Guard cells from leaf tissue of a transgenic tobacco expressing GFP-HFBI contain PBs. PBs in guard cells from cv. 81V9 transgenic plant expressing GFP-HFBI. A. GFP signal from PBs in guard cells and ER pattern in surrounding epidermal cells. B. Overlay of the GFP green channel with the transmission light channel confirming the localization of the PBs to the guard cells.