Characterisation of a methionine-rich storage protein cDNA from perilla (Perilla frutescens) seeds

We have cloned and characterised a cDNA (PrLeg) coding for a methionine-rich storage protein, which is reported for the first time in perilla (Perilla frutescens (L.) Britt. var. Japonica) seeds, homologous to the 11S legumin-like storage proteins. The most significant feature of the PrLeg precursor protein is that it has the highest content of methionine residues among the 11S legumin-like storage proteins examined so far. Another feature is that the deduced amino acid sequences of the PrLeg protein are phylogenetically close to the sequence groups derived from evolutionally ancient states of the 11S legumin-like storage proteins, or from gymnospermous seed storage proteins, such as Magnolia, Asarum, Dioscorea, Cryptomeria, Metasequoia and Ginkgo. In contrast, with the exception of sesame, relatively low phylogenetic relationships are determined between the PrLeg sequence group and those derived from crop plants, such as soybean, pea, broad bean, rape, pumpkin, rice, coffee and citrus. Southern blot analysis suggests that there may be several copy numbers of thePrLeg genes and their seed-specific expression patterns at the transcriptional level were confirmed by northern hybridisation analysis.