SR-like splicing factor required for phytochrome B (phyB) signal transduction and involved in phyB-dependent alternative splicing. Expressed in leaves, inflorescence stems, roots, flower buds, open flowers and siliques. The RS domain (871-946) is required for phytochrome B signal transduction through alternative splicing regulation. Dwarfism and sterile flowers when homozygous and semi-sterility when heterozygous under normal growth conditions. Reduced inhibition of hypocotyl elongation under continuous red light.