Overexpression of phyA and appA Genes Improves Soil Organic Phosphorus Utilisation and Seed Phytase Activity in Brassica napus

Abstract

Phytate is the major storage form of organic phosphorus in soils and plant seeds, and phosphorus (P) in this form is unavailable to plants or monogastric animals. In the present study, the phytase genes phyA and appA were introduced into Brassica napus cv Westar with a signal peptide sequence and CaMV 35S promoter, respectively. Three independent transgenic lines, P3 and P11 from phyA and a18 from appA, were selected. The three transgenic lines exhibited significantly higher exuded phytase activity when compared to wild-type (WT) controls. A quartz sand culture experiment demonstrated that transgenic Brassica napus had significantly improved P uptake and plant biomass. A soil culture experiment revealed that seed yields of transgenic lines P11 and a18 increased by 20.9% and 59.9%, respectively, when compared to WT. When phytate was used as the sole P source, P accumulation in seeds increased by 20.6% and 46.9% with respect to WT in P11 and a18, respectively. The P3 line accumulated markedly more P in seeds than WT, while no significant difference was observed in seed yields when phytate was used as the sole P source. Phytase activities in transgenic canola seeds ranged from 1,138 to 1,605 U kg–1 seeds, while no phytase activity was detected in WT seeds. Moreover, phytic acid content in P11 and a18 seeds was significantly lower than in WT. These results introduce an opportunity for improvement of soil and seed phytate-P bioavailability through genetic manipulation of oilseed rape, thereby increasing plant production and P nutrition for monogastric animals.

Molecular mechanisms underlying phosphate sensing, signaling, and adaptation in plants

“…Among them, overexpression of phytase and phosphatase genes has generally resulted in an increase in P efficiency of host plants, regardless of the origin of the genes. Notable examples include AtPAP15 in soybean (Wang et al ), MtPHY1 in clover (Ma et al ), OsPAP10a in rice (Tian et al ), PhyA from Aspergillus niger in clover, cotton, and rapeseed (George et al ; Liu et al ; Wang et al ), and appA from Escherichia coli in potato and rapeseed (Hong et al ; Wang et al ).…”

Biotechnology of nutrient uptake and assimilation in plants

“…More recently, the expression of two different phytase genes (phyA and appA, from Aspergillus niger and E. coli, respectively) in canola produced transgenic seeds with lower amounts of phytic acid than the wild-type. Although the authors did not perform Fe analysis, it could be expected that Fe bioavailability could have also been improved (Wang et al, 2013b), representing a better solution for the nutrient availability of P and Fe, at least for monogastric animals.…”

A novel extracellular low‐temperature active phytase from Bacillus aryabhattai RS1 with potential application in plant growth

“…Phosphorus is an essential nutrient for plants and animals. Phytic acid ( myo ‐inositol 1,2,3,4,5,6‐hexakis phosphate, IP6) and its mixed cation salt, phytate, are the major storage forms of phosphorus (60–80%) in cereals and legumes, that are unavailable to monogastric animals . Phytate is also strongly complexed in soil, representing an important class of organic phosphate poorly available to plants .…”

“…The enzyme is widespread in nature, occurring in plants, animals and microorganisms. Phytases from these sources exhibit variations in structure and catalytic mechanism and consequently, have been categorized into cysteine phytase, histidine acid phosphatase, β‐propeller phytase (BPP), and purple acid phosphatase families . Several Gram‐positive and Gram‐negative soil bacteria such as, Citrobacter braakii, Obesumbacterium proteus , Bacillus subtilis , Escherichia coli , Erwinia carotovora, and Yersinia intermedia, are known to produce phytase .…”