Cytokinin-mediated insect resistance in Nicotiana plants transformed with the ipt gene

Abstract

The bacterial isopentenyl transferase (ipt) gene involved in cytokinin biosynthesis was fused with a promoter from the proteinase inhibitor II (PI-IIK) gene and introduced into Nicotiana plumbaginifolia. Transcripts of the ipt gene were wound-inducible in leaves of transgenic PI-II-ipt plants. In leaf disks excised from fully expanded leaves, transcript levels increased 25- to 35-fold within 24 h and by 48 h were reduced by about 50%. In flowering plants, message levels were 2- to 5-fold higher than in preflowering plants. These plants were used to test for defensive properties of cytokinins against insects. Manduca sexta larvae consumed up to 70% less of the PI-II-ipt leaf material on flowering plants than larvae feeding on controls. Normal development of Myzus persicae nymphs was also delayed. Approximately half as many nymphs reached adulthood on PI-II-ipt leaves than on controls. Zeatin and zeatinriboside levels in leaves remaining on PI-II-ipt plants after hornworm feeding were elevated by about 70-fold and the chlorophyll a/b content was double that of controls. Exogenous applications of zeatin to the PI-II-ipt leaves enhanced the level of resistance to the tobacco hornworm and almost completely inhibited normal development of the green peach aphid nymphs. Transcript levels of an acidic chitinase gene were low and minimally inducible in PI-II-ipt leaves. The mode of action of the cytokinin gene product on enhanced insect resistance is not clear but may involve the products of secondary metabolic pathways.

Expression of bacterial genes in transgenic tobacco: methods, applications and future prospects

“…The transfer of the Agrobacterium ipt gene, encoding cytokinin isopentenyl transferase, to transgenic plants has been shown to increase the levels of endogenous cytokinin and effectively enhance the resistance of plants to a number of insects. Smigocki et al (1993) introduced the ipt gene into tobacco plants by Agrobacterium-mediated transformation. The transgene was placed under the control of a woundinducible promoter from the potato proteinase inhibitor II (PI-IIK) gene.…”

Analysis of Interaction of Plant Genotype and Strain Agrobacterium Tumefaciens in Breeding of Potato Resistance to Colorado Potato Beetle

“…Осно вываясь на литературных данных [11], мы пред полагали, что у сортов с минимальной способнос тью к регенерации с помощью трансформации ге ном ipt удастся максимально повысить этот показатель. Кроме того, согласно литературным данным, формы с повышенным уровнем цитоки нинов обладают повышенной устойчивостью к биотическим и абиотическим факторам окружа ющей среды [12]. Поэтому в экспериментах по трансформации мы использовали штамм с геном ipt, с помощью которого в трансгенных растени ях можно повысить уровень цитокининов.…”

Prospects for using transgenic resistance to insects in crop improvement

“…Use of bacterial isopentenyl transferase (ipt) gene, involved in cytokinin biosynthesis, has been fused with a promoter from the proteinase inhibitor II (PI-IIK) gene and introduced into Nicotiana plumbaginifolia (Smigocki et al 1993). Manduca sexta larvae consumed up to 70% less of the PI-II-ipt leaf material on flowering plants than the larvae feeding on controls.…”