Effect of exogenous phosphatase and phytase activities on organic phosphate mobilization in soils with different phosphate adsorption capacities

Abstract

This study evaluated the effects of exogenous LASAP2 for acid phosphatase (APase) and LASAP3 for phytase of white lupin (Lupinus albus L.) on phosphorus (P) accumulation from organic P in soils. The potential for LASAP2-overexpressing tobacco (Nicotiana tabacum L.) to increase organic P in soil was examined in our previous study. However, LASAP2 has low specificity for phytate, the predominant form of unavailable P in the brown lowland soil. For the present study, we isolated the full length of LASAP3 cDNA and introduced it into tobacco plants using Agrobacterium-mediated transformation. Transgenic tobacco plants were grown in two different soils (Andosols and Regosols; high and low P-adsorption capacity, respectively) supplemented with either inorganic phosphate (þPi) or phytate (Po) as the sole P source, or control conditions that lacked phosphorus (No P). Dry matter production and P content of the transgenic line was higher than that of wild type in all treatments. The ratio of P accumulation increase by exogenous enzymes was found to be dependent on the P treatment and soil type. In all lines, the increase in þPo was less than that in þPi, but higher than in No P. The P uptake ability of plants in Regosols was higher than in Andosols for all treatments, suggesting that the P utilization efficiency of both Pi and Po is dependent on the solubility. In no soil type or P treatment was a significant difference found between LASAP2-and LASAP3-overexpressing lines. These results demonstrate that introducing an APase and phytase gene such as LASAP2 and LASAP3 into tobacco by genetic transformation is a promising strategy for improving P mobilization in soil, although the bottleneck for mobilization of phytate-P is not the specificity of the enzyme but its solubility in soils.

Organic acid excretion from roots: a plant mechanism for enhancing phosphorus acquisition, enhancing aluminum tolerance, and recruiting beneficial rhizobacteria

“…This secretion has synergetic effects in P-acquisition by white lupin, which is supported by a recent transgenic study that found a combined beneficial effect of citrate excretion and phytase secretion for improved P-acquisition (Giles et al 2017). On the other hand, overexpression of LASAP2 (a gene that causes root secretion of acid phosphatase in white lupin) in tobacco was found to enhance P accumulation from Regosol, harboring low-P-adsorption capacity (Maruyama et al 2012). Some OA transporters are additionally induced by -P, which contributes additively to enhance P-acquisition.…”

Organic anions facilitate the mobilization of soil organic phosphorus and its subsequent lability to phosphatases

“…Indeed 'the success' of white lupin to acquire P appears to rely on both the formation of cluster roots and 'their cocktail' of exudates, comprised of organic anions, protons, phosphatases and secondary metabolites to inhibit microbial activity (Neumann et al 1999;Weisskopf et al 2006). The phosphatases released by white lupin include isoforms with a broad speci city including those with phytase activity (Tadano et al 1993;Maruyama et al 2012). Moreover, when tobacco plants were genetically modi ed to enhance citrate and phytase exudation together, they showed a greater ability to utilize organic P from soils than lines modi ed to release citrate or phytase alone (Giles et al 2017).…”

Release of acid phosphatase from extraradical hyphae of arbuscular mycorrhizal fungusRhizophagus clarus

“…Secretion of ACP into the rhizosphere/hyphosphere, however, has been demonstrated only in limited ranges of plants (e.g., Tarafdar and Claassen 1988;Tadano and Sakai 1991) and fungi (e.g., Van Aarle and Plassard 2010; Crowther et al 2011). In plants, secreted ACP hydrolyzes organic phosphate, increases the P i pool in the rhizosphere and thus enhances P i uptake (Wasaki et al 2009;Maruyama et al 2012;Robinson et al 2012).…”