Our team goal is to generate heat tolerant tomato cultivars by understanding the molecular mechanisms that control tomato reproduction. Our central hypothesis is that pollen tubes are uniquely sensitive to heat stress, but that thermotolerant variants have been selected that facilitate reproductive success at high temperature. We will use genomics to define these molecular adaptations and determine whether they are sufficient to enhance fruit production of thermosensitive cultivars at high temperature.

Our preliminary studies found that multiple tomato cultivars that set fruit at high temperature also produce pollen tubes that grow at elevated temperatures that block growth in thermosensitive cultivars, including two of the most widely consumed varieties. Moreover, we found that the pistil modulates the heat stress response of the pollen tube. We also found that high temperature elevates reactive oxygen species in thermosensitive cultivars and that synthesis of flavonol antioxidants protects pollen at high temperatures.

We hypothesize that thermotolerant varieties express a pollen tube heat stress response that is either absent or diminished in thermosensitive cultivars and that the thermotolerant pistil buffers heat stress and facilitates pollen tube growth. Using reverse genetics, we will define the transcriptional changes that accompany heat stress in the pollen tube and the pistil, and also the functions of individual thermotolerance genes.