Involved in leaf polarity establishment by functioning cooperatively with AS2 to repress abaxial genes ARF3, ARF4, KAN1, KAN2, YAB1 and YAB5, and the knox homeobox genes KNAT1, KNAT2, KNAT6, and STM to promote adaxial development in leaf primordia at shoot apical meristems at high temperatures. Involved in the processing of pre-rRNA intermediates at high temperatures. ATP + H2O = ADP + H(+) + phosphate Expressed in all tissues and organs examined including root, cotyledon, first and second leaves, third and fourth leaves, fifth and sixth leaves, shoot apex, flower, flower bud, cauline leaf and rosette leaves. The Q motif is unique to and characteristic of the DEAD box family of RNA helicases and controls ATP binding and hydrolysis. Plants are indistinguishable from that of wild-type at 16 degrees Celsius, however they generate a weak phenotype of pointed leaves at 22 degrees Celsius which become narrower at 26 degrees Celsius. In the leaves of plants grown at 26 degrees Celsius, the xylems are located on the adaxial sides and the phloems are on the abaxial sides, similar to those in the wild type. Plants with double mutations in this protein and in AS2 or AS1 protein have abaxialized filamentous and trumpet-like leaves with loss of the adaxial domain at high temperatures. In double mutants, shapes of epidermal cells of the filamentous leaves are simple and rectangular, similar to those of a petiole, but different from those of flat leaves of wild-type plants. The filamentous leaves of the double mutant at 26 degrees Celsius show primitive or no vascular tissue without apparent xylem cells inside the bundle sheath, suggesting defects in differentiation of xylem cells on the adaxial side. Belongs to the DEAD box helicase family. DDX47/RRP3 subfamily.