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Perception of Bradyrhizobium japonicum Nod factor by soybean [Glycine max (L.) Merr.] root hairs under abiotic stress conditions.Duzan HM, Zhou X, Souleimanov A, Smith DL Department of Plant Science, McGill University, Macdonald Campus, 21111 Lakeshore Road, Ste. Anne de Bellevue, Quebec, Canada H9X 3V9. Suboptimal growth conditions, such as low rhizosphere temperature, high salinity, and low pH can negatively affect the rhizobia-legume symbioses, resulting in poor nodulation and lower amounts of nitrogen fixed. Early stages of the Bradyrhizobium japonicum-soybean [Glycine max (L.) Merr.] symbiosis, such as excretion of genistein (the plant-to-bacteria signal) and infection initiation can be inhibited by abiotic stresses; however, the effect on early events modulated by Nod factors (bacteria-to-plant signalling), particularly root hair deformations is unknown. Thus, the objective of this study was to evaluate the perception of Nod factor by soybean root hairs under three stress conditions: low temperature, low pH, and high salinity. Three experiments were conducted using a 1:1 ratio of Nod Bj-V (C(18:1), MeFuc) and Nod Bj-V (Ac, C(16:0), MeFuc). Nod factor induced four types of root hair deformation (HAD), wiggling, bulging, curling, and branching. Under optimal experimental conditions root hair response to the three levels of Nod factor tested (10(-6), 10(-8), and 10(-10) M) was dose-dependent. The highest frequency of root hair deformations was elicited by the 10(-6) M level. Root hair deformation decreased with temperature (25, 17, and 15 degrees C), low pH, and high salinity. Nod factor concentration did not interact with either low temperature or pH. However, salinity strongly inhibited HAD responses to increases in Nod factor concentration. Thus, the addition of higher levels of Nod factor is able to overcome the effects of low pH and temperature stress, but not salinity. Published 15 November 2004 in J Exp Bot, 55(408): 2641-6.
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