Analysis of gene expression in arbuscular mycorrhizas: new approaches and challenges

This review summarizes the most recent results obtained using molecular bio logical techniques in the understanding of the arbuscular mycorrhizal symbi osis. On the plant side, cDNA libraries have been established from mycorrhi zal RNA using several techniques, such as suppressive subtractive hybridiza tion, and a large number of clones are being sequenced to obtain expressed sequence tags (ESTs). These ESTs can be transferred to solid supports (arra ys) and hybridized with cDNA from different sources to obtain RNA accumulat ion profiles of genes expressed during the mycorrhizal symbiosis. On the fu ngal side, EST libraries are also being established, both using direct clon ing and suppressive subtractive hybridization techniques. For both partners , the next steps are the detailed analysis of some relevant genes concerned with regulation and function, as well as the study of their role in the sy mbiosis. At the end of this review, we discuss how results about gene expre ssion and functioning from molecular analyses can help in understanding the ecology of the symbiosis and the way in which it can be further exploited for application in plant production systems. (C) New Phytologist (2001) 150 . 517-523.