VTC proteins of arbuscular mycorrhizal fungi

Polyphosphate polymerizing and depolymerizing reactions of VTC4 protein in an arbuscular mycorrhizal fungus

Arbuscular mycorrhizal (AM) fungi form symbiotic associations with land plants and supply soil minerals including phosphorus to their hosts. AM fungi accumulate polyphosphate (polyP), a linear phosphate polymer, in their mycelia, which functions in phosphorus storage and translocation. In the budding yeast Saccharomyces cerevisiae, it has been demonstrated that the vacuolar transporter chaperone 4 (VTC4) protein, a subunit of the VTC complex, is responsible for polyP synthesis. Here, we conducted a comprehensive survey of VTC proteins in AM fungal genomes. The genomes of eight AM fungal species encode VTC1, VTC2, and VTC4.

Methods
Amino acid sequences of AM fungal VTCs were obtained by blastp searches using protein queries from S. cerevisiae (https://www.yeastgenome.org) against AM fungal genome databases. Amino acid sequences were aligned using ClustalW with some manual adjustment. Maximum-likelihood tree inference and bootstrapping with 100 replicates was performed with RAxML-NG version 1.0.1 (Kozlov et al., 2019) using the LG+I+G amino acid substitution model. The best-fitted evolutionary model was identified using ModelTest-NG version 0.1.3 (Darriba et al., 2020). A tree was visualized and annotated with the iTOL platform version 5.7 (Letunic & Bork, 2019).