Hugh S. Mason

Oral immunization with a recombinant bacterial antigen produced in transgenic plants

The binding subunit of Escherichia coli heat-labile enterotoxin (LT-B) is a highly active oral immunogen. Transgenic tobacco and potato plants were made with the use of genes encoding LT-B or an LT-B fusion protein with a microsomal retention sequence. The plants expressed the foreign peptides, both of which formed oligomers that bound the natural ligand. Mice immunized by gavage produced serum and gut mucosal anti-LT-B immunoglobulins that neutralized the enterotoxin in cell protection assays. Feeding mice fresh transgenic potato tubers also caused oral immunization.

Generation of transgenic banana (Musa acuminata) plants via Agrobacterium-mediated transformation

An Agrobacterium-mediated plant transformation system was developed for the generation of transgenic banana (Musa spp. van Grand Nain). This system allowed for the recovery of putative transformants within four weeks after co-cultivation of tissue samples with Agrobacterium. Two or more cycles of meristem rooting and micropropagation allowed for the selection of plants from this putative transformant population which demonstrated chromosomal integration of foreign DNA by Southern analysis with no indication of chimeric tissues. Since plant breeding strategies aimed at banana crop improvement are extremely complex and long-term, virtually all commercial production is from clonal derivatives of naturally occurring variants. The genetic transformation technology reported herein will provide an additional tool for crop breeders who wish to introduce value-added traits into the banana and plantain cultivars that serve as vital food sources and a means of generating export income for producing nations.

Proteins homologous to leaf glycoproteins are abundant in stems of dark-grown soybean seedlings. Analysis of proteins and cDNAs

We report here the cloning and sequence analysis of cDNAs for a pair of closely related proteins from soybean (Glycine max [L.] Merr. cv. Williams 82) stems. Both proteins are abundant in soluble extracts of seedling stems but not of roots. One of these proteins (Mr=28 kDa) is also foundd in the cell wall fraction of stems and actumulates there when seedlings are exposed to mild water deficit for 48 h. The mRNA for these proteins is most abundant in the stem region which contains dividing cells, less abundant in elongating and mature stem cells, and rare in roots. Using antiserum against the 28 kDa protein, we isolated cDNA clones encoding it and an antigenically related 31 kDa protein. The two cDNAs are 80% homologous in nucleotide and amino acid coding sequence. The predicted proteins have similar hydropathy profiles, and contain putative NH2-terminal signal sequences and a single putative N-linked glycosylation site. The two proteins differ significantly in calculated pI (28 kDa=8.6; 31 kDa=5.8), and the charge difference is demonstrated on two-dimensional gels. The proteins described here may function as somatic storage proteins during early seedling development, and are closely related to glycoproteins which accumulate in vacuoles of paraveinal mesophyll cells of fully expanded soybean leaves when plants are depodded.