Metabolite shift in Medicago truncatula occurs in phosphorus deprivation

Symbiotic nitrogen fixation entails successful interaction between legume hosts and rhizobia that occur in specialized organs called nodules. N2-fixing legumes have higher demand of phosphorus (P) than legumes grown on mineral N. Medicago truncatula is an important model plant for characterization of effects of P deficiency at the molecular level. Hence, a study was carried out to address the alteration in metabolite levels of M. truncatula grown aeroponically and subjected to four weeks of P stress. First, GC-MS based untargeted metabolomics employed initially revealed changes in metabolic profile of nodules with increased levels of amino acids and sugars and decline in amounts of organic acids. Subsequently, LC-MS/MS was used to quantify these compounds including phosphorylated metabolites in overall plant. Our results showed drastic reduction in levels of organic acids and phosphorylated compounds in -P leaves with moderate reduction in -P roots and nodules. Additionally, sugars and amino acids were elevated in the whole plant under P deprivation. These findings provide evidence that N2-fixation in M. truncatula is mediated through N feedback mechanism that in parallel is related to C and P metabolism.

Transcriptome-Wide Identification and Expression Profiling of SPX Domain-Containing Members in Responses to Phosphorus Deprivation of Pinus massoniana

The SPX domain-encoding proteins are believed to play important roles in phosphorus (Pi) homeostasis and signal transduction in plants. However, the overall information and responses of SPXs to phosphorus deficiency in pines, remain undefined. In this study, we screened the transcriptome data of Pinus massoniana in response to phosphorus deprivation. Ten SPX domain-containing genes were identified. Based on the conserved domains, the P. massoniana SPX genes were divided into four different subfamilies: SPX, SPX-MFS, SPX-EXS, and SPX-RING. RNA-seq analysis revealed that PmSPX genes were differentially expressed in response to phosphorus deprivation. Furthermore, real-time quantitative PCR (RT-qPCR) showed that PmSPX1 and PmSPX4 showed different expression patterns in different tissues under phosphorus stress. The promoter sequence of 2284 bp upstream of PmSPX1 was obtained by the genome walking method. A cis-element analysis indicated that there were several phosphorus stress response-related elements (e.g., two P1BS elements, a PHO element, and a W-box) in the promoter of PmSPX1. In addition, the previously obtained PmSPX2 promoter sequence contained a W-box, and it was shown that PmWRKY75 could directly bind to the PmSPX2 promoter using yeast one-hybrid analysis in this study. These results presented here revealed the foundational functions of PmSPXs in maintaining plant phosphorus homeostasis.

Genome-Wide Analysis of Purple Acid Phosphatase Genes in Brassica rapa and Their Association with Pollen Development and Phosphorus Deprivation Stress

PAPs (purple acid phosphatases) belong to the metallo-phosphoesterase superfamily and play important roles in developmental processes, phosphorus foraging, and recycling. However, the specific functions of BrPAPs in Brassica rapa are poorly understood. In this study, 39 BrPAPs were identified and divided into three major clades and nine subgroups. In 8 of the 39 BrPAPs, some invariant amino acid residues were lost or shifted. Based on an expression profiling analysis, BrPAP11, 14, 20, 24, 29, and 34 were specifically expressed in fertile floral buds, indicating their critical roles during pollen development. A total of 21 BrPAPs responded to Pi deprivation in either shoots or roots. Of these, BrPAP4, 5, 19, and 21 were upregulated in roots under Pi depravation conditions, while BrPAP12 was upregulated in the roots in normal conditions. BrPAP28 was upregulated in shoots under Pi depravation conditions, indicating its function shifted compared with its Arabidopsis homolog, AtPAP26. The present work contributes to further investigation of BrPAPs as candidate genes for genetic improvement studies of low phosphorus tolerance as well as for creating male sterile lines based on gene editing methods in Brassica rapa.

The effect of phosphorus starvation on the fatty acid composition of Visheria strains

Fatty acids are widely used in various fields: in medicine, agriculture, in the production of dietary supplement and biofuels, for the maintenance of aquaculture. The main source of fatty acids is fish oil. The relevance of the search for an alternative to fish oil as a source of fatty acids remains relevant today. Many microalgae accumulate fatty acids in quantities sufficient for use in biotechnology. Many studies are currently being conducted on the biochemistry of eustigmatophyceae algae. Most representatives of this class accumulate such polyunsaturated fatty acids as eicosapentaenoic and docosahexaenoic, which are in demand in biotechnology, while maintaining the necessary growth rates of biomass. The strains of Vischeria vischeri described in this work were isolated from soil samples. The obtained fatty acid profiles show that the strains when growing on a BBM medium with a triple nitrogen concentration store a high percentage of saturated palmitic, monounsaturated palmitoleic and polyunsaturated eicosopentaenoic acids. In addition, one of the strains accumulates rare long-chain polyunsaturated fatty acids: stearidonic acid, eicosodienoic acid, and digomo-γ-linoleic acid. Also, an experiment on phosphorus deprivation was conducted with these strains: as a result of this study, it was found that the composition of the fatty acids of the strains practically did not change, however, the concentrations of saturated and monounsaturated acids became higher, and polyunsaturated ones decreased. This trend in changes in the concentrations of fatty acids remained for all the described strains. The strains have been shown to accumulate long-chain saturated fatty acids: behenic and cerotic.

A Study on the Effect of Macro- and Micro- Nutrients on Nannochloropsis oceanica Growth, Fatty Acid Composition and Magnetic Harvesting Efficiency

The effect of iron, manganese, phosphorus and nitrogen on growth and lipid synthesis of the microalgae Nannochloropsis oceanica CCMP1779, as well as their impact on the magnetic harvesting efficiency, are examined under their depriving cell culture conditions. Herein, it is demonstrated that nitrogen and manganese depletion primarily reduced cell growth while phosphorus and iron restriction led to higher dry biomass. Subsequently, the role of those nutrients on fatty acids profile was examined. Phosphorus and nitrogen restriction resulted in lower and higher lipid content, respectively. High amounts of polyunsaturated fatty acids like eicosapentaenoic acid are produced under iron and manganese depletion. Phosphorus deprivation favors monounsaturated fatty acids such as C18:1 and C16:1, while nitrogen restriction favors saturated fatty acid production like C14:0, C16:0 and C18:0. Since the presence/absence of macro- and micro-elements may affect the overall electrostatic charges on the outmost microalgae surface, it was also analyzed how these elements affect the magnetic harvesting efficiency. Results showed that phosphorus deprivation led to the best magnetic harvesting efficiency of N. oceanica cells (93%) as compared to other nutrient starvation as well as standard medium.