Component of minor spliceosome required for U12-type intron splicing and alternative splicing of many introns. Binds specifically to U12 snRNA, which is necessary for branch-point site recognition. Required for normal plant development. Component of the U11/U12 snRNPs that are part of the U12-type spliceosome. Forms a complex with U12 snRNA. Ubiquitous. Lethal when homozygous.