Date of Award
Doctor of Philosophy (PhD)
Biochemistry and Molecular Biology
Smith , Kerry S
Moore , Brandon M
Dominy , Brian N
South Carolina and Georgia are the largest peach producing regions in the Southeastern United States, generating about $60 million worth (~90,000 tons) of fruit per year on average. Peaches and other stone-fruits (Prunus sp.) can be afflicted by a variety of root-associated diseases which negatively impact annual yield and long-term tree mortality. An engineered Prunus rootstock with enhanced resistance to soil-borne pathogens would therefore be of great benefit to the Southeastern peach industry. The Gastrodia anti-fungal protein (GAFP) is a monocot mannose-binding lectin which is able to inhibit the growth of multiple species of plant pathogenic fungi. Previous findings from our lab demonstrated that GAFP-1 expression in tobacco resulted in increased tolerance to infection by the stramenopile, root-knot nematode (RKN), and fungal pathogens Phytophthora nicotianae, Meloidogyne incognita, and Rhizoctonia solani, respectively. Further work in transgenic plum suggested that expression of GAFP-1 was also able to impart protective effects against the stramenopile, P. cinnamomi, and the RKN M. incognita, in a Prunus species. GAFP-1 purified from tobacco directly inhibited the mycelium of P. cinnamomi and P. nicotianae in a concentration dependent manner in vitro. Contact with the lectin, however, did not impair J2 mobility or egg hatch in M. incognita over 96 h. GAFP-1 strongly associated with the cell wall pellets prepared from P. cinnamomi and the fungus Trichoderma viride, providing evidence that GAFP-1 can bind cell wall components of a stramenopile pathogen as it has been hypothesized to do in fungi. Neither gafp-1 transcripts nor the GAFP-1 lectin were detected within non-transformed plum tissues grafted to transgenic plum rootstocks after two years, suggesting that tissue expressing the lectin may be able to retain the foreign gene products so that they will not enter the fruit where they could potentially be consumed. Future plans include multi-year disease trials with transgenic plum lines against fungal and non-fungal pathogens, monitoring of chimeric-grafted plants for the possible accumulation of GAFP-1 in non-transformed tissues after seasonal changes in the field, and further investigation into the mechanism of a lectin which has great potential for agricultural application.
Nagel, Alexis, "Understanding GAFP, A Plant Lectin with Broad Spectrum Inhibitory Activity" (2010). All Dissertations. 621.