Abstract
Nitrogen is an essential macronutrient for plant growth and development. Inorganic nitrogen and its assimilation products control various metabolic, physiological and developmental processes. Although the transcriptional responses induced by nitrogen have been extensively studied in the past, our work here focused on the discovery of candidate proteins for regulatory events that are complementary to transcriptional changes. Most signaling pathways involve modulation of protein abundance and/or activity by protein phosphorylation. Therefore, we analyzed the dynamic changes in protein phosphorylation in membrane and soluble proteins from plants exposed to rapid changes in nutrient availability over a time course of 30 min. Plants were starved of nitrogen and subsequently resupplied with nitrogen in the form of nitrate or ammonium. Proteins with maximum change in their phosphorylation level at up to 5 min after nitrogen resupply (fast responses) included GPI-anchored proteins, receptor kinases and transcription factors, while proteins with maximum change in their phosphorylation level after 10 min of nitrogen resupply (late responses) included proteins involved in protein synthesis and degradation, as well as proteins with functions in central metabolism and hormone metabolism. Resupply of nitrogen in the form of nitrate or ammonium resulted in distinct phosphorylation patterns, mainly of proteins with signaling functions, transcription factors and transporters.
Highlights
As sessile organisms, plants need to rapidly adapt to changes in the environment such as light fluctuations and alterations in nutrient availability
The transcriptional responses induced by nitrogen have been extensively studied in the past, our work here focused on the discovery of candidate proteins for regulatory events that are complementary to transcriptional changes
We analyzed the dynamic changes in protein phosphorylation in membrane and soluble proteins from plants exposed to rapid changes in nutrient availability over a time course of 30 min
Summary
Plants need to rapidly adapt to changes in the environment such as light fluctuations and alterations in nutrient availability. Plants have the potential for adaptation to reduced nitrogen availability by increasing the capacity for nutrient acquisition and by alteration of wholeplant morphology and metabolism, such as increasing the root/shoot ratio or anthocyanin accumulation in leaves (Rubio et al, 2009). Developmental adaptive mechanisms stimulate growth in organs that directly participate in nutrient acquisition, such as primary roots (Walch-Liu and Forde, 2008). To trigger these adaptive responses and to induce fast. Nitrate regulates the expression of genes involved in carbon metabolism, thereby coordinating the production of organic acids required for inorganic nitrogen assimilation (Gutierrez et al, 2007)
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