Molecular & Cellular Proteomics
Volume 9, Issue 9, September 2010, Pages 2019-2033
Journal home page for Molecular & Cellular Proteomics

Research
Comparative Proteomics Indicates That Biosynthesis of Pectic Precursors Is Important for Cotton Fiber and Arabidopsis Root Hair Elongation*

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The quality of cotton fiber is determined by its final length and strength, which is a function of primary and secondary cell wall deposition. Using a comparative proteomics approach, we identified 104 proteins from cotton ovules 10 days postanthesis with 93 preferentially accumulated in the wild type and 11 accumulated in the fuzzless-lintless mutant. Bioinformatics analysis indicated that nucleotide sugar metabolism was the most significantly up-regulated biochemical process during fiber elongation. Seven protein spots potentially involved in pectic cell wall polysaccharide biosynthesis were specifically accumulated in wild-type samples at both the protein and transcript levels. Protein and mRNA expression of these genes increased when either ethylene or lignoceric acid (C24:0) was added to the culture medium, suggesting that these compounds may promote fiber elongation by modulating the production of cell wall polymers. Quantitative analysis revealed that fiber primary cell walls contained significantly higher amounts of pectin, whereas more hemicellulose was found in ovule samples. Significant fiber growth was observed when UDP-l-rhamnose, UDP-d-galacturonic acid, or UDP-d-glucuronic acid, all of which were readily incorporated into the pectin fraction of cell wall preparations, was added to the ovule culture medium. The short root hairs of Arabidopsis uer1-1 and gae6-1 mutants were complemented either by genetic transformation of the respective cotton cDNA or by adding a specific pectin precursor to the growth medium. When two pectin precursors, produced by either UDP-4-keto-6-deoxy-d-glucose 3,5-epimerase 4-reductase or by UDP-d-glucose dehydrogenase and UDP-d-glucuronic acid 4-epimerase successively, were used in the chemical complementation assay, wild-type root hair lengths were observed in both cut1 and ein2-5 Arabidopsis seedlings, which showed defects in C24:0 biosynthesis or ethylene signaling, respectively. Our results suggest that ethylene and C24:0 may promote cotton fiber and Arabidopsis root hair growth by activating the pectin biosynthesis network, especially UDP-l-rhamnose and UDP-d-galacturonic acid synthesis.

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*

This work was supported by China National Basic Research Program Grant 2004CB117302, National Natural Science Foundation of China Grant 90717009, the 111 project from the Chinese Ministry of Education, and a Natural Sciences and Engineering Research Council of Canada discovery grant (to T. L. W.).

This article contains supplemental Tables 1–4, Figs. 1–9, and Spectra 1 and 2.

1

The abbreviations used are:

    dpa

    days postanthesis

    UER

    UDP-4-keto-6-deoxy-d-glucose 3,5-epimerase 4-reductase

    UGP

    UDP-d-glucose pyrophosphorylase

    UGD

    UDP-d-glucose dehydrogenase

    GAE

    UDP-d-glucuronic acid 4-epimerase

    Rha

    l-rhamnose

    Xyl

    d-xylose

    GalA

    d-galacturonic acid

    GlcA

    d-glucuronic acid

    2-DE

    two-dimensional gel electrophoresis

    fl

    fuzzless-lintless

    S/N

    signal to noise ratio

    RACE

    rapid amplification of 5′ or 3′ cDNA ends

    BLAST

    basic local alignment search tool

    FDR

    false discovery rate

    QRT-PCR

    quantitative real time RT-PCR

    At

    Arabidopsis thaliana

    Gh

    G. hirsutum

    4K6DG

    4-keto-6-deoxyglucose

    AVG

    l-(2-aminoethoxyvinyl)glycine hydrochloride

    KEGG

    Kyoto Encyclopedia of Genes and Genomes

    RHM

    rhamnose synthase

    NCBI

    National Center for Biotechnology Information

    UGE

    UDP-glucose 4-epimerase.

Both authors contributed equally to this work.