ARS | Publication request: Expression of an "Arabidopsis CAX2" variant in potato tubers increases calcium levels with no accumulation of manganese

Submitted to: Plant Cell Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 1, 2006
Publication Date: October 6, 2006
Citation: Kim, C.K., Han, J-S., Lee, H-S., Oh, J-Y., Shigaki, T., Park, S.H., Hirschi, K. 2006. Expression of an "Arabidopsis CAX2" variant in potato tubers increases calcium levels with no accumulation of manganese. Plant Cell Reports. 25(11):1226-1232.

Interpretive Summary: Potatoes are an important agricultural commodity and are widely consumed worldwide. The goal of this study was to increase calcium levels in potatoes through expression of plant calcium transporters which can mine the calcium out of the soil. In this report we have documented that our engineered potatoes contain more calcium and do not contain higher levels of any potentially toxic metals. In the future, these new potatoes could be an important source of calcium for human consumption.

Technical Abstract: Previously, we made a chimeric "Arabidopsis thaliana" vacuolar transporter CAX2B [a variant of N-terminus truncated form of CAX2 (sCAX2) containing the "B" domain from CAX1] that has enhanced calcium (Ca[2+]) substrate specificity and lost the manganese (Mn[2+]) transport capability of sCAX2. Here, we demonstrate that potato ("Solanum tuberosum" L.) tubers expressing the CAX2B contain 50–65% more calcium (Ca[2+]) than wild-type tubers. Moreover, expression of "CAX2B" in potatoes did not show any significant increase of the four metals tested, particularly manganese (Mn[2+]). The "CAX2B"-expressing potatoes have normally undergone the tuber/plant/tuber cycle for three generations; the trait appeared stable through the successive generations and showed no deleterious alternations on plant growth and development. These results demonstrate the enhanced substrate specificity of CAX2B in potato. Therefore, CAX2B can be a valuable tool for Ca[2+] nutrient enrichment of potatoes with reduced accumulation of undesirable metals.