Article

The Mucilage Proteome of Maize (Zea mays L.) Primary Roots

Department of Plant Nutrition, China Agricultural University, Beijing, PR China.
Journal of Proteome Research (Impact Factor: 5). 06/2010; 9(6):2968-76. DOI: 10.1021/pr901168v
Source: PubMed

ABSTRACT Maize (Zea mays L.) root cap cells secrete a large variety of compounds including proteins via an amorphous gel structure called mucilage into the rhizosphere. In the present study, mucilage secreted by primary roots of 3-4 day old maize seedlings was collected under axenic conditions, and the constitutively secreted proteome was analyzed. A total of 2848 distinct extracellular proteins were identified by nanoLC-MS/MS. Among those, metabolic proteins (approximately 25%) represented the largest class of annotated proteins. Comprehensive sets of proteins involved in cell wall metabolism, scavenging of reactive oxygen species, stress response, or nutrient acquisition provided detailed insights in functions required at the root-soil interface. For 85-94% of the mucilage proteins previously identified in the relatively small data sets of the dicot species pea, Arabidopsis, and rapeseed, a close homologue was identified in the mucilage proteome of the monocot model plant maize, suggesting a considerable degree of conservation between mono and dicot mucilage proteomes. Homologues of a core set of 12 maize proteins including three superoxide dismutases and four chitinases, which provide protection from fungal infections, were present in all three mucilage proteomes investigated thus far in the dicot species Arabidopsis, rapeseed, and pea and might therefore be of particular importance.

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    • "These proteins are believed to play an important role in the rhizosphere and a relatively high number (54%) had predicted signal peptides. Ma et al. (2010) collected proteins secreted in the mucilage of primary maize roots. Using a combination of 1D SDS-PAGE and HPLC-MS/MS, the presence of 2848 proteins were reported, which is over 50 times more compared to earlier quantitative studies of root mucilage based on 2D-PAGE or MudPIT (Basu et al., 2006; Wen et al., 2007). "
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    • "However, it was not possible to detect ear preferential fungal infection (Fig. 5B). Previously, a large number of proteins related to plant defence or diseases were detected in root mucilage even if all maize plants were healthy and grown in an axenic environment (Ma et al., 2010). Therefore, it was concluded that nitrogen nutritional imbalance, rather than bacterial or fungal pathogen infection, resulted in significant differential accumulation of proteins related to plant defence in the present study. "
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