BENABDELLAH, KARIM, CONCEPCION AZCÓN-AGUILAR & NURIA FERROL.
Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, CSIC, Profesor Albareda 1, 18008 Granada, SPAIN.
Understanding the molecular and genetic bases of the plant-fungus interaction in a functional arbuscular mycorrhizal (AM) symbiosis requires the identification of genes and gene products involved in this process. In the present work we have used 2D-PAGE, a useful technique for the global analysis of cellular gene expression, to investigate the effect of AM colonization upon tomato gene expression. Comparison of 2D-PAGE patterns of total, soluble, microsomal and plasma membrane proteins isolated from mycorrhizal and non-mycorrhizal tomato roots showed that, in all these fractions, AM colonization induced three major changes in tomato root gene expression: up-regulation and down regulation of some constitutive polypeptides already present in tomato roots and induction of some new polypeptides or endomycorrhizines. Although only nine differentially displayed polypeptides were detected in total protein extracts, fractionation into soluble, microsomal and plasma membrane proteins allowed to identify a much greater number of differentially regulated polypeptides in tomato roots as a consequence of AM symbiosis. These data indicate that during mycorrhizal development the expression of some polypeptides is changed in such a low level, that it is necessary to further purify the root extract in order to detect these changes. Polypeptide patterns of AM roots have been also compared with those of the extraradical mycelium of Glomus mosseae to discriminate between the newly-induced polypeptides and polypeptides from the fungal partner. At this stage of research we do not know the role of the differentially displayed polypeptides, but we are currently developing methods for the N-terminal sequencing of some of them.