Plant Molecular Biology

, Volume 23, Issue 2, pp 325–335

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

  • A. Smigocki
  • J. W. NealJr.
  • I. McCanna
  • L. Douglass
Research Articles

DOI: 10.1007/BF00029008

Cite this article as:
Smigocki, A., Neal, J.W., McCanna, I. et al. Plant Mol Biol (1993) 23: 325. doi:10.1007/BF00029008

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.

Key words

cytokininzeatinNicotianaManduca sextaMyzus persicae

Copyright information

© Kluwer Academic Publishers 1993

Authors and Affiliations

  • A. Smigocki
    • 1
  • J. W. NealJr.
    • 2
  • I. McCanna
    • 1
  • L. Douglass
    • 3
  1. 1.Plant Molecular Biology Laboratory Agricultural Research ServiceU.S. Department of AgricultureBeltsvilleUSA
  2. 2.Florist and Nursery Crops Laboratory, Agricultural Research ServiceU.S. Department of AgricultureBeltsvilleUSA
  3. 3.Animal Sciences DepartmentUniversity of MarylandCollege ParkUSA