Isolation, Characterization and Transcriptome Analysis of a Cytokinin Receptor Mutant Osckt1 in Rice

Abstract

Cytokinins play important roles in regulating plant development, including shoot and root meristems, leaf longevity, and grain yield. However, the <i>in planta</i> functions of rice cytokinin receptors have not been genetically characterized yet. Here we isolated a rice mutant, <i>Osckt1</i>, with enhanced tolerance to cytokinin treatment. Further analysis showed that <i>Osckt1</i> was insensitive to aromatic cytokinins but responded normally to isoprenoid and phenylurea-type cytokinins. Map-based cloning revealed that the mutation occurred in a putative cytokinin receptor gene, histidine kinase 6 (<i>OsHK6</i>). <i>OsCKT1</i> was found to be expressed in various tissues throughout the plant and the protein was located in the endoplasmic reticulum. In addition, whole-genome gene expression profiling analysis showed that <i>OsCKT1</i> was involved in cytokinin regulation of a number of biological processes, including secondary metabolism, sucrose and starch metabolism, chlorophyll synthesis, and photosynthesis. Our results demonstrate that <i>OsCKT1</i> plays important roles in cytokinin perception and control of root development in rice.