Isolation and Characterization of Endomycorrhizal Fungi Associated with Growth Promotion of Blueberry Plants

Abstract

Despite their notable root mutualism with blueberries (<i>Vaccinium</i> spp.), studies related to Ericoid mycorrhizal (ERM) are relatively limited. In this study, we report the isolation of 14 endomycorrhizal fungi and their identification by fungal colony morphology characterization combined with PCR-amplified fungal internal transcribed spacer (ITS) sequence analyses. Six of the isolated strains were confirmed as beneficial mycorrhizal fungi for blueberry plants following inoculation. We observed the formation of typical ERM hyphae coil structures-which promote and nutritionally support growth-in blueberry seedlings and significant nitrogen and phosphorous content increases in diverse tissues. QRT-PCRs confirmed changes in <i>VcPHT1s</i> expression patterns. After the formation of ERM, <i>PHT1-1</i> transcription in roots was upregulated by 1.4- to threefold, whilst expression of <i>PHT1-3</i> and <i>PHT1-4</i> in roots were downregulated 72% and 60%, respectively. Amino acid sequence analysis of all four <i>VcPHT1s</i> genes from the blueberry variety "Sharpblue" revealed an overall structural similarity of 67% and predicted transmembrane domains. Cloning and overexpression of <i>PHT1-1</i> and <i>PHT1-3</i> genes in transgenic <i>Arabidopsis thaliana</i> plants significantly enriched total phosphorus and chlorophyll content, confirming that <i>PHT1-1</i> and <i>PHT1-3</i> gene functions are associated with the transport and absorption of phosphorus.