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Rapid alkalinization in alfalfa root hairs in response to rhizobial lipochitooligosaccharide signals
Author(s) -
Felle Hubert H.,
Kondorosi Éva,
Kondorosi Adám,
Schultze Michael
Publication year - 1996
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.1996.10020295.x
Subject(s) - nod , nod factor , root hair , biology , microbiology and biotechnology , sulfation , intracellular , biochemistry , depolarization , chemistry , biophysics , bacteria , symbiosis , root nodule , genetics , gene
Rhizobial lipochitooligosaccharides (Nod factors) function as symbiotic signals that trigger root hair deformations and cortical cell divisions on the roots of leguminous plants in a host‐specific manner. By using pH‐sensitive microelectrodes, it is shown that alfalfa root hair cells respond to Rhizobium meliloti Nod factors with a rapid intracellular alkalinization of 0.2–0.3 pH units. This alkalinization remained as long as the Nod factor was present, but slowly reversed after removal of the signal. The response was most sensitive to the sulfated tetrameric Nod factor, NodRm‐IV(C16:2,S), which is morphogenic on the host plant alfalfa, suggesting a role in a signal transduction cascade. Non‐sulfated Nod factor as well as chitooligosaccharides elicited a pH c change only at elevated concentrations. The increase of PH c in response to sulfated Nod factor was concomitant with a depolarization of the plasma membrane potential whereas the PH c change in response to non‐sulfated Nod factor occurred in the absence of membrane depolarization. In addition, whereas a first dose of sulfated Nod factor inhibited the subsequent response to a second dose of the same molecule, it did not significantly repress the activity of non‐sulfated Nod factor. These results indicate that sulfated and non‐sulfated Nod factors act independently and suggest the existence of two Nod signal perception systems, one transmitting the host‐specific signal, the other representing an ancient reception system for a generic Nod factor structure.