Elevation of the cytosolic free [Ca2+] is indispensable for the transduction of the Nod factor signal in alfalfa.
Plant Physiol
; 121(1): 273-80, 1999 Sep.
Article
em En
| MEDLINE
| ID: mdl-10482683
ABSTRACT
In root hairs of alfalfa (Medicago sativa), the requirement of Ca(2+) for Nod factor signaling has been investigated by means of ion-selective microelectrodes. Measured 50 to 100 microm behind the growing tip, 0.1 microM NodRm-IV(C162,S) increased the cytosolic free [Ca2+] by about 0.2 pCa, while the same concentration of chitotetraose, the nonactive glucosamine backbone, had no effect. We demonstrate that NodRm-IV(C162,S) still depolarized the plasma membrane at external Ca(2+) concentrations below cytosolic values if the free EGTA concentration remained low (=0.01 mM). Externally added Sr(2+) was able to replace Ca(2+), and to some extent even enhanced the Nod-factor-induced depolarization, whereas with Mg(2+) it was decreased. This suggests that the Nod factor response is triggered by Ca(2+) from external stores. The addition of the endomembrane Ca(2+)-ATPase inhibitor 2,5-di(t-butyl)-1, 4-benzohydroquinone, which presumably mobilizes Ca(2+) from Ins(1,4, 5)P(3)-sensitive stores, mimicked the Nod factor response, i.e. increased the cytosolic free [Ca2+], triggered Cl(-)-efflux, depolarized the plasma membrane, and alkalized the root hair space. In all cases a refractory state toward Nod factor perception was produced, indicating a shortcut of Nod factor signal transduction by releasing Ca(2+) from internal stores. These latter results strongly support the idea that an elevation of cytosolic free [Ca2+] is indispensable for the transduction of the Nod factor signal, which is consistent with the role of Ca(2+) as a second messenger.
Texto completo:
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Base de dados:
MEDLINE
Assunto principal:
Lipopolissacarídeos
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Cálcio
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Sinalização do Cálcio
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Medicago sativa
Idioma:
En
Ano de publicação:
1999
Tipo de documento:
Article