A New Hypothesis on the Strategy for Acquisition of Phosphorus in Arbuscular Mycorrhiza: Up-Regulation of Secreted Acid Phosphatase Gene in the Host Plant

Abstract

The mycorrhiza-responsive phosphatase of Tagetes patula in symbiosis with Glomus etunicatum was detected by electrophoresis, was purified by column chromatography, and was characterized as acid phosphatase that was secreted into rhizosphere. The N-terminal amino acid sequence was determined by a gas-phase sequencer, and a cDNA fragment of the phosphatase gene (TpPAP1) was amplified by degenerate primers designed based on the N-terminal amino acid sequence. The full-length cDNA was obtained by the rapid amplification of cDNA ends technique. The TpPAP1 was of host origin, and the cDNA was 1,843 bp long with a predicted open reading frame of polypeptide of 466 amino acids. Phylogenetic analysis revealed that the gene fell into the cluster of plant high-molecular-weight purple acid phosphatase. Expression analysis of the TpPAP1 in T. patula in symbiosis with Archaeospora leptoticha showed that the levels of transcripts increased eightfold by mycorrhizal colonization. Western blot analysis revealed that the 57-kDa protein corresponding to the mycorrhiza-responsive phosphatase increased by mycorrhizal colonization. The present study proposes a new strategy for acquisition of P in arbuscular mycorrhizal associations in which the fungal partner activates a part of the low-P adaptation system of the plant partner, phosphatase secretion, and improves the overall efficiency of P uptake.

Arbuscular mycorrhizal fungi and organic fertilizer influence photosynthesis, root phosphatase activity, nutrition, and growth of Ipomoea carnea ssp. fistulosa

“…Our understanding of the biochemical and biophysical process involved in P metabolism and phosphatase synthesis and activity continues to evolve (Tarafdar et al 2001, van Aarle et al 2002, Ezawa et al 2005, Javot et al 2007. While AMF mycelia can mineralize organic P (Feng et al 2003), AMF can also enhance P acquisition via up-regulation of acid phosphatase gene expression and secretion in host plant roots (Ezawa et al 2005).…”

“…While AMF mycelia can mineralize organic P (Feng et al 2003), AMF can also enhance P acquisition via up-regulation of acid phosphatase gene expression and secretion in host plant roots (Ezawa et al 2005). Due to the important role of root phosphatase enzymatic activity on the bioavailability of organic phosphorus (P o ) sources, we followed the changes of ACP and ALP during the growth of AMF and NonAMF I. carnea at different OSRF rates.…”

Sanctions, Cooperation, and the Stability of Plant-Rhizosphere Mutualisms

“…Colonization of Tagetespatula by Glomus etunicatum induced expression and secretion of a plant-derived acid phosphatase, which acted to further liberate P in the rhizosphere (Ezawa et al 2005). It is not clear how this induced expression could help the fungal symbiont preferentially gain more C from the host.…”

The Role of the Mycorrhizal Symbiosis in Nutrient Uptake of Plants and the Regulatory Mechanisms Underlying These Transport Processes

“…The exploration of large soil volumes by the ERM in which orthophosphate (Pi) is scavenged and delivered to plant cortical cells, bypassing the plant pathway for P uptake [66,67] (Figure 4);  The small hyphal diameter that allows the fungus to penetrate into small soil cores in search for P, and higher P influx rates per surface unit [66,68];  The capability of mycorrhizal fungi to store P in form of polyphosphates, which allows the fungus to keep the internal Pi concentration relatively low, and allows an efficient transfer of P from the ERM to the IRM [69]; and  The production and secretion of acid phosphatases and organic acids that facilitate the release of P from organic complexes [70,71].…”