Abstract
KNOX genes play an important role in formation and maintenance of the shoot apical meristem (SAM), and its SAM-specific expression is essential for normal development of plants. We identified and analysed a rice mutant, onion, with ectopic KNOX expression. ONION encodes a fatty acid elongase and is expressed in an L1 layer of the SAM and young leaves. The onion mutant showed reduced expression of an L1 marker gene, abnormal wax formation in epidermis, reduced content of VLCFA and changes of expression of auxin-, SAM- and histone-related genes. These results suggest that ONION regulates shoot development by controlling fatty acid composition of an L1 layer and that a signal, which controls shoot development, might be transmitted from an L1 layer to inner cells. We also identified another gene which is expressed in a shoot apex and may play a role in fatty acid elongation.
