Characterisation and physical mapping of cyclophilin A genes and identification of new classes of cyclophilins in wheat

Abstract

The cyclophilins, a class of ‘foldase’ enzymes that catalyse the rate-limiting step of peptidyl-prolyl cis–trans isomerization, are up-regulated during wheat endosperm development and suggested to be important for folding of the storage proteins, thus influencing wheat quality. However, little information exists on the types of cyclophilins expressed, the genes encoding these, and their possible functions in wheat endosperm. We have characterised three isoforms of genes encoding cyclophilin A from eight wheat cultivars, using previously isolated cDNAs. The genes are small, intronless, comprise a small multi-gene family, lack any inter-cultivar polymorphisms and localise to chromosomal arms 6AS, 6BS and 6DS, in a region where genes for other quality traits are localised, the locus at 6AS possibly having duplicated genes. Further, cDNAs encoding two novel, endosperm-expressed classes of cyclophilins have been isolated, one being potentially plastid-localised and the other, a nuclear protein with cyclophilin-like domains. In-silico analyses have further led to identification of another form of cyclophilin A and a potentially ER-localised, endosperm-expressed cyclophilin B. The plastid and ER-localised forms are of particular relevance to events occurring during endosperm maturation. The results thus provide valuable data and molecular tools for isolation and analysis of these genes, to address their roles and any association with wheat quality traits.