Overexpression of OsZHD1, a zinc finger homeodomain class homeobox transcription factor, induces abaxially curled and drooping leaf in rice

Leaf rolling is receiving considerable attention as an important agronomic trait in rice (Oryza sativa L.). However, little has been known on the molecular mechanism of rice leaf rolling, especially the abaxial rolling. We identified a novel abaxially curled and drooping leaf-dominant mutant from a T₁ transgenic rice line. The abaxially curled leaf phenotypes, co-segregating with the inserted transferred DNA, were caused by overexpression of a zinc finger homeodomain class homeobox transcription factor (OsZHD1). OsZHD1 exhibited a constitutive expression pattern in wild-type plants and accumulated in the developing leaves and panicles. Artificial overexpression of OsZHD1 or its closest homolog OsZHD2 induced the abaxial leaf curling. Histological analysis indicated that both the increased number and the abnormal arrangement of bulliform cells in leaf were responsible for the abaxially curled leaves. We herein reported OsZHD1 with key roles in rice morphogenesis, especially in the modulating of leaf rolling, which provided a novel insight into the molecular mechanism of leaf development in rice.