Convicilin mRNA from pea (Pisum sativum L.) has sequence homology with other legume 7S storage protein mRNA species

Isolation and characterization of Korean pine (Pinus koraiensis) convicilin

A vicilin-like globulin seed storage protein, termed convicilin, was isolated for the first time from Korean pine (Pinus koraiensis). SDS-PAGE analysis revealed that Korean pine convicilin was post-translationally processed. The N-terminal peptide sequences of its components were determined. These peptides could be mapped to a protein translated from an embryo abundant transcript isolated in this study. Similar to vicilin, native convicilin appeared to be homotrimeric. Differential scanning calorimetry (DSC) analyses revealed that this protein is less resistant to thermal treatment than Korean pine vicilin. Its transition temperature was 75.57 °C compared with 84.13 °C for vicilin. The urea induced folding-unfolding equilibrium of pine convicilin monitored by intrinsic fluorescence could be interpreted in terms of a two-state model, with a Cm of 4.41 ± 0.15 M.

Another class of vicilin gene in Pisum

We describe a novel class of vicilin gene in Pisum corresponding to a precursor polypeptide of Mr 68000. The mRNA corresponding to this polypeptide accumulates during seed development in a pattern similar to that of convicilin. Hybridization and sequence analyses show that this vicilin gene class is less homologous to other Pisum vicilin gene classes than these last are to each other. Gene-copy-number estimates and decreased stringency hybridizations of the gene class described here show that the Pisum vicilin gene family is bigger and more complex than hitherto reported.

Pea convicilin: structure and primary sequence of the protein and expression of a gene in the seeds of transgenic tobacco

Convicilin, a trimeric globulin of pea (Pisum sativum L.) seeds, is closely related to vicilin and composed of polypeptides of 68.2 kilodaltons. A partial copy DNA (cDNA) clone encoding convicilin was isolated, sequenced, and used to select a convicilin gene from a pea genomic library. A part of the genomic clone was sequenced to obtain the coding sequences missing in the cDNA clone and a further 1 kilobase 5' to the start of transcription were also obtained. The entire sequence of convicilin was deduced from the combined genomic and cDNA sequences. The complete gene encoding convicilin was transferred to tobacco (Nicotiana tabacum L.) and the characteristics of its expression in the seeds of transgenic plants were studied. An unprocessed polypeptide, which was found only in the seeds of the transgenic plants, was identical in size to pea convicilin, and was recognized by vicilin antibodies. Convicilin, which does not undergo posttranslational cleavage in peas, was partially processed to polypeptides of a relative molecular mass (Mr) of approx. 50000 in transgenic tobacco seeds. There was a twofold variation in the level of convicilin accumulated by the mature seeds of a number of transgenic plants and this was well correlated with the number of gene copies incorporated in the different transformants. In the seeds of tobacco plants that contained a single copy of the transferred gene it was estimated that convicilin comprised up to 2% of the seed protein. Thus, using a combination of gene sequencing and expression in a heterologous host we believe we have characterized the gene corresponding to theCvc locus, whereas the gene described by D. Bown et al. (1988, Biochem J.,251, 717-726) probably encodes a minor convicilin-related protein.

The sequence of a gene encoding convicilin from pea (Pisum sativum L.) shows that convicilin differs from vicilin by an insertion near the N-terminus

The sequence of a gene encoding convicilin, a seed storage protein in pea (Pisum sativum L.), is reported. This gene, designated cvcA, is one of a sub-family of two active genes. The transcription start of cvcA was mapped. Convicilin genes are expressed in developing pea seed cotyledons, with maximum levels of the corresponding mRNA species present at 16-18 days after flowering. The gene sequence shows that convicilin is similar to vicilin, but differs by the insertion of a 121-amino-acid sequence near the N-terminus of the protein. This inserted sequence is very hydrophilic and has a high proportion of charged and acidic residues; it is of a similar amino acid composition to the sequences found near the C-terminal of the alpha-subunit in pea legumin genes, but is not directly homologous with them. Comparison of this sequence with the 'inserted' sequence in soya-bean (Glycine max) conglycinin (a homologous vicilin-type protein) suggests that the two insertions were independent events. The 5' flanking sequence of the gene contains several putative regulatory elements, besides a consensus promoter sequence.

Measurement of gene number for seed storage proteins in Pisum

We have measured the numbers of genes coding for the three seed storage proteins, vicilin, convicilin and legumin, in a number of Pisum genotypes of variant protein composition. No difference in gene number existed among P. sativum genotypes for any of the proteins. There were differences in the number of genes coding for individual proteins with approximately 11 genes (per haploid genome) for vicilin, 8 genes for legumin and 1 gene for convicilin.