title: Rhizobium nod factors induce increases in intracellular free calcium and extracellular calcium influxes in bean root hairs
abstract: Application of Nod factors to growing, responsive root hairs of the bean Phaseolus vulgaris induces marked changes in both the intracellular cytosolic free calcium (Ca2+) and in the influx of extracellular [Ca2+]. The intracellular [Ca2+], which has been measured by ratiometric imaging in cells microinjected with fura-2-dextran (70 kDa), elevates within 5 min from approximately 400 nM to 1500 nM in localised zones in the root hair apex. Of particular note is the observation that the elevated regions of [Ca2+] appear to shift position during short time intervals. Increases in and fluctuations of the intracellular [Ca2+] are also observed in the perinuclear region after 10-15 min treatment with Nod factors. The extracellular Ca2+ flux, detected with the non-invasive, calcium specific vibrating electrode, is inwardly directed and also increases quickly in response to Nod factors from 13 pmol cm-2 s-1 to 28 pmol cm-2 s-1. Chitin-oligomers, which are structurally similar but biologically inactive when compared to the active Nod factors, fail to elicit changes in either intracellular or extracellular Ca2+. The similar timing and location of the intracellular elevations and the increased extracellular influx provide support for the idea that Ca2+ participates in secretion and cell wall remodelling, which occur in anticipation of root hair deformation and curling.
authors.initials: L
authors.lastname: Cardenas
authors.initials: JA
authors.lastname: Feijo
authors.initials: JG
authors.lastname: Kunkel
authors.initials: F
authors.lastname: Sanchez
authors.initials: T
authors.lastname: Holdaway-Clarke
authors.initials: PK
authors.lastname: Hepler
authors.initials: C
authors.lastname: Quinto