Publication Information
Lan et al., 2012
No external accession available
Abstract
Plant Physiol. 2012 May;159(1):403-17. doi: 10.1104/pp.112.193987. Epub 2012 Mar
21.
Quantitative phosphoproteome profiling of iron-deficient Arabidopsis roots.
Lan P(1), Li W, Wen TN, Schmidt W.
Author information:
(1)Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529,
Taiwan.
Iron (Fe) is an essential mineral nutrient for plants, but often it is not
available in sufficient quantities to sustain optimal growth. To gain insights
into adaptive processes to low Fe availability at the posttranslational level,
we conducted a quantitative analysis of Fe deficiency-induced changes in the
phosphoproteome profile of Arabidopsis (Arabidopsis thaliana) roots. Isobaric
tags for relative and absolute quantitation-labeled phosphopeptides were
analyzed by liquid chromatography-tandem mass spectrometry on an LTQ-Orbitrap
with collision-induced dissociation and high-energy collision dissociation
capabilities. Using a combination of titanium dioxide and immobilized metal
affinity chromatography to enrich phosphopeptides, we extracted 849 uniquely
identified phosphopeptides corresponding to 425 proteins and identified several
not previously described phosphorylation motifs. A subset of 45 phosphoproteins
was defined as being significantly changed in abundance upon Fe deficiency.
Kinase motifs in Fe-responsive proteins matched to protein kinase A/calcium
calmodulin-dependent kinase II, casein kinase II, and proline-directed kinase,
indicating a possible critical function of these kinase classes in Fe
homeostasis. To validate our analysis, we conducted site-directed mutagenesis on
IAA-CONJUGATE-RESISTANT4 (IAR4), a protein putatively functioning in auxin
homeostasis. iar4 mutants showed compromised root hair formation and developed
shorter primary roots. Changing serine-296 in IAR4 to alanine resulted in a
phenotype intermediate between mutant and wild type, whereas acidic substitution
to aspartate to mimic phosphorylation was either lethal or caused an extreme
dwarf phenotype, supporting the critical importance of this residue in Fe
homeostasis. Our analyses further disclose substantial changes in the abundance
of phosphoproteins involved in primary carbohydrate metabolism upon Fe
deficiency, complementing the picture derived from previous proteomic and
transcriptomic profiling studies.
DOI: 10.1104/pp.112.193987
PMCID: PMC3375974
PMID: 22438062 [Indexed for MEDLINE]
