The goal of this project is to characterize the developmental, physiological, biochemical, and transcriptional mechanisms that underlie chilling tolerance in some grasses, and to use this information to improve the thermal tolerance of specific cereal crops. Cold temperatures in the US cause millions of dollars of damage to crops every year. This is particularly true for crops domesticated from tropical species, such as the grass cereals corn, sorghum, and millet. One reason that tropics-derived cereals fare best in warm environments is their special type of photosynthesis known as “C4". Photosynthesis is the process by which CO2 is converted into sugars, and it requires the diffusion of air through open pores, such that plants lose water when conditions are dry/hot. C4 cereals and their relatives have repeatedly evolved a trick whereby CO2 is concentrated in cells, allowing their pores to close and conserve water without greatly reducing photosynthetic sugar production. This strategy works well when temperatures are high, but it comes at the cost of poor tolerance to colder temperatures or "chilling tolerance". The aim of this project is to better understand how some C4 grasses have been able to circumvent the tradeoff between C4 photosynthesis and cold tolerance with an eye to designing C4 cereals that thrive under a range of temperatures. The first step is to determine the number of origins of chilling tolerance in the hundreds of C4 cereal grasses, and then to determine h