Plant and Cell Physiology, 1994, Vol. 35, No. 8 1173-1177
© 1994
Epidermal Growth Factor Interacts with Indole-3-Acetic Acid and Promotes Coleoptile Growth
Department of Entomology and Institute of Ecology, University of Georgia Athens, Ga. 30602, U.S.A.
1Corresponding member.
We used coleoptile sections of Avena sativa, Sorghum bicolor, and Zea mays seedlings to examine interactions between epidermal growth factor (EGF) and indole-3-acetic acid (IAA) that may affect plant growth and development. Our 24-h bioassays employed three controls ranging in dilution from 104 to 108 g ml1: (1) 50 mM potassium-phosphate buffer solution (pH=6.0), (2) bovine serum albumin, a nonspecific protein; and (3) IAA; plus two treatments: (1) mouse epidermal growth factor (EGF) ranging from 106 to 1010gml1, and (2) EGF + IAA. In all three species growth in IAA, EGF, and EGF + IAA treatments showed significant increases over controls; EGF+IAA showed significant increases in growth over IAA alone. As the concentrations of IAA decreased, the EGF and IAA interaction became more pronounced. At the highest IAA concentrations, EGF + IAA increased growth rates ca. 2% to 39%, whereas at lower IAA concentrations EGF + IAA promoted growth as much as 121%, thereby lowering the normal IAA physiological set point up to three or four orders of magnitude. Our data suggest that an interaction between EGF and IAA may allow plants to recognize and respond to animal biochemical messengers, resulting in changes in plant cell elongation that ultimately may alter plant growth patterns.
(Received April 27, 1994; Accepted September 5, 1994)
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