TY - JOUR
T1 - Arabidopsis NPCC6/NaKR1 is a phloem mobile metal binding protein necessary for phloem function and root meristem maintenance
AU - Tian, Hui
AU - Baxter, Ivan R.
AU - Lahner, Brett
AU - Reinders, Anke
AU - Salt, David E.
AU - Ward, John M.
PY - 2010/12
Y1 - 2010/12
N2 - SODIUM POTASSIUM ROOT DEFECTIVE1 (NaKR1; previously called NPCC6) encodes a soluble metal binding protein that is specifically expressed in companion cells of the phloem. The nakr1-1 mutant phenotype includes high Na+, K+, Rb+, and starch accumulation in leaves, short roots, late flowering, and decreased long-distance transport of sucrose. Using traditional and DNA microarray-based deletion mapping, a 7-bp deletion was found in an exon of NaKR1 that introduced a premature stop codon. The mutant phenotypes were complemented by transformation with the native gene or NaKR1-GFP (green fluorescent protein) and NaKR1-β-glucuronidase fusions driven by the native promoter. NAKR1-GFP was mobile in the phloem; it moved from companion cells into sieve elements and into a previously undiscovered symplasmic domain in the root meristem. Grafting experiments revealed that the high Na+ accumulation was due mainly to loss of NaKR1 function in the leaves. This supports a role for the phloem in recirculating Na+ to the roots to limit Na+ accumulation in leaves. The onset of root phenotypes coincided with NaKR1 expression after germination. The nakr1-1 short root phenotype was due primarily to a decreased cell division rate in the root meristem, indicating a role in root meristem maintenance for NaKR1 expression in the phloem.
AB - SODIUM POTASSIUM ROOT DEFECTIVE1 (NaKR1; previously called NPCC6) encodes a soluble metal binding protein that is specifically expressed in companion cells of the phloem. The nakr1-1 mutant phenotype includes high Na+, K+, Rb+, and starch accumulation in leaves, short roots, late flowering, and decreased long-distance transport of sucrose. Using traditional and DNA microarray-based deletion mapping, a 7-bp deletion was found in an exon of NaKR1 that introduced a premature stop codon. The mutant phenotypes were complemented by transformation with the native gene or NaKR1-GFP (green fluorescent protein) and NaKR1-β-glucuronidase fusions driven by the native promoter. NAKR1-GFP was mobile in the phloem; it moved from companion cells into sieve elements and into a previously undiscovered symplasmic domain in the root meristem. Grafting experiments revealed that the high Na+ accumulation was due mainly to loss of NaKR1 function in the leaves. This supports a role for the phloem in recirculating Na+ to the roots to limit Na+ accumulation in leaves. The onset of root phenotypes coincided with NaKR1 expression after germination. The nakr1-1 short root phenotype was due primarily to a decreased cell division rate in the root meristem, indicating a role in root meristem maintenance for NaKR1 expression in the phloem.
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U2 - 10.1105/tpc.110.080010
DO - 10.1105/tpc.110.080010
M3 - Article
C2 - 21193571
AN - SCOPUS:79551639531
SN - 1040-4651
VL - 22
SP - 3963
EP - 3979
JO - Plant Cell
JF - Plant Cell
IS - 12
ER -