“One critical surprise from the new research was the composition of the sensor. Rather than tracing it to a single source or protein, the researchers found that the sensor operates through two plant proteins working together. These were identified as 1) a “high leaf temperature1” protein kinase known as HT1 and 2) specific members of a mitogen-activated protein kinase family, or “MAP” kinase enzyme, known as MPK4 and MPK12.” Source and more reading.