A microarray carrying 5,648 probes of Medicago truncatula root-expressed genes was screened in order to identify those that are speciWcally regulated by the arbuscular mycorrhizal (AM) fungus Gigaspora rosea, by P i fertilisation or by the phytohormones abscisic acid and jasmonic acid. Amongst the identiWed genes, 21% showed a common induction and 31% a common repression between roots fertilised with P i or inoculated with the AM fungus G. rosea, while there was no obvious overlap in the expression patterns between mycorrhizal and phytohormonetreated roots. Expression patterns were further studied by comparing the results with published data obtained from roots colonised by the AM fungi Glomus mosseae and Glomus intraradices, but only very few genes were identiWed as being commonly regulated by all three AM fungi. Analysis of P i concentrations in plants colonised by either of the three AM fungi revealed that this could be due to the higher P i levels in plants inoculated by G. rosea compared with the other two fungi, explaining that numerous genes are commonly regulated by the interaction with G. rosea and by phosphate. DiVerential gene expression in roots inoculated with the three AM fungi was further studied by expression analyses of six genes from the phosphate transporter gene family in M. truncatula. While MtPT4 was induced by all three fungi, the other Wve genes showed diVerent degrees of repression mirroring the functional diVerences in phosphate nutrition by G. rosea, G. mosseae and G. intraradices.

Suppressive subtractive hybridisation was applied to the analysis of late stage arbuscular mycorrhizal development in pea. 96 cDNA clones were amplified and 81, which carried fragments more than 200 nt in size, were sequence analysed. Among 67 unique fragments, 10 showed no homology and 10 were similar to sequences with unknown function. RNA accumulation of the corresponding 67 genes was analysed by hybridisation of macro-arrays. The cDNAs used as probes were derived from roots of wild type and late mutant pea genotypes, inoculated or not with the AM fungus Glomus mosseae. After calibration, a more than 2.5-fold mycorrhiza-induced RNA accumulation was detected in two independent experiments in the wild type for 25 genes, 22 of which seemed to be induced specifically during late stage AM development. Differential expression for 7 genes was confirmed by RT-PCR using RNA from mycorrhiza and from controls of a different pea cultivar. In order to confirm arbuscule-related expression, the Medicago truncatula EST data base was screened for homologous sequences with putative mycorrhiza-related expression and among a number of sequences with significant similarities, a family of trypsin inhibitor genes could be identified. Mycorrhiza-induced RNA accumulation was verified for five members by real-time PCR and arbuscule-related activation of the promoter could be shown in transgenic roots for one of the genes, MtTi 1.

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Biochemistry Z 0250Gene Expression Analysis of Arbuscule Development and Functioning -[ca. 70 refs.]. -(FRANKEN*, P.; DONGES, K.; GRUNWALD, U.; KOST, G.; REXER, K.-H.; TAMASLOUKHT, M.; WASCHKE, A.; ZEUSKE, D.; Phytochemistry 68 (2007) 1, 68-74; Inst. Veg. Ornamental Crops, D-14979 Grossbeeren, Germany; Eng.) -Lindner 23-267