Nitric oxide generation upon growth of Antarctic Chlorella sp. cells

Abstract

The aim of this work was to characterize nitric oxide (NO) generation during the growth of Chlorella sp. cells. The profile of NO production was compared with that observed in Chlorella from temperate climate and Antarctic Chlamydomonas sp. A distinctive electron paramagnetic resonance (EPR) signal for the adduct MGD-Fe-NO was detected in the Antarctic Chlorella sp. cells on days 6 and 7 of growth. An assay based upon the time-dependent detection of NO by EPR was developed to assess both nitrate reductase (NR) and NO synthase (NOS)-like activities. A significant increase in both enzymatic activities was observed on day 6 of growth of Antarctic Chlorella sp. cells. However, NOS-like activity proved undetectable on day 10 of growth, while NR activity was observed until day 22 of growth. When the cultures were supplemented with No-nitro-L-arginine methyl ester (L-NAME) from day 0 to day 13, no growth was observed. After administration of L-NAME from day 5 to day 12, growth rate at log phase was inhibited from 0.18 AE 0.02 (control) to 0.11 AE 0.01 per day. Removal of L-NAME on day 12 increased the growth rate to 0.15 AE 0.02 per day. Supplementation with S-nitroso-N-acetylpenicillamine on day 5, in the presence of L-NAME from day 0, restored the growth rate to control values. The same profile of NO generation was observed during the growth of Antarctic Chlamydomonas sp.; however, Chlorella cells from temperate climate did not show any difference in NO generation over the growth period. The data reported here are the first observations, by employing EPR, of NO and the activity of the enzymes responsible for its generation during the growth of Antarctic photosynthetic alga.Abbreviations -EPR, electron paramagnetic resonance; L-NAME, No-nitro-L-arginine methyl ester; MGD, sodium-N-methyl-D-glucamine dithiocarbamate; NOS, nitric oxide synthase; NR, nitrate reductase; SNAP, S-nitroso-N-acetyl-penicillamine; TEMPO, 2,2,5,5-tetramethyl piperidine 1-oxyl.

THE ROLE OF NITRIC OXIDE IN DIATOM ADHESION IN RELATION TO SUBSTRATUM PROPERTIES1

“…In fact, when production of NO was inhibited by the NOS inhibitor NMMA, growth was inhibited, implying that NO may play a protective role in Seminavis. Inhibition of growth by addition of NOS inhibitors was also seen in sea urchin embryos and in Antarctic Chlorella and Chlamydomonas (Estevez and Puntarulo 2005). Although addition of the inactive optical isomer of the NOS inhibitor to sea urchin embryos resulted in some inhibition of growth, it was not to the extent seen with the active isomer, and hence the inhibitory effect on morphogenesis was attributed to a suppression of NO production (Semenova and Ozernyuk 2004).…”

“…In algae, research into NO signaling is in its infancy. General production of NO in algae, such as Chlamydomonas (Sakihama et al 2002), Antarctic Chlorella (Estevez and Puntarulo 2005), Dasycladus (Ross et al 2006), Scenedesmus (Mallick et al 2002), dinoflagellates (Zhang et al 2006), and in the diatom Skeletonema (Zhang et al 2006) has been shown. In the chlorophyte alga Dascycladus vermicularis , NO is produced as a result of wounding, leading to a healing response (Ross et al 2006).…”

Nitric oxide in marine photosynthetic organisms

“…[27]. Few other studies reported the presence of little amounts of NO, in the order of 10 -8 -10 -9 mol/l, in the culture medium of several marine microalgae, such as H. akashiwo, Chaetoceros curvisetus, Tetraselmis subcordiformis, S. costatum and Gymnodinium sp..…”

Involvement of ethylene and nitric oxide in cell death in mastoparan‐treated unicellular alga Chlamydomonas reinhardtii

“…Representing both single cells and an entire organism, the unicellular alga Chlamydomonas is a suitable model system to study cell death. It is an established model for elucidation of heavy metal tolerance, stress validation and physiological processes such as respiration, photosynthesis, cell propagation and nutrient uptake (Harris, 2001; Hanikenne, 2003; Hema et al, 2007; Deponte, 2008). Exposure of Chlamydomonas reinhardtii to UV has been shown to induce hallmarks of apoptotic‐like PCD such as the breakdown of DNA into oligonucleosomal fragments (DNA laddering) and occurrence of TUNEL (terminal deoxynucleotidyl transferase‐mediated dUTP nick end labelling)‐positive nuclei (Moharikar and D'Souza, 2006).…”