Transcription termination factor required for processing and steady-state levels of plastid transcripts. Required for splicing of the chloroplastic Clp protease (ClpP) group IIa intron. Required for maturation of 16S rRNA and 23S rRNA in the chloroplast. Essential for embryogenesis (PubMed:21464319). Required for the maintenance of the correct levels of transcripts in the mitochondria and chloroplasts. Embryonic lethality when homozygous, due to growth arrest at the late globular stage. 'BELAYA SMERT' means white death in Russian. Belongs to the mTERF family. Truncated N-terminus. Sequencing errors.