Amino Acid Catabolism During Nitrogen Limitation in Phaeodactylum tricornutum

Abstract

Diatoms can accumulate high levels of triacylglycerols (TAGs) under nitrogen depletion and have attracted increasing attention as a potential system for biofuel production. In Phaeodactylum tricornutum, a model diatom, about 40% of lipid is synthesized from the breakdown of cellular components under nitrogen starvation. Our previous studies indicated that carbon skeletons from enhanced branched-chain amino acid (BCAA) degradation under nitrogen deficiency contribute to TAG biosynthesis in P. tricornutum. In this review, we outlined the catabolic pathways of all 20 amino acids based on the genome, transcriptome, proteome, and metabolome data. The contribution of these amino acid catabolic pathways to TAG accumulation was also analyzed.

The Transition Toward Nitrogen Deprivation in Diatoms Requires Chloroplast Stand-By and Deep Metabolic Reshuffling

“…Branched-Chain amino acids (BCAA) have been reported to be involved in the accumulation of triacylglycerols (TAG) (Ge et al, 2014 ; Liang et al, 2019 ; Pan et al, 2020 ). Most of the genes involved in the BCAA degradation were upregulated ( Supplementary Figure 10 ).…”

Predator cues target signaling pathways in toxic algal metabolome

“…Metabolism of the amino acids valine and arginine were both impacted (Table 1), consistent with disruptions to amino acid metabolism observed, via transcriptomics, in Pseudo‐nitzschia seriata , Phaeodactylum tricornutum , and Alexandrium tamarense in the presence of copepods (Wohlrab et al 2010; Li and Ismar 2018; Harðardóttir et al 2019). Altered regulation in branched‐chain amino acid biosynthesis has been linked to both triacylglycerol accumulation (Ge et al 2014; Pan et al 2020) and interactions with bacterial communities in diatoms (Ferrer‐González et al 2021). However, what role branched‐chain amino acids serve in toxin production is unclear.…”

Multiomics approaches and genetic engineering of metabolism for improved biorefinery and wastewater treatment in microalgae

“…[ 142,143 ] Using a mutant (bkdE1α) that is deficient in the E1α subunit of the branched‐chain keto acid dehydrogenase (BCKDH) complex, the enzyme of the BCAA catabolic pathway, the catabolism of BCAA by BCKDH provides C for fatty acid biosynthesis in C. reinhardtii . [ 144 ]…”

“…[142,143] Using a mutant (bkdE1α) that is deficient in the E1α subunit of the branched-chain keto acid dehydrogenase (BCKDH) complex, the enzyme of the BCAA catabolic pathway, the catabolism of BCAA by BCKDH provides C for fatty acid biosynthesis in C. reinhardtii. [144] TFs are also involved in the regulation of C flux toward lipid biosynthesis (Figure 2). In a marine microalga N. oceanica, the overexpression of a transcriptional factor, basic-region/leucine zipper (bZIP), causes an increase in lipid contents.…”

“…In the future, the mechanisms underlying the tolerance of commercially available microalgae to harsh environments such as overdose or low nutrient level, low-intensity and overdose illumination, low and high temperature, salinity fluctuations (evaporation or rain), low dissolved oxygen level, toxins, and biotic contaminations [144,193] need more studies in cooperation with multiomics analysis for the comprehensive understanding of stress responses. The genetic engineering entire or different pathways to adapt complicated wastewater conditions and for industrial application in biorefinery offer an avenue to resolve this challenging.…”