22 M) in the desiccation-tolerant terrestrial cyanobacterium Nostoc commune (Satoh et al, 2002;Hirai et al, 2004). N. commune photosynthetic activity is lost when incubated in low sorbitol concentrations (Hirai et al, 2004), whereas a Trebouxia spp.…”

“…It has been observed, however, that the intracellular solute concentration is low (corresponding to a sorbitol concentration of approximately 0.22 M) in the desiccation-tolerant terrestrial cyanobacterium Nostoc commune (Satoh et al, 2002;Hirai et al, 2004). N. commune photosynthetic activity is lost when incubated in low sorbitol concentrations (Hirai et al, 2004), whereas a Trebouxia spp. chlorobiont freshly isolated from the desiccation-tolerant chlorolichen Ramalina yasudae remains active under the same conditions (Kosugi et al, 2009).…”

Relationship of cyanobacterial and algal assemblages with vegetation in the high Arctic tundra (West Spitsbergen, Svalbard Archipelago)

“…Its thalli covered up to 50% of uncovered, moist soil in the analyzed habitats. In polar regions N. commune may occur in a water environment in associ− ation with mosses, but, above all, it is an obligatory taxon for surface habitats (Howard−Williams et al 1986;Fumanti et al 1995;Hirai et al 2004, Fukunda et al 2008, Komárek J. and Elster 2008Komárek O. and Komárek J. 2010).…”

Responses of photosynthetic activity in the drought-tolerant cyanobacterium, Nostoc flagelliforme to rehydration at different temperature

“…Qian et al (1989) have reported that the recovery of photosynthesis occurs mainly during the rainy season in which the recovered photosynthesis provides compounds and energy for the growth and reproduction of N. flagelliforme. Many studies on the photosynthetic function of Nostoc commune in response to dehydration and rehydration have been performed (Hirai et al, 2004;Satoh et al, 2002), but the rate of photosynthesis recovery in N. flagelliforme was shown to be more rapid than that in N. commune (Scherer et al, 1984). Previous studies showed that the photosynthetic resumption of N. flagelliforme not only depended on light, potassium, and water (Gao et al, 1998b;Huang et al, 2005;Qiu and Gao, 1999), but also required de novo protein synthesis (Qiu et al, 2004).…”