Assistant Professor Auburn University Auburn, Alabama
Blueberry (Vaccinium corymbosum) is an economically important fruit crop that is native to North America. Fresh market production of blueberries in the U.S. has tripled since the 1970s, with a 10–20% increase annually since 2000. This popularity is remarkable given the blueberry’s relatively short domestication history (~100 years) and is attributed largely to consumer perception regarding the positive human health benefits of blueberries. A class of known pharmacologically important, yet under studied compounds in blueberries are iridoids. Iridoids are present in over 15 plant families and are potent natural products with a wide range of biological activities in humans including, anticancer, antibacterial and anti-inflammatory. Previous work has identified monotropein, an iridoid glycoside compound, in several wild Vaccinium species, but limited work has been done to identify this compound in cultivated North American blueberry species. To address this research limitation, we have analyzed over 80 berry and leaf samples from multiple species and commercial varieties of blueberry for monotropein production. The glycoside iridoid monotropein was successfully identified in only 5 of the 71 cultivars included in the panel, but all wild Vaccinium species. Currently, we are using a comparative genomics approach to identify key biosynthetic genes in the iridoid pathway to further elucidate the mechanism associated with the production of this natural product in blueberry. We are using genomic data from a known iridoid producing plant, Catharanthus roseus, and de novo transcriptome assembly from a monotropein-positive (M+) and monotropein-negative (M-) cultivar of blueberry to computational identify iridoid synthase (ISY), a key enzyme involved in formation of the iridoid scaffold. Using orthology analysis, we functionally characterized ISY from both the M+ and M- cultivars and found ISY from both the M+ and M- cultivars produced functional enzymes that catalyze the formation of iridoids. Additional work is being done to understand how transcript accumulation or expression of other genes in the biosynthetic pathway contribute to differential accumulation of the monotropein. Results from this study contribute new knowledge in our understanding of iridoid biosynthesis in blueberry and could lead to development of new cultivars with increased human health benefits.