Plant-specific TFIIB-related protein that plays important roles in pollen germination and embryogenesis, possibly by regulating gene expression through interaction with TBP2 and the subunits of RNA polymerases. Binds double-stranded DNA in vitro. Can form homodimer (PubMed:23713077). Interacts with TBP2 (PubMed:23713077). Expressed in shoot apical meristems, root tips, primordia of lateral roots, inflorescences, developing pollen grains and embryos. In developing pollen grains, expressed in the vegetative nuclei at the early binucleate stage and during the second pollen mitosis. Expression significantly decreases at the late trinucleate developmental stage. Not expressed in released mature pollen grains, germinating pollen grains and pollen tubes. Embryonic lethality and aborted seed when homozygous.