Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/16/2002
Publication Date: N/A
Interpretive Summary: Under the Low Input Sustainable Agricultural (LISA) program, new , more efficient, methods of growing food crops with lower inputs of fertilizers and pesticides are presently being evaluated. One important means for achieving this goal is through the development of a plant/microbe symbiotic system known as arbuscular mycorrhizas (AM), whereby a low concentration of fwidely dispersed nutrients can be efficiently delivered from the soil to the growing plant. In addition the association of such microorganisms or fungi impart disease resistance to the plant making the need for pesticide application considerably lower. Ideally, one would want to inoculate fields with such beneficial organisms ("biofertilizers") to facilitate the LISA approach to food production, however, since these organisms are presently obligate symbionts they can only be grown in association with the host plant. This limits our ability to make large quantities of pure cultures of these fungi needed for field inoculation. In this study we determined the genes that are expressed in the fungus during a critical stage of the symbiotic life cycle. This information has revealed what biochemical pathways are required to be activated in order to establish a pure fungal culture.
Technical 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. Codon utilization in G. intraradices was found to be similar to G. mosseae but to be very different from G. versiforme. 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.