University of New Hampshire
Mentor: Dr. Subhash Minocha, Department of Biological Sciences
Metabolic Engineering of Spermidine Synthase in Rice for Holistic Study of Drought and Salt Tolerance
Abiotic stresses are important constraints on crop productivity. Paddy-grown rice is particularly susceptible to drought and salt stress, which have negative effects on carbon and nitrogen intake thus limiting plant growth and grain yield. Polyamines (PAs), mainly putrescine, spermidine, and spermine, are important molecules in plant metabolism and have been implicated in abiotic stress responses, both as protectors of plants from stress and preparing the plant for tolerance of stress. This has led to genetic manipulation of PA metabolism aimed at improving drought and salt tolerance in rice and several other crops. Prior to overexpressing PA biosynthetic genes in order to produce a multiple-stress-tolerant plant, we have profiled the response of a commercial rice variety to drought and salt stress in terms of changes in growth and PA content. We found that PAs may be involved in recovery from stress, but levels during stress appear to fluctuate widely. To minimize sampling errors, we also studied differences in PA contents among different parts of the long, morphologically heterogeneous rice leaf. The PA levels were significantly higher in the leaf blade than the sheath, which may have affected our abiotic stress results. Together, the results will help us plan future strategies of transgenic rice plants with modified PA metabolism, which will ultimately increase scientific understanding of abiotic stress tolerance for plant improvement.