Protein analysis during almond embryo development. Identification and characterization of a late embryogenesis abundant protein

The expression pattern of proteins was analysed during late embryogenesis in almond (Prunus amygdalus) to obtain information on the molecular events leading to the acquisition of the embryo desiccation tolerance. Analysis of the ABA content in developing embryos revealed high levels at 50 DAF with a rapid decrease at the onset of desiccation. Two-dimensional electrophoresis of proteins showed that at least ten different polypeptides were induced by dehydration of the embryos. By immunoscreening of a mature embryo cDNA expression library, the ABA inducible Parab21 cDNA (for P. amygdalus responsive to ABA) encoding for a highly phosphorylated protein was isolated and characterized. Parab21 belongs to the LEA-D11 protein family, and contains all the protein motifs characteristic for the RAB/dehydrin group of proteins. The Parab21 mRNA is expressed during late embryogenesis and is also inducible by water deficit and ABA treatment in vegetative tissues. Southern blotting and mapping data are consistent with a single Parab21 gene in the almond genome although other immunologically-related proteins have been detected suggesting that a complex family of RAB/dehydrin-related genes will be involved in desiccation tolerance in almonds.