The ontogenetic control of leaf epinasty during abiotic stress in tomato

Plants suffer from all kinds of biotic and abiotic stress conditions, which are often regulated by the plant hormone ethylene. One of the most enigmatic abiotic stress responses is epinasty, which is the downwards bending of the leaves. Leaf epinasty is observed in many important crops including tomato, and is often the result of root hypoxia and/or salinity stress. Our preliminary results have showed that epinasty is developmentally regulated, meaning that old leaves are sensitive to stress while young leaves are not. This ontogenetic aspect is linked to a shift in the ethylene metabolism of the different leaves. Besides the involvement of ethylene, little is known about the exact molecular regulation of epinasty as well as the physiological significance of this response. Therefore, we will profoundly characterize the physiological state of the entire plant during abiotic stress. We will furthermore investigate the tissue specific changes that occur in the adaxial and abaxial side of the petiole during epinasty using histology and transcriptomics. Additionally we will look for new regulators of epinasty by performing a genetic screen for stress-induced epinasty using tomato EMS mutants. The biological significance of these new regulators will also be further studied. Altogether, our project aims to finally answer unresolved questions regarding the mystery of leaf epinasty and link it with the ontogeny of ethylene in tomato plant suffering from abiotic stress.