Plant and Soil 244: 141–148, 2002. © 2002 Kluwer Academic Publishers. Printed in the Netherlands. 141 Expression in an arbuscular mycorrhizal fungus of genes putatively involved in metabolism, transport, the cytoskeleton and the cell cycle Jeongwon Jun 1 , Jehad Abubaker 1 , Charles Rehrer 1 , Philip E Pfeffer 2 , Yair Shachar-Hill 1,3 & Peter J Lammers 1 1 Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, NM 88001, USA. 2 USDA- ARS, ERRC, 600 East Mermaid Lane, Wyndmoor, PA 19038, USA. 3 Corresponding author ∗ Received 21 August 2001. Accepted in revised form 16 May 2002 Key words: Arbuscular mycorrhiza, cell cycle, cytoskeleton, meiosis, gene expression, metabolism, transport Abstract Arbuscular mycorrhizal (AM) fungi are multinucleate, coenocytic, obligate symbionts with no known sexual stages and very wide host and habitat ranges. While contributing vitally to the growth of land plants they face unique challenges in metabolism, transport, growth and development. To provide clues to the strategies that AM fungi have adopted, random sequencing of cDNA’s from Glomus intraradices was undertaken. Putative genes for enzymes, transporters, structural proteins and cell-cycle regulatory factors were discovered. Among the EST’s of particular interest are sequences with homology to known trehalase, arsenite transporter, cysteine synthase, tubulins, actin, dynein, cell cycle regulatory proteins, and three meiosis-related proteins. The significance of these sequences is discussed in the context of what is known about AM metabolism, transport, growth and phylogeny. Abbreviations: AM – Arbuscular Mycorrhizal; copy DNA; EST – Expressed sequence tag; NMR – Nuclear Magnetic Resonance; GBA – GenBank Accession Introduction Arbuscular mycorrhizal (AM) fungi lead a biologic- ally unique life style. As multinucleate, coenocytic, obligate symbionts with no known sexual stages and extraordinary host and habitat ranges they face un- usual biological challenges. They therefore present a fascinating opportunity to examine fundamental biological mechanisms. Three areas of cellular and physiological biology invite particular scrutiny be- cause they are very probably uniquely adapted in the AM fungi. These are metabolism and transport, cell cycle regulation and signaling, and structure and morphogenesis. The study of the arbuscular mycorrhizal symbiosis has been hindered in the past by the small amounts of ∗ FAX No.: +1-240-352-8021. E-mail: yairhill@nmsu.edu fungal tissue that are generally available, by the fact that AM fungi are obligate symbionts and by the con- founding influence of other microorganisms present in field or greenhouse-grown mycorrhizal systems. The emergence of in vitro cultures (Becard and Fortin, 1988; St-Arnaud et al., 1996) and the application of molecular biological tools have greatly expanded the range of analyses that are possible (see Harrison, 1999; and Harrier, 2001 for reviews). Here we present some of our recent findings of putatively expressed genes that are related to the three areas of interest identified above. Studies of AM metabolism have included analyt- ical determination of metabolites, enzymatic assays of individual metabolic steps, microscopy and labeling with radioactive and stable isotopes (for review see Bago et al., 2000). From the literature and our own NMR based studies we have proposed working models of carbon and nitrogen metabolism (Bago et al., 2000; Bago et al., 2002). To test and extend this model, and