Chlamydomonas reinhardtii—A Reference Microorganism for Eukaryotic Molybdenum Metabolism

Abstract

Molybdenum (Mo) is vital for the activity of a small but essential group of enzymes called molybdoenzymes. So far, specifically five molybdoenzymes have been discovered in eukaryotes: nitrate reductase, sulfite oxidase, xanthine dehydrogenase, aldehyde oxidase, and mARC. In order to become biologically active, Mo must be chelated to a pterin, forming the so-called Mo cofactor (Moco). Deficiency or mutation in any of the genes involved in Moco biosynthesis results in the simultaneous loss of activity of all molybdoenzymes, fully or partially preventing the normal development of the affected organism. To prevent this, the different mechanisms involved in Mo homeostasis must be finely regulated. Chlamydomonas reinhardtii is a unicellular, photosynthetic, eukaryotic microalga that has produced fundamental advances in key steps of Mo homeostasis over the last 30 years, which have been extrapolated to higher organisms, both plants and animals. These advances include the identification of the first two molybdate transporters in eukaryotes (MOT1 and MOT2), the characterization of key genes in Moco biosynthesis, the identification of the first enzyme that protects and transfers Moco (MCP1), the first characterization of mARC in plants, and the discovery of the crucial role of the nitrate reductase–mARC complex in plant nitric oxide production. This review aims to provide a comprehensive summary of the progress achieved in using C. reinhardtii as a model organism in Mo homeostasis and to propose how this microalga can continue improving with the advancements in this field in the future.

Produced water treatment by semi-continuous sequential bioreactor and microalgae photobioreactor

“…Generally, copper serves as a growth factor for microalgae, while molybdenum and nickel play essential roles in nitrogen assimilation. Under certain conditions, molybdenum could be excreted from the microalgae cells to regulate the internal concentration of this element (Tejada-Jimenez et al 2023 ). Therefore, the increase of copper and molybdenum observed in the heavy metal determination was likely due to the BBM media utilized in this experiment.…”

Produced Water Treatment by Semi-Continuous Sequential Bioreactor and Microalgae Photobioreactor

“…Under certain conditions, molybdenum could be excreted from the microalgae cells in order to regulate the internal concentration of this element [59]. Hence, there is a belief that the presence of copper and molybdenum elements in the BBM media utilized in this experiment has contributed to its high concentration.…”

Tracing the Element: The Molecular Bases of Molybdenum Homeostasis in Legumes

“…Of particular interest is that the expression of the MOT2 gene is activated by molybdate deficiency and is unresponsive to nitrate availability. The latter represents an opposite regulation to that of MOT1 [83]. In Arabidopsis, AtMOT2 participates in Mo accumulation during leaf senescence and in the export of Mo from vacuoles [84].…”

“…In plants, SO is involved in plant protection from sulfite toxicity under a SO 2 -rich atmosphere [137]. SO mARC catalyzes the reduction of hydroxylated compounds, mostly N-hydroxylated nucleobases and nucleosides: N-hydroxycytosine (NHC), the base analogue of 6-hydroxylaminopurine (HAP; in plants [138]), N-hydroxycytidine, and N-hydroxyadenosine [83,139]. NOFNiR activity can catalyze nitric oxide (NO) formation from nitrite and is strictly dependent on NR diaphorase activity but is independent of the NR Moco domain [140][141][142].…”

“…Plants require a sufficient supply of molybdenum to ensure the activity of molybdoenzymes that are found in other eukaryotes, including nitrate reductase, xanthine dehydrogenase, sulfite oxidase, aldehyde oxidase, and mARC [83]. Plant NR catalyzes the principal step of the reduction of nitrate to nitrite in inorganic nitrogen assimilation and the reduction of nitrite to nitric oxide (NO) [83].…”