Phenotype Analysis of Tobacco Lines Expressing a Deregulated Arabidopsis Ca-ATPase (ACA2)

Functional foods go beyond simply supplying nutrients and are increasingly becoming a focus in the prevention and treatment of disease; however, the benefits of biofortified crops to human nutrition have not been well demonstrated. Modern breeding, molecular genetics, and biotechnology are currently focusing on how to improve the nutritional content in foods. Potatoes, carrots, and lettuce are popular vegetables eaten today and are targets in developing nutrient dense crops (biofortification). Biofortification of vegetables to increase calcium (Ca) in the diet has had promising results. Here we describe the current standing of nutrient biofortification of crops. Ca distribution within the plant cell moderates critical functions from signaling to growth and development and can affect overall plant vigor. The endoplasmic reticulum (ER) located Ca-ATPase ACA2 (Arabidopsis Ca-ATPase, isoform 2) is thought to play a role in intracellular calcium homeostasis. In yeast studies; a truncated pump (?80- ACA2) lacking the N-terminal region is about 10-fold more active than the full-length ACA2 pump. Single point mutations have been shown to increase activity of ACA2 in yeast as well. Previously in our lab, human feeding studies demonstrated that increased Ca accumulation and bioavailability in transgenic plants accompanied increased activity of the deregulated vacuolar Ca / H antiporter CAX1 (Cation Exchanger 1) termed sCAX1. In this study, transgenic tobacco plants expressing deregulated Ca transporters are compared. The phenotypes of deregulated vacuolar localized CAX and the ER localized ACA2 are compared. These results suggest deregulation of ACA2 may provide an additional tool to utilize in altering the calcium accumulation in agriculturally important crops.