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Research Project: Developing Soybean and Other Legumes with Resistance to Pathogens and Assessing the Biosafety of Transgenic Soybean

Location: Soybean Genomics & Improvement Laboratory

Title: The proteomics of nitrogen remobilization in poplar bark

Author
item ISLAM, NAZRUL - University Of Maryland
item GEN, LI - University Of Maryland
item Garrett, Wesley
item LIN, RONGSHUANG - University Of Maryland
item SRIRAM, GANESH - University Of Maryland
item Cooper, Bret
item COLEMAN, GARY - University Of Maryland

Submitted to: Journal of Proteome Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/16/2014
Publication Date: 12/16/2015
Publication URL: http://handle.nal.usda.gov/10113/61531
Citation: Islam, N., Gen, L., Garrett, W.M., Lin, R., Sriram, G., Cooper, B., Coleman, G.D. 2015. The proteomics of nitrogen remobilization in poplar bark. Journal of Proteome Research. 14:1112-1126.

Interpretive Summary: Poplar trees grow and produce biomass quickly, which makes them an important biofuel feedstock. Poplar trees efficiently recycle nitrogen, meaning that less nitrogen fertilizer needs to be applied to grow the trees for fuel. Consequently, this translates to less energy input and greater energy output. Thus, nitrogen recycling is an important factor in choosing biofuel feedstocks, but little is known about how poplar trees recycle nitrogen. Evidence shows that poplar stores and recycles nitrogen in its proteins. Therefore, we used mass spectrometry to identify poplar proteins during stages of cell growth when nitrogen is recycled. We identified for the first time several protease proteins that degrade nitrogen storage proteins. The proteases were activated during stages of new growth. It is likely that the amino acids liberated from degraded proteins are recycled to produce new proteins that support tree growth in the spring time. These results provide new insight into nitrogen recycling in poplar. These data are most likely to influence scientists at universities, government agencies and companies who are studying biofuels and energy efficiency.

Technical Abstract: Seasonal nitrogen (N) cycling in temperate deciduous trees involves the accumulation of bark storage proteins (BSPs), a class of vegetative storage proteins in phloem parenchyma and xylem ray cells. BSPs are anabolized using recycled N in the form of amino acids after autumn leaf senescence and later become a source of N during spring shoot growth as they are catabolized. Although progress has been made in understanding the mechanisms involved in N cycling, little is known about the processes involved in remobilization and reutilization of N in trees. In this study, we used multidimensional protein identification technology (MudPIT) and spectral counting to identify protein accumulation changes that occur in the bark during BSP catabolism. A total of 4,178 proteins were identified from bark prior to and during BSP catabolism. The majority (62%) of the proteins were found during BSP catabolism, indicating extensive remodeling of the proteome during renewed shoot growth and N remobilization. Among these proteins were 30 proteases, the relative abundances of which increased during BSP catabolism. These proteases spanned a range of families including members of the papain-like cysteine proteases, serine carboxypeptidases and aspartyl proteases. These data identify, for the first time, candidate proteases that could potentially provide hydrolase activity required for N remobilization from BSPs. These results provide the foundation for research to advance our knowledge of poplar, an important forest tree crop and biofuel feedstock.