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Elena Ermilova

Elena Ermilova

Saint-Petersburg State University, Russia

Title: Nitric oxide and truncated hemoglobin 1 in regulation of sulfur deprivation responses in Chlamydomonas


Biography: Elena Ermilova


Statement of the Problem: Sulfur (S) is an essential element among catalysts and intermediates of primary metabolism. S can be limiting in the environment and strongly influence ecosystem composition. During S deprivation, metabolism of Chlamydomonas cells is refocused on both scavenging the nutrient and remodeling primary metabolism. Although some signaling proteins and regulators of S-specific responses have been identified, the mechanisms triggering the coordinated responses in different cellular compartments are not absolutely clear. Previously, we have reported that nitric oxide is generated upon S deprivation.

Purpose: The purpose of this study is to elucidate the role of nitric oxide (NO) and truncated hemoglobin 1 (THB1) in modulating early responses to S deficiency in different compartment of Chlamydomonas cells.

Methodology & Theoretical Orientation: To examine transcriptional regulation of a subset of S limitation-responsive genes and role of NO and THB1 in signaling pathway associated with S deprivation, real-time PCR analysis and artificial microRNA method were employed. A comparative analysis of gene expression and NO generation in wild type, nitrate reductase mutants and THB1 knock-down transformant was utilized to understand the functional consequences of NO production.

Findings: In S-free medium, Chlamydomonas cells produced NO apparently via nitrate reductase. We found that in S-limited cells NO is important to upregulate some S deficiency-inducible genes (THB1) and repress the others (FDX5, ARS1, ARS2, SULTR2, SLT1 and SLT2). THB1 is involved in this NO-dependent process.

Conclusion & Significance: Together, the results demonstrated that THB1 has implicated to function as NO regulator (via conversion of NO into nitrate) and thereby initiate NO-based signaling cascades in S-depleted cells. Moreover, NO generation may be regarded as an early trigger, which contributes to Chlamydomonas adaptability to S starvation.