Proteomic analysis of shoot-borne root initiation in maize (Zea mays L.)

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Abstract
Postembryonically formed shoot‐borne roots make up the major backbone of the adult maize root stock. In this study the abundant soluble proteins of the first node (coleoptilar node) of wild‐type and mutant rtcs seedlings, which do not initiate crown roots, were compared at two early stages of crown root formation. In Coomassie Bluestained 2‐D gels, representing soluble proteins of coleoptilar nodes 5 and 10 days after germination, 146 and 203 proteins were detected, respectively. Five differentially accumulated proteins (>two‐fold change; t‐test: 95% significance) were identified in 5‐day‐old and 14 differentially accumulated proteins in 10‐day‐old coleoptilar nodes of wild‐type versus rtcs. All 19 differentially accumulated proteins were identified via ESI MS/MS mass spectrometry. Five differentially accumulated proteins, including a regulatory G‐protein and a putative auxin‐binding protein, were further analyzed at the RNA expression level. These experiments confirmed differential gene expression and revealed subtle developmental regulation of these genes during early coleoptilar node development. This study represents the first proteomic analysis of shoot‐borne root initiation in cereals and will contribute to a better understanding of the molecular basis of this developmental process unique to cereals.