Protistology 12 (2), 97–108 (2018) |
Sulfur deprivation-induced expression of THB1, a Chlamydomonas reinhardtii truncated hemoglobin, is mediated by nitrate reductase-dependent NO production |
Biological Faculty, Saint-Petersburg State University, St. Petersburg, 199034, Russia | Submitted June 21, 2018 | Accepted July 12, 2018 | Summary During sulfur (S) deprivation, Chlamydomonas reinhardtii mediates a suite of specific responses to efficiently acquire S from various sources and remodel primary metabolism. Although the truncated hemoglobin 1 (THB1)-dependent regulation of a subset of S limitation-responsive genes has been elucidated, the mechanism through which THB1 transcription is triggered in S-deprived cells is not known. Here, we show that signaling proteins and regulators associated with S deprivation specific responses did not control THB1 expression. Following S depletion, rapid increase in nitrite concentrations is essential for THB1 upregulation. These changes are consistent with NO accumulation. Increased nitrite, NO and THB1 mRNA levels were not observed in mutant cells without diaphorase-NR activity. Our findings suggest that nitrate reductase - nitric oxide-forming nitrite reductase system plays a positive role in THB1 transcription via generation of NO from nitrite in S-starved cells. NR-dependent NO production may be regarded as an early trigger, which contributes to Chlamydomonas adaptability to nutrient stresses.
Key words: nitrate reductase, nitric oxide, sulfur limitation responses, truncated hemoglobin 1
Address for correspondence: Elena Ermilova. Biological Faculty, Saint-Petersburg State University, Universitetskaya nab. 7/9, Saint-Petersburg, 199034, Russia; e-mail: e.ermilova@spbu.ru |
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