Systems‐level analysis of the metabolic responses of the diatom Phaeodactylum tricornutum to phosphorus stress

Abstract

SummaryPhosphorus is an important macronutrient. To understand the molecular and cellular responses to phosphorus stress better, transcriptome profiling in combination with biochemical investigations was conducted in the model diatom Phaeodactylum tricornutum. Out of 10 402 predicted genes, 2491 and 405 genes were significantly upregulated or downregulated respectively. Unsurprisingly, genes associated with phosphate uptake were upregulated, such as the phosphate transporters and alkaline phosphatases. Genes encoding stress-shock proteins were accordingly upregulated, including genes associated with stress-responsive proteins, signal transduction and secondary metabolism. Additionally, genes related to protein translation, carbon fixation, glycolysis and the citric acid cycle were also upregulated. Genes associated with gene transcription were downregulated, thereby resulting in the upregulation of translation to compensate for the limited supply of messenger RNA. The downregulation of genes related to β-oxidation could contribute to the accumulation of fatty acids. Accordingly, triacylglycerols, which are important for energy storage, were determined to increase by 1.65-fold. Intracellular membranes, other than chloroplast membranes, tended to be dispersed; this finding was in accordance with the increased transcription of a total of 11 genes encoding putative phospholipases. Taken together, this work revealed the coordination of multiple metabolic pathways and certain key genes in the adaptation of P. tricornutum to phosphorus stress.

Intraspecific variation in alkaline phosphatase activity in Phaeodactylum tricornutum (Bacillariophyceae, Bohlin)

“…3), indicating that AP activity is higher in cells under conditions of low phosphate concentrations. Th ese results agree with previous studies (González-Gil et al 1998;Beardall et al 2001;Dyhrman & Palenik 2001;Moser et al 2010;Yang et al 2014), since this microalgae is able to use a strategy of organic phosphorus incorporation when the inorganic form of this nutrient is limited (Rengefors et al 2001;Nedoma et al 2003). On the other hand, the control and F treatment and Ub7 (B) in Control (C), F and F/8 treatments.…”

“…4), which suggests increased uptake of phosphate by this algae. Intraspecifi c variation in AP activity in P. tricornutum has been previously reported, hence this microalgae is used worldwide in bioassays of algal growth potential (Yang et al 2014 and references therein). Lin et al (2013) observed that P. tricornutum growing in a starved medium had intense AP activity from the fourth to the seventh day of incubation, and that AP mRNA expression was abundant.…”

“…Lin et al (2013) observed that P. tricornutum growing in a starved medium had intense AP activity from the fourth to the seventh day of incubation, and that AP mRNA expression was abundant. Additionally, Yang et al (2014) found two genes responsible for encoding alkaline phosphatases in P. tricornutum, which exhibit sharp rises in their transcription when limited by phosphorus. In such conditions, the increase in AP activity may be related to the incorporation of organic phosphorus.…”

“…In those defi ciency circumstances, P. tricornutum are able to absorb from 8 to 16 times as much as the minimum cell quota, by converting phosphate into intracellular polyphosphate reserves to support three to four generations in conditions of phosphate depletion (Yao et al 2011). Th e isolated strains of the same species may refl ect signifi cant genetic variability that is refl ected in variability of characters of cellular physiology (Gallagher 1980;1982;Huang et al 2011;Yang et al 2014). Th is agrees with our results, since Ub3 and Ub7 both showed diff erent responses in relation to absorption and phosphate assimilation, as shown by their absorption rates (Tab.…”

“…and Isochrysis galbana (González-Gil et al 1998);and Phaeodactylum tricornutum (i.e. Lin et al 2013;Yang et al 2014). On the other hand, Marco & Orus (1988) observed that the cyanobacteria Trichodesmium sp.…”