Ethylene-induced opposite redistributions of calcium and auxin are essential components in the development of tomato petiolar epinastic curvature.
Calcium has been suggested as an important mediator of gravity signaling transduction within the root cap statocyte. In a horizontally-placed root, it is redistributed in the direction of the gravity vector (i.e. it moves downward) and its redistribution is closely correlated with auxin downward movement. However, the involvement of calcium in the regulation of ethylene-induced epinasty and auxin movement is not known. In this report, we examined the involvement of calcium in lateral auxin transport during ethylene-induced epinasty in an effort to understand the relationship among calcium, auxin, and ethylene. Ethylene-induced epinasty was further stimulated by exogenously applied Ca2+, the calcium effect being the strongest among divalent cations tested. Pretreatment with NPA, an auxin transport inhibitor, negated the promotive effect of calcium ions on the petiolar epinasty. Ethylene caused redistribution/differential accumulation of 45Ca2+ toward the morphologically lower (abaxial) side of the leaf petioles, an effect opposite to that of 14C-IAA redistribution. Verapamil, a Ca2+ channel blocker, inhibited ethylene-induced epinasty, as well as the redistribution of 14C-IAA and 45Ca2+. When the petiole was inverted in the presence or absence of ethylene, the direction of 45Ca2+ differential accumulation was still toward the morphologically abaxial side of the petiole during epinastic movement regardless of gravitational direction. These results suggest that gravity-insensitive, ethylene-induced Ca2+ redistribution and accumulation toward the abaxial side are closely coupled to the adaxial auxin redistribution/accumulation and, in turn, to the petiolar epinasty.
Lee
Yew
Y
Department of Life Science, Yonsei University, Wonju 220-710, Republic of Korea.
Jung
Jin-Woo
JW
Department of Life Science, Yonsei University, Wonju 220-710, Republic of Korea.
Kim
Seong-Ki
SK
Department of Life Science, Chung-Ang University, Seoul 156-756, Republic of Korea.
Hwang
Yong-Sic
YS
Department of Bioscience and Biotechnology, Konkuk University, Seoul 143-701, Republic of Korea.
Lee
June-Seung
JS
Department of Biological Science, Ewha Woman's University, Seoul 120-750, Republic of Korea.
Kim
Soo-Hwan
SH
Department of Life Science, Yonsei University, Wonju 220-710, Republic of Korea.
D000040:Abscisic Acid / Q000378:metabolism; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002122:Calcium Chloride / Q000378:metabolism / Q000494:pharmacology; D005030:Ethylenes / Q000494:pharmacology*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D018522:Gravitropism / Q000187:drug effects; D007210:Indoleacetic Acids / Q000378:metabolism* / Q000494:pharmacology; D018551:Solanum lycopersicum / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D008954:Models, Biological; D010937:Plant Growth Regulators / Q000494:pharmacology; D018515:Plant Leaves / Q000187:drug effects / Q000235:genetics / Q000378:metabolism
D005030:Ethylenes; D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D000040:Abscisic Acid; C036216:ethylene; D002122:Calcium Chloride; D002118:Calcium