Using a trait-based approach to optimize mixotrophic growth of the red microalga Porphyridium purpureum towards fatty acid production.

BACKGROUND: Organic carbon sources have been reported to simultaneously increase the growth and lipid accumulation in microalgae. However, there have been no studies of the mixotrophic growth of Porphyridium purpureum in organic carbon media. In this study, three organic carbon sources, glucose, sodium acetate, and glycerol were used as substrates for the mixotrophic growth of P. purpureum. Moreover, a novel trait-based approach combined with Generalized Additive Modeling was conducted to determine the dosage of each organic carbon source that optimized the concentration of cell biomass or fatty acid. RESULTS: A 0.50% (w/v) dosage of glucose was optimum for the enhancement of the cell growth of P. purpureum, whereas sodium acetate performed well in enhancing cell growth, arachidonic acid (ARA) and eicosapentaenoic acid (EPA) content, and glycerol was characterized by its best performance in promoting both cell growth and ARA/EPA ratio. The optimum dosages of sodium acetate and glycerol for the ARA concentration were 0.25% (w/v) and 0.38% (v/v), respectively. An ARA concentration of 211.47 mg L-1 was obtained at the optimum dosage of glycerol, which is the highest ever reported. CONCLUSIONS: The results suggested that a comprehensive consider of several traits offers an effective strategy to select an optimum dosage for economic and safe microalgae cultivation. This study represents the first attempt of mixotrophic growth of P. purpureum and proved that both biomass and ARA accumulation could be enhanced under supplements of organic carbon sources, which brightens the commercial cultivation of microalgae for ARA production.

Comparative transcript profiling of maize inbreds in response to long-term phosphorus deficiency stress.

Maize (Zea mays L.) is an important food and energy crop, and low phosphate (Pi) availability is one of the major constraints in maize production worldwide. Plants adapt suitably to acclimate to low Pi stress. However, the underlying molecular mechanism of Pi deficiency response is still unclear. In this study, comparative transcriptomic analyses were conducted to investigate the differences of transcriptional responses in two maize genotypes with different tolerances to low phosphorus (LP) stress. LP-tolerant genotype QXN233 maintained higher P and Pi levels in shoots than LP-sensitive genotype QXH0121 suffering from Pi deficiency at seedling stage. Moreover, the transcriptomic analysis identified a total of 1391 Pi-responsive genes differentially expressed between QXN233 and QXH0121 under LP stress. Among these genes, 468 (321 up- and 147 down-regulated) were identified in leaves, and 923 (626 up- and 297 down-regulated) were identified in roots. These Pi-responsive genes were involved in various metabolic pathways, the biosynthesis of secondary metabolites, ion transport, phytohormone regulation, and other adverse stress responses. Consistent with the differential tolerance to LP stress, five maize inorganic Pi transporter genes were more highly up-regulated in QXN233 than in QXH0121. Results provide important information to further study the changes in global gene expression between LP-tolerant and LP-sensitive maize genotypes and to understand the molecular mechanisms underlying maize's long-term response to Pi deficiency.

[Dosage-toxicity-efficacy relationship of Kansui Radix in malignant pleural effusion models based on Walker 256 analysis].

To investigate the dosage-toxicity-efficacy relationship of Kansui Radix, explore its regularity of the toxicity and efficacy change, and provide scientific basis for its clinical rational application, the malignant pleural effusion models were used to observe the effect of Kansui Radix with larger dose range (0.045-1.620 g•kg•d⁻¹ for Kansui Radix) on biochemical indexes and hydrothorax volume in experimental animals. Factor analysis method was also used to comprehensively assess the dosage-toxicity-efficacy relationship of Kansui Radix. The results showed that the rats in model group had larger hydrothorax volume, and ALT, AST, LDH, HBDH, IFN-γ, IL-2 and TNF-α levels were significantly increased (P<0.05), while TP and ALB levels were decreased (P<0.05) as compared with the blank group. After drug administration, various treatment groups decreased hydrothorax volume, IFN-γ, IL-2, TNF-α and increased TP and ALB levels as compared with model group, indicating certain therapeutic effect; and increased ALT, AST, LDH and HBDH levels, indicating certain liver and cardiac toxicity. In the factor analysis, two common factors were extracted from nine indexes, explaining 89.1% of the information. The analysis results suggested that there was no obvious toxicity in case of independent use of Kansui Radix within the dosage range set in pharmacopeia, while it would produce liver toxicity and cardiac toxicity upon 3 times of the dosage set in pharmacopeia, and the toxicity was increased with the increase of dose. At the same time, Kansui Radix can decrease the hydrothorax volume in malignant pleural effusion models and improve relevant physical indexes in a dose-dependent manner. Comprehensive analysis results of its toxic effect characteristics indicated that the upper-limit dose of Kansui Radix in pharmacopeia shall be regarded as the relatively optimal therapeutic dose.