Abstract
Agricultural nitrous oxide (N2O) pollution resulting from the use of synthetic fertilizers represents a significant contribution to anthropogenic greenhouse gas emissions, providing a rationale for reduced use of nitrogen (N) fertilizers. Nitrogen limitation results in extensive systems rebalancing that remodels metabolism and defence processes. To analyse the regulation underpinning these responses, barley (Horedeum vulgare) seedlings were grown for 7 d under N-deficient conditions until net photosynthesis was 50% lower than in N-replete controls. Although shoot growth was decreased there was no evidence for the induction of oxidative stress despite lower total concentrations of N-containing antioxidants. Nitrogen-deficient barley leaves were rich in amino acids, sugars and tricarboxylic acid cycle intermediates. In contrast to N-replete leaves one-day-old nymphs of the green peach aphid (Myzus persicae) failed to reach adulthood when transferred to N-deficient barley leaves. Transcripts encoding cell, sugar and nutrient signalling, protein degradation and secondary metabolism were over-represented in N-deficient leaves while those associated with hormone metabolism were similar under both nutrient regimes with the exception of mRNAs encoding proteins involved in auxin metabolism and responses. Significant similarities were observed between the N-limited barley leaf transcriptome and that of aphid-infested Arabidopsis leaves. These findings not only highlight significant similarities between biotic and abiotic stress signalling cascades but also identify potential targets for increasing aphid resistance with implications for the development of sustainable agriculture.
Highlights
Agricultural production is estimated to contribute approximately 10–12% of total anthropogenic greenhouse gas emissions (Burney et al, 2010)
Leaf chlorophyll and protein were more responsive than net photosynthesis at the early stages of nitrogen limitation
RNA was extracted from leaves of four individual barley plants treated in parallel to those used for metabolite profiling as described by Kerchev et al (2011)
Summary
Agricultural production is estimated to contribute approximately 10–12% of total anthropogenic greenhouse gas emissions (Burney et al, 2010). The most significant contribution to agricultural emissions arises from the production and use of nitrogen (N) fertilizers. Haber-Bosch process for N fixation accounts for more than 50% of the total energy use in commercial agriculture (Woods et al, 2010). N fertilization of agricultural soils results in sharply increased emissions of nitrous oxide (N2O). This greenhouse gas has almost 300 times the warming. Potential of CO2 (Shcherbak et al, 2014) and represents almost 40% of direct agricultural greenhouse gas emissions (Burney et al, 2010). There is a clear rationale for the reduction of N use within agricultural production
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