|Xu, Qiang -|
|Owsiany, Katherine -|
|Welsch, Ralf -|
|Chitchumroonchokchai, Chureeporn -|
|Lu, Shan -|
|Van Eck, Joyce -|
|Deng, Xiuxin -|
|Failla, Mark -|
Submitted to: Molecular Plant
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 30, 2012
Publication Date: March 1, 2012
Citation: Li, L., Yang, Y., Xu, Q., Owsiany, K., Welsch, R., Chitchumroonchokchai, C., Lu, S., Van Eck, J., Deng, X., Failla, M., Thannhauser, T.W. 2012. The Or gene enhances carotenoid accumulation and stability during post-harvest storage of potato tubers. Molecular Plant. 5:339-352. Interpretive Summary: Vitamin A deficiency is one of the most prevalent nutrient deficiencies in many parts of the world. Provitamin A carotenoids in staple crops are not very stable during storage and their loss compromises nutritional quality. Excitedly, we found that the Or gene not only promotes retention of provitamin A level, but also continuously stimulates its accumulation in the Or potato tubers during long-term storage. The increased carotenoid accumulation was found to be associated with the formation of lipoprotein-carotenoid sequestering substructures in chromoplasts, as well as with the enhanced abundance of a key enzyme in the carotenoid biosynthetic pathway. Furthermore, the provitamin A carotenoids stored in chromoplasts are bioavailable. Proteomic analysis identifies three major functional groups of proteins that likely impact carotenoid accumulation. Our results show that regulation of carotenoid sequestration capacity is an important mechanism by which carotenoid stability is regulated. Thus, induction of chromoplast formation offers a potential to develop staple crops with a unique capacity to synthesize and stabilize carotenoids during plant growth and post-harvest storage.
Technical Abstract: Provitamin A carotenoids in staple crops are not very stable during storage and their loss compromises nutritional quality. To elucidate the fundamental mechanisms underlying carotenoid accumulation and stability, we investigated transgenic potato tubers that express the cauliflower Orange (Or) gene. We found that the Or transgene not only promoted retention of beta-carotene level, but also continuously stimulated its accumulation during five months of cold storage. In contrast, no increased levels of carotenoids were observed in the tubers of vector-only controls or a yellow-flesh variety during the same period of storage. The increased carotenoid accumulation was found to be associated with the formation of lipoprotein-carotenoid sequestering structures, as well as with the enhanced abundance of phytoene synthase, a key enzyme in the carotenoid biosynthetic pathway. Furthermore, the provitamin A carotenoids stored were shown to be stable during simulated digestion and accessible for uptake by human intestinal absorptive cells. Proteomic analysis identified three major functional groups of proteins (i.e., heat shock proteins, glutathione-S-transferases, and carbohydrate metabolic proteins) that are potentially important in the Or-regulated carotenoid accumulation. Our results show that regulation of carotenoid sequestration capacity is an important mechanism by which carotenoid stability is regulated. Our findings suggest that induction of a proper sink structure formation in staple crops may provide the crops with unique ability to promote and/or stabilize provitamin A accumulation during plant growth and post-harvest storage.