Characterization of salt tolerance in poplar

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In the genus Populus, P. euphratica is outstanding with respect to its salt tolerance but also for its slow growth. Salt stress leads to anatomical changes in wood structure. Since the degree of salt tolerance is furthermore age-dependent, this model offers the possibility to study age-related functions as well as structural adaptation to stress. The goal of this proposal is to characterize the salt tolerant tree Populus euphratica in comparison with the salt sensitive Populus x canescens. Since we found that salt treatment also affected the differentiation of roots and triggered production of H2O2, our working hypothesis is that salinity induces changes in differentiation via disturbance of the cellular redox state and/or effects on ion homeostasis. We plan to analyze H2O2 production in relation to salt-induced changes in stem anatomy. Transcriptional profiling of salinity-induced genes of the cambium in relation to oxidant formation and developmental changes in poplar will be performed. In the context of salt tolerance ion homeostasis is important. We have cloned two cDNAs coding for different putative Na+/H+ antiporters from P. euphratica. These antiporters will be characterized at the gene and protein level and their expression will be compared with changes in the subcellular localisation and concentration of Na+/K+ in the cambium under salt stress in relation to tree age.