Identification of individual components of a commercial wheat germ acid phosphatase preparation

Wheat germ acid phosphatase (WGAP) is a commercial preparation of partially purified protein commonly used in laboratory settings for non-specific enzymatic dephosphorylation. It is known that these preparations contain multiple phosphatase isozymes and are still relatively crude. This study therefore aimed to identify the protein components of a commercial preparation of wheat germ acid phosphatase using mass spectroscopy and comparative genomics. After one post-purchase purification step, the most prevalent fifteen proteins in the mixture included heat shock proteins, beta-amylases, glucoseribitol dehydrogenases, enolases, and an aminopeptidase. While not among the most abundant components, eight unique dephosphorylation enzymes were also present including three purple acid phosphatases. Furthermore, it is shown that some of these correspond to previously isolated isozymes; one of which has been also previously shown by transcriptome data to be overexpressed in wheat seeds. In summary, this study identified the major components of WGAP including phosphatases and hypothesizes the most active components towards a better understanding of this commonly used laboratory tool.

Identification and Functional Analysis of Two Purple Acid Phosphatases AtPAP17 and AtPAP26 Involved in Salt Tolerance in Arabidopsis thaliana Plant

Tolerance to salinity is a complex genetic trait including numerous physiological processes, such as metabolic pathways and gene networks; thereby, identification of genes indirectly affecting, as well as those directly influencing, is of utmost importance. In this study, we identified and elucidated the functional characterization of AtPAP17 and AtPAP26 genes, as two novel purple acid phosphatases associated with high-salt tolerance in NaCl-stressed conditions. Here, the overexpression of both genes enhanced the expression level of AtSOS1, AtSOS2, AtSOS3, AtHKT1, AtVPV1, and AtNHX1 genes, involving in the K+/Na+ homeostasis pathway. The improved expression of the genes led to facilitating intracellular Na+ homeostasis and decreasing the ion-specific damages occurred in overexpressed genotypes (OEs). An increase in potassium content and K+/Na+ ratio was observed in OE17 and OE26 genotypes as well; however, lower content of sodium accumulated in these plants at 150 mM NaCl. The overexpression of these two genes resulted in the upregulation of the activity of the catalase, guaiacol peroxidase, and ascorbate peroxidase. Consequently, the overexpressed plants showed the lower levels of hydrogen peroxide where the lowest amount of lipid peroxidation occurred in these lines. Besides the oxidation resistance, the boost of the osmotic regulation through the increased proline and glycine-betaine coupled with a higher content of pigments and carbohydrates resulted in significantly enhancing biomass production and yield in the OEs under 150 mM NaCl. High-salt stress was also responsible for a sharp induction on the expression of both PAP17 and PAP26 genes. Our results support the hypothesis that these two phosphatases are involved in plant responses to salt stress by APase activity and/or non-APase activity thereof. The overexpression of PAP17 and PAP26 could result in increasing the intracellular APase activity in both OEs, which exhibited significant increases in the total phosphate and free Pi content compared to the wild-type plants. Opposite results witnessed in mutant genotypes (Mu17, Mu26, and DM), associating with the loss of AtPAP17 and AtPAP26 functions, clearly confirmed the role of these two genes in salt tolerance. Hence, these genes can be used as candidate genes in molecular breeding approaches to improve the salinity tolerance of crop plants.

Organophosphorus hydrolysis by diatom purple acid phosphatase and sequential regulation of cell metabolism

Phosphorus (P) limitation affects the phytoplankton growth and population in aquatic systems, consequently limits aquatic primary productivity. To cope with P limitation, plants have evolved a range of metabolic responses such as accumulation of purple acid phosphatases (PAP) to enhance phosphates acquisition. However, it remains unknown whether algae adopt a similar mechanism. Here we exemplified the role of PAPs in the model microalga Phaeodactylum tricornutum. PAP1 expression was enhanced in P. tricornutum cells grown on organophosphorus compared to inorganic phosphate. PAP1 overexpression ameliorated cellular growth and biochemical composition in a growth-phase dependent manner. PAP1 promoted growth and photosynthesis during growth phases and reallocated carbon flux towards lipogenesis in the stationary phase. PAP1 was ER localized and orchestrated the expression of genes involved in key metabolic pathways and Pi translocation, thereby ameliorated energy, reducing equivalents and antioxidant potential. PAP1 silencing induced its homolog PAP2 expression, thereby replenished Pi scavenging activity of PAP1. Our investigation unravels the PAP1 associated metabolic regulations in a sequential manner, providing a novel insight in algal phosphorus metabolism and aquatic primary productivity.