Required for the formation of pollen surface apertures, which arise by restriction of exine deposition at specific sites. The aperture length depends on the INP1 dosage (PubMed:23136373). Does not play a role in specifying the number or position of apertures (PubMed:27177036). Acts in a sporophytic manner (PubMed:23136373). Located at 3 equidistant spots close to the pollen equator. 3-D reconstruction demonstrates that INP1 is restricted not to just 3 spots, but to 3 long and narrow regions underlying the position of future apertures. Expressed only in anthers and in pollen. Not detected in other flower tissues, stems, leaves and siliques. Detected in stage 9 buds and appears to be confined to microspores. Normal and fertile plants with pollen having normal reticulate exine patterning but completely lacking apertures. The number and position of apertures is strongly correlated with pollen ploidy. Extended C-terminus.