Establishment of a Protein Reference Map for Soybean Root Hair Cells

Authors: BRECHENMACHER, LAURENT - UNIVERSITY OF MISSOURI; LEE, JOOHYUN - KOREA; SACHDEV, SHERRI - UNIVERSITY OF MISSOURI; SONG, ZHAO - UNIVERSITY OF MISSOURI; NGUYEN, THRA HONG NHA - UNIVERSITY OF MISSOURI; JOSHI, TRUPTI - UNIVERSITY OF MISSOURI; OEHRLE, NATHAN - UNIVERSITY OF MISSOURI; LIBAULT, MARC - UNIVERISTY OF MISSOURI; MOONEY, BRIAN - UNIVERSITY OF MISSOURI; XU, DONG - UNIVERSITY OF MISSOURI; Cooper, Bret; STACEY, GARY - UNIVERSITY OF MISSOURI

Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2009
Publication Date: 2/1/2009
Citation: Brechenmacher, L., Lee, J., Sachdev, S., Song, Z., Nguyen, T., Joshi, T., Oehrle, N., Libault, M., Mooney, B., Xu, D., Cooper, B., Stacey, G. 2009. Establishment of a Protein Reference Map for Soybean Root Hair Cells. Plant Physiology. 149:670-68.

Interpretive Summary: Soybean roots have millions of single cell hairs on them that increase surface area and enhance water uptake. These root hairs are also the sites of Rhizobium bacterial infection that allows the plant to produce its own nitrogen and live without added fertilizer. It is believed that a set of proteins makes root hairs unique from other parts of the plant such as a leaf, but it is unknown what these unique proteins are. Experiments were designed to purify single cell root hairs and isolate proteins from them. The proteins were separated from each other and they were each identified by their unique size using a mass spectrometer. 1,492 different proteins were identified and some of these proteins, including some that might serve as water channels, appeared to be unique to root hairs. These data are most likely to be useful to scientists at universities, government agencies, and private and public institutes and companies who are trying to improve drought resistance and nitrogen production in soybeans.

Technical Abstract: Root hairs are single tubular cells formed from the differentiation of epidermal cells on roots. They are involved in water and nutrient uptake, and represent the infection site on leguminous roots by rhizobia, soil bacteria that establish a nitrogen fixing symbiosis. Root hairs develop by polar cell expansion or tip growth, a unique mode of plant growth shared only with pollen tubes. A more complete characterization of root hair cell biology will lead to a better understanding of tip growth, the rhizobial infection process and also lead to improvements in plant water and nutrient uptake. We analyzed the proteome of isolated soybean root hair cells using two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and shotgun proteomics approaches. Soybean was selected for this study due to its agronomic importance and its root size. The resulting soybean root hair proteome reference map identified 1,492 different proteins. 2D-PAGE followed by mass spectrometry identified 527 proteins from total cell contents. A complementary shotgun analysis identified 1,134 total proteins, including 443 proteins that were specific to the root hair microsome fraction. Only 169 proteins were identified by the 2D-PAGE and shotgun methods, which highlights the advantage of using both methods in proteomics analysis. The proteins identified are involved not only in basic cell metabolism, but also in functions more specific to the single root hair cell, including water and nutrient uptake, vesicle trafficking, hormone and secondary metabolism. The data presented provides useful insight into the metabolic activities of a single, differentiated plant cell type.