Biomedical subjects

Craig Richael

Publications and source records attributed to Craig Richael.

3 recordsLinked to original sources

PubMed2006

Improving potato storage and processing characteristics through all-native DNA transformation.

The dominant potato (Solanum tuberosum) variety for French fry production in the United States is the 131-year-old Russet Burbank. Market penetration of the higher yielding and more uniform Ranger Russet variety is limited to about one-fifth of that of the Russet Burbank because of two storage deficits: black spot bruise sensitivity and high levels of cold-induced sweetening. Here, these trait weaknesses are turned into strengths by simultaneously lowering the expression of Ranger Russet's tuber-expressed polyphenol oxidase (Ppo), starch-associated R1, and phosphorylase-L (PhL) genes. This genetic modification was accomplished without inserting any foreign DNA into the plant genome. French fries from the intragenic potatoes also contained reduced amounts of the antinutritional compound acrylamide while, unexpectedly, displaying enhanced sensory characteristics.

DNA, Plant↗

PubMed2004

Crop improvement through modification of the plant's own genome.

Plant genetic engineering has, until now, relied on the incorporation of foreign DNA into plant genomes. Public concern about the extent to which transgenic crops differ from their traditionally bred counterparts has resulted in molecular strategies and gene choices that limit, but not eliminate, the introduction of foreign DNA. Here, we demonstrate that a plant-derived (P-) DNA fragment can be used to replace the universally employed Agrobacterium transfer (T-) DNA. Marker-free P-DNAs are transferred to plant cell nuclei together with conventional T-DNAs carrying a selectable marker gene. By subsequently linking a positive selection for temporary marker gene expression to a negative selection against marker gene integration, 29% of derived regeneration events contain P-DNA insertions but lack any copies of the T-DNA. Further refinements are accomplished by employing Omega-mutated virD2 and isopentenyl transferase cytokinin genes to impair T-DNA integration and select against backbone integration, respectively. The presented methods are used to produce hundreds of marker-free and backbone-free potato (Solanum tuberosum) plants displaying reduced expression of a tuber-specific polyphenol oxidase gene in potato. The modified plants represent the first example of genetically engineered plants that only contain native DNA.

Base Sequence↗

PubMed2002

Expression of the antiapoptotic baculovirus p35 gene in tomato blocks programmed cell death and provides broad-spectrum resistance to disease.

The sphinganine analog mycotoxin, AAL-toxin, induces a death process in plant and animal cells that shows apoptotic morphology. In nature, the AAL-toxin is the primary determinant of the Alternaria stem canker disease of tomato, thus linking apoptosis to this disease caused by Alternaria alternata f. sp. lycopersici. The product of the baculovirus p35 gene is a specific inhibitor of a class of cysteine proteases termed caspases, and naturally functions in infected insects. Transgenic tomato plants bearing the p35 gene were protected against AAL-toxin-induced death and pathogen infection. Resistance to the toxin and pathogen co-segregated with the expression of the p35 gene through the T3 generation, as did resistance to A. alternata, Colletotrichum coccodes, and Pseudomonas syringae pv. tomato. The p35 gene, stably transformed into tomato roots by Agrobacterium rhizogenes, protected roots against a 30-fold greater concentration of AAL-toxin than control roots tolerated. Transgenic expression of a p35 binding site mutant (DQMD to DRIL), inactive against animal caspases-3, did not protect against AAL-toxin. These results indicate that plants possess a protease with substrate-site specificity that is functionally equivalent to certain animal caspases. A biological conclusion is that diverse plant pathogens co-opt apoptosis during infection, and that transgenic modification of pathways regulating programmed cell death in plants is a potential strategy for engineering broad-spectrum disease resistance in plants.

Apoptosis↗