The Pisum sativum L. mutant RisNod24 (Pssym36) is defective for arbuscular mycorrhiza formation in late stages of AM. Recent studies identified some plant genes up- and down- regulated at stage of arbuscular development using pea mutant RisNod24, but nothing is still known about fungal gene inactivation. To investigate effect of PsSym36 pea gene on fungal gene expression, Glomus intraradices genes which have been previously identified as markers of successful symbiosis development (Seddas et al., unpublished results) were chosen. List of AM genes used in this study: signalling, transcription, protein turn-over (RHO/GDP dissociation inhibitor, Peptidylprolyl isomerase 2, 26S proteasome subunit 2, 26S proteasome regulatory subunit), lipid metabolism (Stearoyl-CoA desaturase), anit-oxidative metabolism (Thioredoxin peroxidase, Superoxidase dismutase) and unknown function (Hypothetical protein 1). Values were normalized against the constitutively expressed reference gene TEF (Translation elongation factor 1, subunit). Transcript accumulation was monitored by RT-PCR in inoculated roots of pea line Finale (wild type plants) and mutant line RisNod24 (21 day). At 21 day 11,5% root system of RisNod24 and 68,62% root system of Finale were colonized by G. intraradices, root cells of mutant RisNod24 contained few arbuscule only. All fungal genes, except gene with unknown function (Hypothetical protein 1), were strongly down-regulated in RisNod24 in comparison with wild type line Finale. Obtained date confirm hypothesis that palnt genotype influence on AM fungal gene activity. G. intraradices genes of transcription, protein turn-over (RHO/GDP dissociation inhibitor, Peptidylprolyl isomerase 2, 26S proteasome subunit 2, 26S proteasome regulatory subunit), lipid metabolism (Stearoyl-CoA desaturase) and anti-oxidative metabolism (Thioredoxin peroxidase, Superoxidase dismutase) were down-regulated in pea arbuscular-defective mutant RisNod24 (Pssym36) in comparison with wild type line Finale. This research was performed in collaboration with laboratory ‘Plant-Microbe-Environment’ (UMR INRA 1088/CNRS 5184/Université de Bourgogne PME) and financially supported by French embassy in Moscow, Department of Science, Technology and Space and grants RFBR (07-04-01558, 07-04-01171).