Fig. 5
Evolution of CYN genes and tolerance to cyanate. A The histogram shows the biomass yield of three microalgae (N. oculata, V. stellata, and V. cf. polyphem) under four different initial NaNO3 concentrations. These data were adopted from Wang et al. [17]. B Overview of nitrogen metabolism pathways during amino acid synthesis and degradation. C The numbers of urea cycle genes in the two sequenced microalgae and nine other heterokontophytes. Abbreviations: VH4302, V. sp. H4302; VC74, V. sp. C74; Vs, V. stellata; MC73, Mo. sp. C73; MC141, Mo. sp. C141, Mg, Mi. gaditana; No, N. oceanica; Es, E. siliculosus; Sj, S. japonica; Pt, P. tricornutum; Tp, T. pseudonana. Genes: OTC, ornithine transcarbamylase; ASS: argininosuccinate synthase; ASL, argininosuccinate lyase; ARG, arginase. D Phylogenetic tree of CYN genes from thirteen heterokontophytes (left panel) and the RNA expression of five CYN genes of V. cf. polyphem’s (left panel). “*” means this gene is missing in released geneset and is predicted through a homology-based prediction in this study and the target gene ID is shown as above. E The biomass accumulation curves of N. oculata, V. stellata, and V. cf. polyphem with two kinds of nitrogen source (NaCNO and NaNO3) under two initial nitrogen concentrations (1 and 2 mM). Each data point represents the mean ± SD of three biological and technical triplicates. *, P-value < 0.05, **, P-value < 0.01