Elsbeth Walker ewalker at
Thu Jun 28 19:58:55 EST 2001

University of Massachusetts, Amherst

NSF-supported postdoctoral positions are available for a period of
three years to study the function of the eight members of the Yellow
Stripe-Like (YSL) family of Arabidopsis.  YSL family members were
identified based on their very strong sequence similarity to the YS1
protein of maize (Curie et al, 2001. Nature 409:346-349.).  The
function of maize YS1 is in the primary uptake of iron from the soil.
However, unlike other known plant iron transporters, YS1 transports
iron that is complexed by specific plant-derived Fe(III) chelators
called phytosiderophores.  There are eight YSL proteins encoded in
the Arabidopsis thaliana genome
(, but they cannot function
in phytosiderophore uptake, since Arabidopsis (like all non-grasses)
can neither synthesize nor use phytosiderophores.  Arabidopsis does
make and use a related compound, nicotianamine, which is the
biosynthetic precursor to phytosiderophores. Preliminary evidence
suggests that YSL proteins mediate transport of metals bound to
nicotianamine.  The many roles of nicotianamine in achieving proper
metal ion allocation in plants are incompletely understood, but there
is strong evidence that nicotianamine is necessary for distribution
of Fe, Zn, and Mn via phloem, and that it is required for transport
of Cu in xylem.  For the current project, the functions of the eight
Arabidopsis thaliana YSL genes will be determined from the narrowest
definition of function-biochemical function, to the broadest
definition of function-the role of these proteins in the growth and
development of the plant. By integrating this information for all
eight YSL genes, we will improve our understanding of metal ion
allocation mechanisms used by plants, and further the goal of
manipulating plant metal allocation for the purposes of
phytoremediation and improved value for human nutrition.

Please send a letter of application, CV, a set of reprints and
preprints, and names, addresses and email addresses of 3 references
to Elsbeth Walker, Biology  Dept., 611 North Pleasant St., University
of Massachussets, Amherst, MA 01003.  Ph: 413-545-0861;  fax: 413
545-3243;  e-mail: ewalker at

I will be available at the American Society of Plant Biologists
Meeting (July 21 to July 25, Providence, RI) to discuss possible
projects with interested candidates.

"The noble simplicity in the works of nature only too often
originates in the noble shortsightedness of the one who observes it."
-Geor Lichtenberg, 1784

Elsbeth L. Walker 		611 N. Pleasant St.
Assistant Professor		University of Mass, Amherst
Biology Department		Amherst, MA 01003
(413) 545-0861 voice		(413) 545-3243 fax



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