Role of calcium in the mitigation of heat stress in the cyanobacterium Anabaena PCC 7120.
The effects of exogenously added CaCl2(0.25mM) on photopigments, photosynthetic O2-evolution, antioxidative enzyme activity, membrane damage, expression of two heat shock genes (groEL and groES) and apoptotic features in Anabaena 7120 under heat stress (45°C) for up to 24h were investigated. Heat stress lowered the level of photopigments; however, Ca2+--supplemented cultures showed a low level reduction in Chl a but induced accumulation of carotenoids and phycocyanin under heat stress. Photosynthetic O2-evolving capacity was maintained at a higher level in cells from Ca2+-supplemented medium. Among the antioxidative enzymes, superoxide dismutase activity was unaffected by the presence or absence of Ca2+in contrast to increases in catalase, ascorbate peroxidase and glutathione reductase activities in cells grown in Ca2+-supplemented medium. Lower levels of lipid peroxidation were recorded in Anabaena cells grown in Ca2+-supplemented medium in comparison to cells from Ca2+--deprived medium. Target cells grown in Ca2+-deprived medium developed apoptotic features in the early stages of heat shock, while Ca2+application seemed to interfere with apoptosis because only a few cells showed such features after 24 h of heat exposure, indicating a role for Ca2+in maintaining cell viability under heat stress. There was also continuous up regulation of two important heat shock genes (groEL and groES) in Ca2+-supplemented cultures, exposed to heat shock, again indicating a role for Ca2+in stress management.
R.N. Singh Memorial Lab, Centre of Advanced study in Botany, Banaras Hindu University, Varanasi 221005, India.
Anupam
A
Tiwari
R.N. Singh Memorial Lab, Centre of Advanced study in Botany, Banaras Hindu University, Varanasi 221005, India.
Priyanka
P
Singh
R.N. Singh Memorial Lab, Centre of Advanced study in Botany, Banaras Hindu University, Varanasi 221005, India. Electronic address: asthana.ravi@gmail.com.
Ravi Kumar
RK
Asthana
D017033:Anabaena / Q000187:drug effects* / Q000235:genetics / Q000502:physiology; D000975:Antioxidants / Q000378:metabolism*; D017209:Apoptosis / Q000187:drug effects; D001426:Bacterial Proteins / Q000235:genetics; D002122:Calcium Chloride / Q000494:pharmacology*; D002338:Carotenoids / Q000378:metabolism; D018835:Chaperonin 10 / Q000235:genetics; D018834:Chaperonin 60 / Q000235:genetics; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D018869:Heat-Shock Response / Q000187:drug effects*; D006358:Hot Temperature; D015227:Lipid Peroxidation / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects; D010100:Oxygen / Q000378:metabolism; D010788:Photosynthesis / Q000187:drug effects; D010798:Phycocyanin / Q000378:metabolism; D013312:Stress, Physiological / Q000187:drug effects
D000975:Antioxidants; D001426:Bacterial Proteins; D018835:Chaperonin 10; D018834:Chaperonin 60; D010798:Phycocyanin; D002734:Chlorophyll; D002338:Carotenoids; D002122:Calcium Chloride; D010100:Oxygen; D000077194:Chlorophyll A
Anabaena PCC7120; Antioxidative defense; Apoptosis; Heat shock; Photosynthetic O(2)-evolution; groEL/ES