Skip to main content
ARS Home » Research » Publications at this Location » Publication #117481
Title: ANALYSIS OF INSECTICIDAL ACTIVITY IN TRANSGENIC PLANTS CARRYING THE IPT PLANT GROWTH HORMONE GENE

Author
item Smigocki, Anna
item HEU, SUNGGI - SOUTH KOREA
item BUTA, GEORGE - RETIRED

Submitted to: Acta Physiologiae Plantarum
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/8/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: Insect infestations of major economic U.S. crops inflict economically devastating losses to farmers. Novel approaches are needed to combat these losses in an environmentally safe fashion. There is particular need to understand mechanisms of plant resistance to insects. We investigated a gene that is responsible for the synthesis of a plant growth regulator (cytokinin) to understand its role in enhancing plant resistance to insects. We introduced this gene into tobacco plants by methods of biotechnology. The results showed that introduction of this gene increased the level of insecticidal materials in the plants and increased the resistance of the plants to tobacco hornworm and aphids. The findings will be useful to scientists in efforts to understand plant resistance to insects and in efforts to enhance this resistance.

Technical Abstract: The expression of a bacterial cytokinin biosynthesis gene (PI-II-ipt) in Nicotiana plumbaginifolia Viviani plants has been correlated with enhanced resistance to Manduca sexta and Myzus persicae. We expressed the PI-II-ipt gene in N. tabacum and Lycopersicon esculentum and observed similar antifeedent effects with the transgenic tobacco but not tomato. A 30 to 50% reduction in larval weight gain was observed with some of the tomato plants but these results could not be repeated consistently. Leaf surface extracts from transgenic N. plumbaginifolia leaves killed l00% of M. sexta second instars at concentrations of 0.05% (w/v) whereas the N. tabacum extracts were at least 20 times less active. Extract suspensions were stable for up to 2 days at ambient temperatures below 42oC and for at least 3 months at 4oC when stored in the dark. HPLC analysis of the N. plumbaginifolia extracts yielded an active fraction that reduced hatching of M. sexta eggs by 30% and killed first, second and third instars within 24, 48 and 72 hours of exposure, respectively. The activity appears to be associated with oxygen-containing aliphatic compounds, possibly diterpenes, as analyzed by TLC, UV absorption and fragmentation with EIMS. Based on the partial characterization of this activity, the production, secretion or accumulation of secondary metabolites in leaves of cytokinin producing PI-II-ipt N. plumbaginifolia plants appears to be responsible for the observed insect resistance.