Required for regulated cell division and differentiation in meristems and embryos, thus modulating adaxial-abaxial polarity. Regulates the progression of cell cycle and DNA replication (e.g. G2/M progression and intrachromosomal recombination) and the expression of genes during development, especially genes nearby the Helitron transposons. Mostly expressed in flower buds and flowers, and, to a lower extent, in leaves, stems, seedlings, roots and siliques. Morphological defects including short roots, abnormal phyllotaxy with defects in adaxial-abaxial polarity of leaves, highly serrated and asymmetric leaves, and fasciation, as well as defective patterns of cell division and differentiation in meristems and during embryogenesis. Constitutively activated DNA damage responses associated with a defect in G2/M cell cycle progression, but no activation of transcriptionally silenced genes. Hypersensitive to DNA-damaging agents such as the DNA cross-linking agent mitomycin C (MMC) and the DNA-alkylating agent methyl-methane sulfonate (MMS). Reduced frequency of intrachromosomal homologous recombination. 'Tebichi' means the 'cloven hoof of a pig' in the regional dialect of the southernmost area of Japan. Belongs to the helicase family.