A genomics approach towards salt stress tolerance

Abiotic stresses reduce plant productivity. We focus on gene expression analysis following exposure of plants to high salinity, using salt-shock experiments to mimic stresses that affect hydration and ion homeostasis. The approach includes parallel molecular and genetic experimentation. Comparative analysis is employed to identify functional isoforms and genetic orthologs of stress-regulated genes common to cyanobacteria, fungi, algae and higher plants. We analyze global gene expression profiles monitored under salt stress conditions through abundance profiles in several species: in the cyanobacterium Synechocystis PCC6803, in unicellular (Saccharomyces cerevisiae) and multicellular (Aspergillus nidulans) fungi, the eukaryotic alga Dunaliella salina, the halophytic land plant Mesembryanthemum crystallinum, the glycophytic Oryza sativa and the genetic model Arabidopsis thaliana. Expanding the gene count, stress brings about a significant increase of transcripts for which no function is known. Also, we generate insertional mutants that affect stress tolerance in several organisms. More than 400 000 T-DNA tagged lines of A. thaliana have been generated, and lines with altered salt stress responses have been obtained. Integration of these approaches defines stress phenotypes, catalogs of transcripts and a global representation of gene expression induced by salt stress. Determining evolutionary relationships among these genes, mutants and transcription profiles will provide categories and gene clusters, which reveal ubiquitous cellular aspects of salinity tolerance and unique solutions in multicellular species. (C) 2001 Editions scientifiques et medicales Elsevier SAS.