Mutations in the rice liguleless gene result in a complete loss of the auricle, ligule, and laminar joint
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The area between the upper part of the leaf sheath and the basal portion of the leaf blade contains several specialized organs, such as the laminar joint, auricle and ligule. Here we report the identification of T-DNA insertional mutant lines that lack all of these organs. The gene knocked out in the mutant lines encodes a protein that contains a SBP (SQUAMOSA promoter Binding Protein)-domain and is highly homologous to the maize LIGULELESS1 (LG1) gene. At the amino acid sequence level, the OsLG1 protein is 69% identical to maize LG1 and 78% identical to barley LG1. We named the rice gene OsLIGULELESS1 (OsLG1). Transient expression of an OsLG1:RFP (Red Fluorescent Protein) fusion protein indicated that the protein is localized to the nucleus. Transgenic plants harboring the OsLG1 promoter:GUS (β-glucuronidase) reporter gene construct display preferential expression in developing laminar joint regions and meristemic regions. The gene is also weakly expressed in the ligule, auricles, and leaf sheaths at the basal region. These results indicate that OsLG1 is a transcriptional factor that plays an important role in building the laminar joint between leaf blade and leaf sheath boundary, thereby controlling ligule and auricle development.
KeywordsLaminar joint Liguleless Rice SBP T-DNA insertion mutant
We thank Jong-seong Jeon, Sichul Lee, Shinyoung Lee, Sunok Moon, Choong-Hwan Ryu, and Dong-Yean Lee for helpful discussion, Young-Ock Kim and Ja Kyung Yi for assistance in protoplast cell culturing, Min-Jung Han for technical instruction the real-time PCR analysis, In-soon Park for generating transgenic GUS plants. We also express our thanks to Chahm An for critical reading of the manuscript. This work was funded in part by grants from the Crop Functional Genomic Center, the 21st Century Frontier Program (CG-1111); from the Biogreen 21 Program, Rural Development Administration; and from the Korea Science and Engineering Foundation (KOSEF) through the National Research Laboratory Program funded by the Ministry of Science and Technology (M10600000270–06J0000–27010).
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