Analysis of the tissue-specific expression pattern of WOX5 by promoter-reporter analysis in M. truncatula and pea. A, WOX5 expression in root tips of pea. B, WOX5 expression in root tips of M. truncatula. C and D, WOX5 expression at different stages of nodule development in pea at 5 dpi (C) and 21 dpi (D). E to I, WOX5 expression at different stages of nodule development in M. truncatula at 3 dpi (E and F), 5 dpi (G), 14 dpi (H), and 21 dpi (I). The inset in I shows an enlargement of the provascular strand. NP, Nodule primordium; VBI, vascular bundle initials; Xyl, xylem. Bars = 100 μm. J, Schematic representation of the WOX5 expression domain at different stages of nodule development. On average, for each stage, approximately 30 to 50 transgenic roots were analyzed with similar results. NI, Noninoculated M. truncatula root.