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.