Figure 4.

Selective control of host gene expression in the infected embryonic radicle. B–E and F–I were sectioned from single healthy and infected embryos, respectively, as illustrated in A. Sections were subjected to in situ hybridization with probes for PSbMV +ve RNA (B and F), polyubiquitin RNA (C and G), lox1:Ps:2 RNA (D and H) or PsHSP71.2 RNA (E and I). As observed in cotyledons, coordinate induction of polyubiquitin and HSP70 and down-regulation of lipoxygenase expression were observed. Note, to visualize the tissue structure in the absence of hybridization signal, these sections were photographed under joint-transmitted and epifluorescent light after staining the tissue sections with calcofluor.