AtYAF9A and AtYAF9B interact with AtSWC4 and the HSA-containing fragment of AtEAF1. (a) Coimmunoprecipitation test of interaction between AtYAF9A and AtYAF9B with the HSA-containing fragments of PIE1, AtEAF1 and AtINO80. Yaf9:nEYFP fusion proteins were detected with antibodies against GFP. Bands above the 55 kDa bars are nonspecific signals from immunoglobulin heavy chains. For additional experimental controls, see Additional file 5. (b) BiFC assay in Arabidopsis mesophyll protoplasts. Each co-transfection consisted of a pair of complementary BiFC constructs (nEYFP and cEYFP fusion, right panels, yellow dots indicate fluorescence complementation in the nuclei) and an ECFP construct as an internal transfection control (left panels, cyan). AtYAF9Bsv is the short splice variant of AtYAF9B, lacking the putative C-terminal SWC4-binding domain. (c) Enlarged images of single protoplasts showing nuclear localization of the EYFP fluorescence, indicating interaction between AtSWC4 and AtYAF9A (upper image) or AtYAF9B (lower image). Chloroplast autofluorescence is shown in red and ECFP fluorescence in cyan. Scale bar: 10 μm. Contrast and brightness were enhanced in all micrographs in (b) and (c) to improve clarity.