2007 Annual Report 1a.Objectives (from AD-416) The objectives of this cooperative research project are to study the genetic elements that control carotenoid accumulation in plants and to develop food crops enriched with carotenoids. 1b.Approach (from AD-416) The approaches will include:. 1)to transform our recently cloned cauliflower Or gene into one of the cereal crops and to examine the effects of Or transgene on carotenoid accumulation and plant growth;. 2)to amplify the Or ortholog gene by PCR from a panel of maize and/or sorghum that captures the majority of the genetic variation in those species and transform the allelic variants into cell systems to find the best Or alleles for nutritional enhancement; and. 3)using molecular genetic, and genomic tools to identify and characterize novel genetic elements that regulate carotenoid accumulation based on diversity (association) analysis in maize and/or sorghum. 3.Progress Report This report documents research conducted under a specific cooperative agreement between ARS and Cornell University. Additional details of research can be found in the report for the in-house associated project 1907-21000-025-00D "Genomics approaches for improving nutritional quality of food crop species.” The main objectives of this project are to study the genetics elements that control carotenoid accumulation and to develop food crops enriched with carotenoid content. Specific activities during this period included to transform the recent cloned cauliflower Or gene into a staple crop and to examine the effects of the Or transgene on carotenoid accumulation. We have successfully generated transgenic potato lines expressing the cauliflower Or gene and showed that it can serve as a novel genetic tool to enhance carotenoid content to a level of 6-fold over the controls. We performed an in-depth molecular, biochemical and cytological characterization of these potato transgenic lines. We found that the Or gene can be used to facilitate the identification of the rate-limiting step of carotenoid biosynthetic pathway, which is very important for the metabolic engineering. Since cold storage is necessary to extend shelf life of many foods, we examined the effect of cold storage and observed that long-term cold storage dramatically enhances carotenoid accumulation in the Or transgenic tubers. Also we found that the Or gene mediates carotenoid accumulation in the transgenic tubers via inducing the formation of a metabolic sink to store the synthesized products. Research is in progress to introduce additional genes into the Or transgenic potato lines to see if manipulation of both biosynthetic capacity and sink strength can dramatically enhance carotenoid content in food crops. Research conducted under this agreement was monitored via regular meetings between the ADODR and Cornell cooperator.