Two NB markers and splicing components were present in NBs (designated type II), revealing the dynamics of FIT to accumulate in NBs. Confocal images showing localization of FIT-GFP and NB markers (type II) upon coexpression in the nucleus at t = 0 and t = 5 min. (A and B) Coexpression of FIT-GFP with A, SR45-mRFP, and B, SRm102-mRFP. Type II NB markers localized inside NBs at t = 0 and t = 5 min. Similar localization patterns were observed upon single expression, showing that SR45 and SRm102 are present in distinct NB types (compare with Fig. S3, C and D). FIT-GFP colocalized with type II markers in their distinct NBs at t = 5 min, but not t = 0. FIT-GFP additionally localized in FIT NBs at t = 5 min. Type II markers were not present in FIT NBs, while FIT-GFP became recruited into the distinct type II NBs upon the light trigger. Hence, FIT NBs could be associated with speckle components. Scale bar: 2 µm. Filled arrowheads indicate colocalization in NBs, empty arrowheads indicate no colocalization in NBs. G = GFP; R = mRFP. Fluorescence protein analysis was conducted in transiently transformed N. benthamiana leaf epidermis cells, following the standardized FIT NB analysis procedure. In all examined cells, the proteins showed partial colocalization. Representative images from two to five independent experiments are shown. For data with type I markers (no colocalization) and type III markers (full colocalization) see Fig. S3, A and B; and Fig. 6.