Asparagine-based production of hydrogen peroxide triggers cell death in the diatom Phaeodactylum tricornutum

A glance at the French-speaking diatomist community (ADLaF 2019 meeting)

“…Crenier et al 2017), but also for microbial decomposers (bacteria and fungi) through complex interactions (Allen et al 2020). Future works should evaluate the effects of already acting abiotic stressors not only on the cell functioning (Laviale et al 2019b;Contreras and Gillard 2020) but also on these communities and subsequent consequences for the trophic networks. For this purpose, microbial fatty acids emerge as relevant proxies of ecosystem health (e.g.…”

Nitrogen utilization analysis reveals the synergetic effect of arginine and urea in promoting fucoxanthin biosynthesis in the mixotrophic marine diatom Phaeodactylum tricornutum

“…Thus, sufficient nitrogen is an essential nutrient for both cell growth and fucoxanthin biosynthesis in P. tricornutum. Phaeodactylum tricornutum can utilize not only inorganic nitrogen sources like nitrate, nitrite, and ammonium but also organic nitrogen sources like urea, tryptone, and amino acids (Smith et al, 2019;Contreras and Gillard, 2021;. Compared with nitrate and ammonium, P. tricornutum preferred to use urea, achieving a higher biomass concentration with no significant difference in fucoxanthin content (Zhang et al, 2016).…”

“…Compared with nitrate and ammonium, P. tricornutum preferred to use urea, achieving a higher biomass concentration with no significant difference in fucoxanthin content (Zhang et al, 2016). Furthermore, the fucoxanthin production was 3.45fold higher than that in the presence of urea when tryptone was used as a nitrogen source (Wang et al, 2021), and P. tricornutum could utilize most of the amino acids, in which the maximum uptake rate of nitrogen was reached by using arginine (Rees and Allison, 2006;Contreras and Gillard, 2021). Among 20 proteinogenic amino acids, arginine has four amino moieties, leading to the highest nitrogen to carbon ratio in the molecule.…”

“…Phaeodactylum tricornutum cells assimilate nitrogen through glutamine synthetase (GS) and glutamine 2-oxoglutarate aminotransferase (GOGAT) cycle working with transport systems (Smith et al, 2019). Nitrate, nitrite, ammonium, and several amino acids that are metabolized extracellularly are assimilated in the chloroplast via GSII-GOGAT Fd and shuttle nitrogen to the mitochondria through the aspartate system (Smith et al, 2019;Contreras and Gillard, 2021). In contrast, urea, arginine, and lysine are assimilated by mitochondrial GSIII-GOGAT a,b , and amino moieties are transported to the chloroplast through the alanine system (Flynn and Syrett, 1986;Smith et al, 2019).…”

Amino Acid Catabolism During Nitrogen Limitation in Phaeodactylum tricornutum

“…Diatoms are capable of assimilating dissolved nitrogen sources of different forms, including inorganic ones such as nitrate (NO 3 – ), nitrite (NO 2 – ), and ammonium (NH 4 + ) and organic ones such as urea and amino acids ( Jauffrais et al, 2016 ). Amino acids can be taken up by cells and intracellularly metabolized as diatom genomes containing plasma membrane amino acid transporters ( Armbrust et al, 2004 ; Sipler and Bronk, 2015 ), and they can also be oxidized by extracellular L -amino acid oxidase to produce α-keto acid, NH 4 + , and hydrogen peroxide ( Palenik and Morel, 1990 ; Rees and Allison, 2006 ; Contreras and Gillard, 2020 ). Under nitrogen stress, cellular protein content decreases and amino acid degradation occurs ( Guerra et al, 2013 ).…”