THE PLANT CELL, Vol 6, Issue 11 1543-1552, Copyright © 1994 by American Society of Plant Biologists
A Member of the Tomato Pto Gene Family Confers Sensitivity to Fenthion Resulting in Rapid Cell Death
G. B. Martin, A. Frary, T. Wu, S. Brommonschenkel, J. Chunwongse, E. D. Earle and S. D. Tanksley
Department of Agronomy, Purdue University, West Lafayette, Indiana 47907-1150
Leaves of tomato cultivars that contain the Pto bacterial resistance locus
develop small necrotic lesions within 24 hr after exposure to fenthion, an
organophosphorous insecticide. Recently, the Pto gene was isolated and
shown to be a putative serine/threonine protein kinase. Pto is one member
of a multigene family that is clustered within a 400-kb region on
chromosome 5. Here, we report that another member of this gene family,
termed Fen, is responsible for the sensitivity to fenthion. Fen was
isolated by map-based cloning using closely linked DNA markers to identify
a yeast artificial chromosome clone that spanned the Pto region. After
transformation with the Fen gene under control of the cauliflower mosaic
virus (CaMV) 35S promoter, tomato plants that are normally insensitive to
fenthion rapidly developed extensive necrotic lesions upon exposure to
fenthion. Two related insecticides, fensulfothion and fenitrothion, also
elicited necrotic lesions specifically on Fen-transformed plants.
Transgenic tomato plants harboring integrated copies of the Pto gene under
control of the CaMV 35S promoter displayed sensitivity to fenthion but to a
lesser extent than did wild-type fenthion-sensitive plants. The Fen protein
shares 80% identity (87% similarity) with Pto but does not confer
resistance to Pseudomonas syringae pv tomato. These results suggest that
Pto and Fen participate in the same signal transduction pathway.
