Tissue-specific expression of GbNRX1. A, qRT-PCR analysis of expression levels of GbNRX1 in cotton root, stem, cotyledon, true leaf, flower, ovule, fiber, and anther tissue. Error bars indicate sd from three technical replicates of one biological experiment. The experiments were repeated three times with similar results. B, Histochemical GUS staining of cotton plants transformed with the GbNRX1pro::GUS construct. (a) Young seedling; (b) true leaf without V. dahliae infection; (c) true leaf after V. dahliae infection for 48 h; (d) enlarged image of the section outlined by red dashed lines in (c); (e) root without V. dahliae infection; (f) root after V. dahliae infection for 48 h. C, Histochemical GUS staining of various organs from wild-type Arabidopsis plants transformed with GbNRX1pro::GUS. (a) Seedling; (b) true leaf; (c) vertical section of true leaf; (d) stem; (e) root; (f) cross section of root; (g) flower; (h) petals; (i) stigma stamen filaments; (j) seed pods. Arrows indicate vascular tissue. D, Immunofluorescence microscopy of GbNRX1 localized to the apoplast. GbNRX1 is mainly localized to the periphery of the cotton root cells without BFA treatment (a); aggregation of signals appears in BFA-treated cells (c); (b) and (d), enlarged images of the sections outlined in (a) and (c); localization of GbNRX1 in cotton root cells at 0, 0.5, 1, and 3 dpi, respectively (e–h). Bars = 50 µm.