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As an important agronomic trait in rice (<i>Oryza sativa</i>), moderate leaf rolling helps to maintain the erectness of leaves and minimize shadowing between leaves, leading to improved photosynthetic efficiency and grain yield. However, the molecular mechanisms underlying rice leaf rolling still need to be elucidated. Here, we isolated a rice mutant, <i>rl89</i>, showing adaxially rolled leaf phenotype due to decreased number and size of bulliform cells. We confirmed that the <i>rl89</i> phenotypes were caused by a single nucleotide substitution in <i>OsDRB2</i> (<i>LOC_Os10g33970</i>) gene encoding DOUBLE-STRANDED RNA-BINDING2. This gene was constitutively expressed, and its encoded protein was localized to both nucleus and cytoplasm. Yeast two-hybrid assay showed that OsDRB2 could interact with DICER-LIKE1 (DCL1) and OsDRB1-2 respectively. qRT-PCR analysis of 29 related genes suggested that defects of the <i>OsDRB2</i>-miR166-<i>OsHBs</i> pathway could play an important role in formation of the rolled leaf phenotype of <i>rl89</i>, in which <i>OsDRB2</i> mutation reduced miR166 accumulation, resulting in elevated expressions of the class III homeodomain-leucine zipper genes (such as <i>OsHB1</i>, <i>3</i> and <i>5</i>) involved in leaf polarity and/or morphology development. Moreover, <i>OsDRB2</i> mutation also reduced accumulation of miR160, miR319, miR390, and miR396, which could cause the abnormal leaf development in <i>rl89</i> by regulating expressions of their target genes related to leaf development.