Associate Professor The College of New Jersey Ewing, New Jersey
Body of Abstract: Plants regularly experience mild stresses for which they are equipped to adjust gene expression and biochemistry to maintain growth and reproduction. Metabolic tradeoffs between growth and defense allow plants to optimize resource use in response to adverse environmental conditions. Little is known about the subtle changes in secondary metabolites and growth promoting hormones during stress acclimation. Many cytochrome P450 enzymes (CYPs) are induced by environmental stresses to facilitate shifts in metabolism. Plant genome sequencing has revealed the presence of thousands of CYP genes with an average of about 300 genes per plant. The CYP72A subfamily appears to have members in all angiosperms and provides the potential for diverse biochemical functions in each plant species in response to external stresses. CYP72A9 from Arabidopsis is expressed in immature seeds and inactivates gibberellins as part of the dormancy process, and its GA hydroxylase activity appears to be conserved in a few CYP72As across the plant kingdom. The gene encoding CYP72A9 is induced by various abiotic stresses, such as heat and osmotic stress. Our work tests the hypothesis that CYP72A9 modulates plant growth in response to environmental stress. We measured plant growth at various stages of development when CYP72A9 mutant and wild type plants are exposed to abiotic stresses individually or in combination. Plants deficient in CYP72A9 are larger than wild type plants when exposed to individual and a combinations of abiotic stresses. These results suggest that under a variety of adverse environmental conditions, young plants are slowing growth through GA inactivation. There is little support for a response later in plant development. Unraveling the stress-induced regulation of gibberellin homeostasis contributes to our understanding of the growth-defense tradeoffs in plant acclimation to adverse conditions.