Molecular characterization of Cyclophilin B genes and promoter sequences in wheat and rice

The storage proteins (prolamins) of wheat endosperm are commonly grouped into the monomeric gliadins and polymeric glutenins, the latter comprised of low and high molecular weight (LMW and HMW) subunits1, 2. This forms the highly structured protein network (gluten) that determines the viscoelastic properties of the flour which affect its end-uses1, 2, 3. The storage protein bonding, folding, assortment and deposition processes in the endosperm imply significant roles for ER-localised chaperones and ‘foldase’ enzymes, and three groups of proteins are likely involved: the enzymes protein disulphide isomerases (PDI), peptidyl-prolyl cis-trans isomerases (PPIases), and the Binding Protein (BiP)/heat shock protein (Hsp70) chaperones4, 5. The cyclophilins (CyPs), belonging to PPIase class, are of particular interest as preliminary evidence shows their involvement in seed storage protein processes6, 7. The ER-localised Cyps (commonly called CypB) are of particular relevance due to the storage protein folding and assortment processes for both transport pathways initiating and/or occurring in the ER. However, little genetic information exists on genes encoding this ‘foldase’ enzyme, and on the flanking regulatory sequences which might affect the timing, tissue specificity or transcription rates. This work reports on the CypB genes and their promoters in wheat.