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

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Abstract
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 lbc3 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.