Nitrous oxide (N(2)O) is a key atmospheric greenhouse gas that contributes to global climatic change through radiative warming and depletion of stratospheric ozone. In this report, N(2)O flux was monitored simultaneously with photosynthetic CO(2) and O(2) exchanges from intact canopies of 12 wheat seedlings. The rates of N(2)O-N emitted ranged from <2 pmol x m(-2) x s(-1) when NH(4)(+) was the ...

The ecological prominence of diatoms in the ocean environment largely results from their superior competitive ability for dissolved nitrate (NO3-). To investigate the cellular and genetic basis of diatom NO3- assimilation, we generated a knockout in the nitrate reductase gene (NR-KO) of the model pennate diatom Phaeodactylum tricornutum In NR-KO cells, N-assimilation was abolished although NO3-...

Crop plant development is strongly dependent on the availability of nitrogen (N) in the soil and the efficiency of N utilization for biomass production and yield. However, knowledge about molecular responses to N deprivation derives mainly from the study of model species. In this article, the metabolic adaptation of source leaves to low N was analyzed in maize (Zea mays) seedlings by parallel m...

The nitrogen cycle describes the processes through which nitrogen is converted between its various chemical forms. These transformations involve both biological and abiotic redox processes. The principal processes involved in the nitrogen cycle are nitrogen fixation, nitrification, nitrate assimilation, respiratory reduction of nitrate to ammonia, anaerobic ammonia oxidation (anammox) and denit...

The unicellular red alga Cyanidioschyzon merolae is a model organism for studying the basic biology of photosynthetic organisms. The C. merolae cell is composed of an extremely simple set of organelles. The genome is completely sequenced. Gene targeting and a heat-shock inducible gene expression system has been recently established. However, a conditional gene knockdown system has not been esta...

Diatoms are unicellular algae that accumulate significant amounts of triacylglycerols as storage lipids when their growth is limited by nutrients. Using biochemical, physiological, bioinformatics, and reverse genetic approaches, we analyzed how the flux of carbon into lipids is influenced by nitrogen stress in a model diatom, Phaeodactylum tricornutum. Our results reveal that the accumulation o...

Even in nitrogen-replete ecosystems, microhabitats exist where local-scale nutrient limitation occurs. For example, coastal waters of the northeastern Pacific Ocean are characterized by high nitrate concentrations associated with upwelling. However, macroalgae living in high-zone tide pools on adjacent rocky shores are isolated from this upwelled nitrate for extended periods of time, leading to...

The Nicotiana sylvestris mutant, CMS, lacks the mitochondrial gene nad7 and functional complex I, and respires using low-affinity NADH (alternative) mitochondrial dehydrogenases. Here, we show that this adjustment of respiratory pathways is associated with a profound modification of foliar carbon-nitrogen balance. CMS leaves are characterized by abundant amino acids compared to either wild-type...