SbRLK1, a receptor-like protein kinase of Sorghum bicolor (L.) Moench thatis expressed in mesophyll cells

To study the metabolic interactions between mesophyll and bundle-sheath cel ls of C-4 plants, protein kinases possibly involved in the regulatory proce sses and signal transduction pathways have been cloned and characterized. A receptor-like protein kinase (RLK) cDNA clone from the C-4 plant Sorghum b icolor (L.) Moench has been identified. The deduced protein was designated SbRLK1 for receptor-like protein kinase from S. bicolor. The putative cytop lasmic domain of SbRLK1 contains all amino acids that are characteristic of protein kinases. The extracellular domain contains five leucine-rich repea ts. The mRNA of the SbRLK1 gene accumulated to much higher levels in mesoph yll cells than in the bundle-sheath and was almost undetectable in roots. T his expression pattern indicates that SbRLK1 might be involved in the regul ation of specific processes in mesophyll cells.