Isolation by differential display of three partial cDNAs potentially coding for proteins from the VA mycorrhizal Glomus intraradices

A molecular study of the mycorrhizal symbiosis between barley and Glomus in traradices used differential display PCR and a synchronous colonization met hod to identify genes that are differentially expressed in symbiosis. Sever al PCR products were consistently differentially amplified. PCR amplificati on of genomic DNA from either G. intraradices or barley as templates showed that three such products were encoded by G. intraradices. Sequence analysi s of the deduced amino acid sequences of the fungal fragments, following ex tension by 3'-RACE, revealed similarities to proteins from higher eukaryote s. One (GINMYC1) shows similarity to TRIP15, a human protein that interacts in a hormone-dependent manner with the thyroid receptor. A second (GINMYC2 ) is similar to O-linked N-acetylglucosamine transferases from vertebrates, and the third (GINHB1) contains a putative leucine zipper and a homeodomai n which indicates that it binds DNA and may act as a transcriptional regula tor. Fragments of the expected sizes were amplified by RT-PCR from mRNA of mycorrhizal barley roots for all three fungal cDNAs, which indicates that t he corresponding genes are expressed during intraradical growth of G. intra radices. The results provide a promising insight to fungal gene expression early in formation of this compatible and mutualistic symbiosis.