Interaction of a nodule specific, trans-acting factor with distinct DNA elements in the soybean leghaemoglobin Ibc(3) 5' upstream region.

Nuclear extracts from soybean nodules, leaves and roots were used to investigate protein-DNA interactions in the 5' upstream (promoter) region of the soybean leghaemoglobin lbc(3) gene. Two distinct regions were identified which strongly bind a nodule specific factor. A Bal31 deletion analysis delimited the DNA elements responsible for the binding of this factor, which map at nucleotides -223 to -246 (element 1) and -161 to -176 (element 2), relative to the start point of transcription. Competition experiments strongly suggest that both elements bind to the same nodule specific factor, but with different affinities. Elements 1 and 2 share a common motif, although their AT-rich DNA sequences differ. Element 2 is highly conserved at an analogous position in other soybean lb gene 5' upstream regions.