Isolation bydifferential display of three cDNAs coding for proteins from the VAmycorrhizal fungus G. intraradices

DELP, GABRIELE¹, SUSAN J. BARKER¹ & SALLY E. SMITH².

¹Department of Plant Science and ²Department of Soil Science, University of Adelaide, WaiteCampus, Glen Osmond, SA 5064, AUSTRALIA.

In our molecular study of the mycorrhizal symbiosis between barleyand Glomus intraradices we are using differential display to identify genes that are differentially expressed in mycorrhizal roots. Using roots with uniform infection stages produced by a nurse pot method, several PCR products derived from both mycorrhizal and control root mRNAwere consistently differentially amplified. PCR with fragment-specific primers using G. intraradices and barley DNAs as templates showed that two were of plant origin, three were encoded by G. intraradices. Sequence analysis of the fungal fragments revealed homologies to genes from higher eucaryotes: one (dd5) shows homology to trp 15, a human protein that interacts in a hormone-dependant manner with the thyroid receptor, andAlien, a developmentally regulated Drosophila melanogaster protein, the second (dd10) is similar toO-GlcNAc transferases from vertebrates, and the third one (dd11) contains a homeobox and a Leucine zipper, which indicates that it could interact with other proteins and binds DNA, features commonly found in transcriptional regulators. Using specific primers for the fungal differential display products, fragments of the expected size scan be amplified from mRNA of infected but not uninfected barley roots for all three, which indicates that thecorresponding genes are expressed during intraradical growth of G. intraradices. Our results show that differential display is a suitable technique to obtain cDNA sequences from fungal genes that are expressed during VAmycorrhizal interaction.