AUTHOR=Bauer Petra , Schuler Mara 

TITLE=Heavy Metals Need Assistance: The Contribution of Nicotianamine to Metal Circulation Throughout the Plant and the Arabidopsis NAS Gene Family

JOURNAL=Frontiers in Plant Science

VOLUME=2

YEAR=2011

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2011.00069

DOI=10.3389/fpls.2011.00069

ISSN=1664-462X

ABSTRACT=<p>Understanding the regulated inter- and intra-cellular metal circulation is one of the challenges in the field of metal homeostasis. Inside organisms metal ions are bound to organic ligands to prevent their uncontrolled reactivity and to increase their solubility. Nicotianamine (NA) is one of the important ligands. This non-proteinogenic amino acid is synthesized by nicotianamine synthase (NAS). NA is involved in mobilization, uptake, transport, storage, and detoxification of metals. Much of the progress in understanding NA function has been achieved by studying mutants with altered nicotianamine levels. Mild and strong <italic>Arabidopsis</italic> mutants impaired in nicotianamine synthesis have been identified and characterized, namely <italic>nas4x-1</italic> and <italic>nas4x-2</italic>. <italic>Arabidopsis thaliana</italic> has four <italic>NAS</italic> genes. In this review, we summarize the structure and evolution of the <italic>NAS</italic> genes in the <italic>Arabidopsis</italic> genome. We summarize previous results and present novel evidence that the four <italic>NAS</italic> genes have partially overlapping functions when plants are exposed to Fe deficiency and nickel supply. We compare the phenotypes of <italic>nas4x-1</italic> and <italic>nas4x-2</italic> and summarize the functions of <italic>NAS</italic> genes and NA as deduced from the studies of mutant phenotypes.</p>