Ethylene plays multiple nonprimary roles in modulating the gravitropic response in tomato

• Published in: Plant physiology (Bethesda) 1999-07, Vol.120 (3), p.897-906
• Main Authors: Madlung, A, Behringer, F.J, Lomax, T.L
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Auxins; Biological and medical sciences; Curvature; duration; Economic plant physiology; ethylene; Ethylene production; Ethylenes - metabolism; Fundamental and applied biological sciences. Psychology; Gene expression regulation; Gravitropism; Gravitropism - genetics; Gravitropism - physiology; gravity; growth; Growth and Development; Hypocotyl - genetics; Hypocotyl - growth & development; Hypocotyl - metabolism; Hypocotyls; Indoleacetic Acids - metabolism; inhibition; Life Sciences (General); Lycopersicon esculentum; Lycopersicon esculentum - genetics; Lycopersicon esculentum - growth & development; Lycopersicon esculentum - metabolism; Movements; Mutants; Mutation; Phenotypes; Plant growth regulators; Plant Growth Regulators - metabolism; Plant Growth Regulators - physiology; Plant Physiological Phenomena; Plant physiology and development; Plants; red light; Seedlings; Solanum lycopersicum var. lycopersicum; Space life sciences; stems; Tomatoes; Tropism and nastic movements
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.120.3.897

Ethylene is known to interact with auxin in regulating stem growth, and yet evidence for the role of ethylene in tropic responses is contradictory. Our analysis of four mutants of tomato (Lycopersicon esculentum) altered in their response to gravity, auxin, and/or ethylene revealed concentration-dependent modulation of shoot gravitropism by ethylene. Ethylene inhibitors reduce wild-type gravicurvature, and extremely low (0.0005-0.001 microliter L(-1)) ethylene concentrations can restore the reduced gravitropic response of the auxin-resistant dgt (diageotropica) mutant to wild-type levels. Slightly higher concentrations of ethylene inhibit the gravitropic response of all but the ethylene-insensitive nr (never-ripe) mutant. The gravitropic responses of nr and the constitutive response mutant epi (epinastic) are slightly and significantly delayed, respectively, but otherwise normal. The reversal of shoot gravicurvature by red light in the lz-2(lazy-2) mutant is not affected by ethylene. Taken together, these data indicate that, although ethylene does not play a primary role in the gravitropic response of tomato, low levels of ethylene are necessary for a full gravitropic response, and moderate levels of the hormone specifically inhibit gravicurvature in a manner different from ethylene inhibition of overall growth.