NOD FACTOR-INDUCED EXPRESSION OF LEGHEMOGLOBIN TO STUDY THE MECHANISMOF NH4NO3 INHIBITION ON ROOT HAIR DEFORMATION

Nod factors secreted by Rhizobium leguminosarum by. viciae induce root hair deformation, the formation of nodule primordia, and the expressi on of early nodulin genes in Vicia sativa (vetch), Root hair deformati on is induced within 3 h in a small, susceptible zone (+/-2 mm) of the root, NH4NO3, known to be a potent blocker of nodule formation, inhib its root hair deformation, initial cortical cell divisions, and infect ion thread formation, To test whether NH4NO3 affects the formation of a component of the Nod factor perception-transduction system, we studi ed Nod factor-induced gene expression, The differential display techni que was used to search for marker genes, which are induced within 1 to 3 h after Nod factor application, Surprisingly, one of the isolated c DNA clones was identified as a leghemoglobin gene (VsLb1), which is in duced in vetch roots within 1 h after Nod factor application, By using the drug brefeldin A, it was then shown that VsLb1 activation does no t require root hair deformation, The pVsLb1 clone was used as a marker to show that in vetch plants grown in the presence of NH4NO(3), Nod f actor perception and transduction leading to gene expression are unaff ected.