Adaptive responses of amino acid metabolism to the combination of desiccation and low nitrogen availability in Sporobolus stapfianus

Authors: YOBI, ABOU - University Of Missouri; BATUSHANSKY, ALBERT - University Of Missouri; Oliver, Melvin; ANGELOVICI, RUTHIE - University Of Missouri

Submitted to: Planta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/29/2019
Publication Date: 2/6/2019
Publication URL: http://handle.nal.usda.gov/10113/6373087
Citation: Yobi, A., Batushansky, A., Oliver, M.J., Angelovici, R. 2019. Adaptive responses of amino acid metabolism to the combination of desiccation and low nitrogen availability in Sporobolus stapfianus. Planta. 249(5):1535-1549. https://doi.org/10.1007/s00425-019-03105-6.
DOI: https://doi.org/10.1007/s00425-019-03105-6

Interpretive Summary: Drought is the leading factor for crop loss worldwide and, when coupled with excess heat, salinity, cold, or nutrient stress could severely threaten agriculture. Our understanding of how combinations of stress effectors impact plants is still limited, but it is clear that combinations of stresses illicit responses that cannot be predicted from the response to a single stress. Understanding how plants adapt to combinations of stress is critical for crop improvement strategies. Crops have been of limited value for understanding the physiological and evolutionary processes that make possible plant adaptations to combinations of stress because they originate generally in benign environments. In this report we looked at how the grass Sporobolus stapfianus, a forage grass adapted to extreme environments, responds to a combination of dehydration and low-nitrogen availability in the soil. Our study demonstrated that, during desiccation, small portions of both free fatty acids (not in proteins) and protein-bound amino acids are mobilized from underground tissues, mainly roots, for usage when nitrogen is abundant, while large protein-bound amino acid turnover in mature leaves serves as the main source for amino acid remobilization under low nitrogen. These studies have important implications for growing plants under drought and in poor soils and inform our efforts to improve stress tolerance in major grass crops, such as maize and sorghum.

Technical Abstract: Sporobolus stapfianus has adapted to stressful habitats that expose it to a combination of desiccation and low-nitrogen availability. The mechanisms that underpin the adaptation of S. stapfianus to desiccation have been extensively studies and it was repeatedly demonstrated that amino acid metabolism plays an important role. However, the interplay between desiccation and low nitrogen is unknown. To examine the combined effect of these two stressors on amino acid metabolism, we used a targeted metabolic approach to quantify the absolute levels of free and protein-bound amino acids (FAA and PBAA), and their gamma-glutamyl (gg-AA) derivatives in four S. stapfianus tissues and under two nitrogen regimes. Our study demonstrates that nitrogen availability in the hydrated state is what dictates nitrogen metabolism during desiccation. When nitrogen is high, underground tissues, mainly roots, serve as the source for FAAs and PBAAs remobilization during drying, while huge PBAAs turnover in mature leaves serves as the main source for remobilization under low nitrogen. As the substantial reduction in these fractions in roots and mature leaves is not manifested in immature leaves, we suggest that these amino acids are further metabolized to support rearrangement in central metabolism that are essential for the acquisition of desiccation tolerance (DT).