Overexpression of Malus xiaojinensis CS1 gene in tobacco affects plant development and increases iron stress tolerance

Iron is one of the essential micronutrients required by all plants and citric acid is considered to be the chelate substance in the long distance transport of iron. The expression of MxCS1 was enriched in active organs-leaf, root and phloem, which was strongly affected by Fe stress and IAA treatment, and weakly by ABA treatment in Malus xiaojinensis seedlings. This gene was introduced into the nongraminaceous plant tobacco, which promotes the synthesis of citrate synthase and increases the content of citric acid. Overexpression of MxCS1 improved Fe stress tolerance in transgenic tobacco and flowers firesented morphological abnormalities. Increased expression of MxCS1 in transgenic tobacco plants also resulted in early-flowering and increased concentrations of Fe, Mn, Cu, and Zn in young leaves and flowers. In addition to its role in long-distance metal transport, citric acid may be involved in the regulation of metal transfer within cells. These results suggest that citric acid excess influenced the functions of metal-requiring proteins, including some transcription factors. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.