The adaptive response of Egyptian barley land races to drought stress was analyzed using difference gel electrophoresis (DIGE). Physiological measurements and proteome alterations of accession number 15141, drought tolerant, and accession number 15163, drought sensitive, were compared. Differentially expressed proteins were subjected to MALDI-TOF-MS analysis. Alterations in proteins related to the energy balance and chaperons were the most characteristic features to explain the differences between the drought-tolerant and the drought-sensitive accessions. Further alterations in the levels of proteins involved in metabolism, transcription and protein synthesis are also indicated.

Forisomes are protein aggregates found uniquely in the sieve elements of Fabaceaen plants. Upon wounding they undergo a reversible, calcium-dependent conformational switch which enables them to act as cellular stopcocks. Forisomes begin to form in young sieve elements at an early stage of metaphloem differentiation. Genes encoding forisome components could therefore be useful as markers of early sieve element development. Here we present a comprehensive analysis of the developmental expression profile of for1, which encodes such a forisome component. The for1 gene is highly conserved among Fabaceaen species and appears to be unique to this phylogenetic lineage since no orthologous genes have been found in other plants, including Arabidopsis and rice. Even so, transgenic tobacco plants expressing reporter genes under the control of the for1 promoter display reporter activity exclusively in immature sieve elements. This suggests that the regulation of sieve element development is highly conserved even in plants where mature forisomes have not been detected. The promoter system could therefore provide a powerful tool for the detailed analysis of differentiation in metaphloem sieve elements in an unexpectedly broad range of plant species.