Characterization and expression of dehydrins in wild Egyptian pea (Pisum sativum L.)
Pea genotypes exhibited significant genetic variation in drought tolerance. Polymerase chain reaction (PCR) screening for dehydrins in different pea genotypes indicated the amplification of at least six dehydrin gene fragments varied in length from 500 to 1000 bp. In this study, a dehydrin gene, PsDhn1 (GenBank accession number JN182234), was isolated and characterized from wild Egyptian pea (Pisum sativum L.) using specific PCR. It belongs to the Y2K2 dehydrin subclass induced by drought stress. DNA sequence indicated an open reading frame which predicts a protein with 196 amino acids and molecular mass of about 21 kDa. Deduced amino acid sequence indicated the presence of the N-terminal consensus motif, Y-segment D(E/Q)YGNP, and the lysine rich domain, K-segment KIKEK(I/L)PG, common for all dehydrins, both of which are present in two copies. However, it lacks the track of serine residues (S-segment). Egyptian pea dehydrin (PsDHN1) contains two copies of a semi-conserved sequence of six amino acid residues in length (EYVREE), which lie in front of the lysine rich motif (K-segment), and common only for pea dehydrins. Northern blot analysis indicated two dehydrin mRNA transcripts detectable by PsDhn1 probe. Western blot analysis using anti-dehydrin polyclonal antibody detected two corresponding dehydrins (29 and 21 kDa) accumulated in developing pea cotyledons. Both mRNA transcripts and dehydrins showed different patterns of expression and accumulation. The amino acid composition of dehydrins with high content of charged and polar residues may promote their specific protective functions under conditions of cell dehydration.
Key words: Dehydrins, late embryogenesis abundant (LEA) genes, drought tolerance, pea, desiccation.