Plant, Cell and Environment 26: 661-671 (2003)
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Calcium requirement for ethylene-dependent responses involving 1-aminocyclopropane-1-carboxylic
acid oxidase in radicle tissues of germinated pea seeds
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Luciana Petruzzelli (1), Monica Sturaro (1), Davide Mainieri (1),
Gerhard Leubner-Metzger (2)
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(1) Istituto Biosintesi Vegetali, C.N.R., via Bassini 15, I-20133 Milano,
Italy
(2) Institut für Biologie II, Botanik, Albert-Ludwigs-Universität,
Schänzlestr. 1, D-79104 Freiburg i. Br., Germany
Received: 12 July 2002 / Accepted: 30 October 2002
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Abstract. The Ca2+ requirements of ethylene-dependent responses
were investigated in germinating seeds of Pisum sativum L. using
1-aminocyclopropane-1-carboxylic acid (ACC) oxidase (Ps-ACO1), ACC synthase
(Ps-ACS2) and class I ß-1,3-glucanase as molecular markers. Ethylene
biosynthesis and responsiveness are localized to the elongation and differentiation
zones of the pea radicle. Ethylene treatment induced ectopic root hair formation
in the cell elongation zone and promoted root hair elongation growth in
the radicles of germinated seeds. Characterized Ca2+ antagonists, including
EGTA, lanthanum, verapamil, ruthenium red, W-7, lithium and neomycin, were
used to test for the involvement of the apoplastic and the intracellular
Ca2+-pool, the Ca2+/calmodulin complex and the phoshoinositide (PI) cycle
in the ethylene responses. Ca2+ release from internal pools, but not appreciably
apoplastic Ca2+, is involved in the transcriptional induction by ethylene
of Ps-ACO1 and in ectopic root hair formation in the radicle elongation
zone of germinated pea seeds. Furthermore, the Ca2+/calmodulin complex and
the PI cycle seem to be involved in these ethylene responses. In contrast,
both the intracellular and the apoplastic Ca2+-pools are required for the
negative and positive ethylene-responses on the gene expression of PS-ACS2
and class I ß-1,3-glucanase, respectively; and, apoplastic Ca2+ also
promotes root hair elongation growth. Tissues from adult plants and germinating
seeds exhibit temporal and spatial differences in the signal/response coupling
by Ca2+ of ethylene-regulated processes.
Key words: 1-Aminocyclopropane-1-carboxylic acid oxidase - Calcium
signaling - Ethylene signaling - Embryonic root - Pisum - Root hair development
Links to other publications on ethylene and pea seed germination:
Petruzzelli et al. 2000
Petruzzelli et al. 1999
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