A pathway-specific microarray analysis highlights the complex and co-ordinated transcriptional networks of the developing grain of field-grown barley

The aim of the study was to describe the molecular and biochemical interactions associated with amino acid biosynthesis and storage protein accumulation in the developing grains of field-grown barley. Our strategy was to analyse the transcription of genes associated with the biosynthesis of storage products during the development of field-grown barley grains using a grain-specific microarray assembled in our laboratory. To identify co-regulated genes, a distance matrix was constructed which enabled the identification of three clusters corresponding to early, middle, and late grain development. The gene expression pattern associated with the clusters was investigated using pathway-specific analysis with specific reference to the temporal expression levels of a range of genes involved mainly in the photosynthesis process, amino acid and storage protein metabolism. It is concluded that the grain-specific microarray is a reliable and cost-effective tool for monitoring temporal changes in the transcriptome of the major metabolic pathways in the barley grain. Moreover, it was sensitive enough to monitor differences in the gene expression profiles of different homologues from the storage protein families. The study described here should provide a strong complement to existing knowledge assisting further understanding of grain development and thereby provide a foundation for plant breeding towards storage proteins with improved nutritional quality

Breeding for increased nitrogen-use efficiency: a review for wheat (T. aestivum L.)

Nitrogen fertilizer is the most used nutrient source in modern agriculture and represents significant environmental and production costs. In the meantime, the demand for grain increases and production per area has to increase as new cultivated areas are scarce. In this context, breeding for an efficient use of nitrogen became a major objective. In wheat, nitrogen is required to maintain a photosynthetically active canopy ensuring grain yield and to produce grain storage proteins that are generally needed to maintain a high end-use quality. This review presents current knowledge of physiological, metabolic and genetic factors influencing nitrogen uptake and utilization in the context of different nitrogen management systems. This includes the role of root system and its interactions with microorganisms, nitrate assimilation and its relationship with photosynthesis as postanthesis remobilization and nitrogen partitioning. Regarding nitrogen-use efficiency complexity, several physiological avenues for increasing it were discussed and their phenotyping methods were reviewed. Phenotypic and molecular breeding strategies were also reviewed and discussed regarding nitrogen regimes and genetic diversity

Etude agronomique, physiologique et cytologique de la remobilisation de l'azote au cours de la phase de remplissage du grain chez le blé tendre d'hiver (Triticum aestivum L.)

AMIENS-BU Sciences (800212103) / SudocSudocFranceF

Foliar nitrogen application in wheat: the effects on grain N content, recovery of fertilizer and the response of cytosolic glutamine synthetase

Foliar application of N fertilizer is an efficient strategy with respect to boosting grain protein content and matching plant N demand with the actual climatic conditions in the growing season. However, foliar N application implies the risk of leaf damage. We would like to develop wheat genotypes that are better suited for foliar N fertilization. Therefore, wheat plants were subjected to different fertilization regimes including foliar application of N to investigate the effect on plant growth and molecular-physiological parameters related to nitrogen use efficiency. Using 15N as a tracer, we have observed that an unexpected large proportion (about 50%) of the N applied to the leaves remained in the vegetative plant parts at maturity, suggesting a bottleneck in the translocation of N to the grain. As cytosolic glutamine synthetase is a central enzyme in the assimilation and translocation of N from the leaves to the grain, we analysed GS activity and protein levels. GS activity in flag leaf increased in response to foliar application of N although the levels of GS protein were similar for the different treatments and growth stages during grain filling. Currently, GS gene expression is under investigation using Q-PCR

A seasonal study of nitrogen status in Miscanthus giganteus highlights a central role for asparagine and arginine

CT 2 ; Département BAPA seasonal study of nitrogen status in Miscanthus giganteus highlights a central role for asparagine and arginine. EMBO conference : the nitrogen nutrition of plants – Nitrogen 201

Leaf Scorching following Foliar Fertilization of Wheat with Urea or Urea–Ammonium Nitrate Is Caused by Ammonium Toxicity

Foliar fertilization is a potential tool to increase the use-efficiency of nitrogen (N) fertilizers. However, whilst leaf scorching has frequently been reported, the underlying physiological processes are not clear. In the present work, we investigate the intensity of leaf scorching as affected by the balance between ammonium assimilation and accumulation. Leaves were sprayed with urea–ammonium nitrate (UAN) solution without surfactant or applied liquid droplets of urea in different N concentrations with surfactant. UAN solutions without surfactant containing >10% N caused leaf scorching already after 24 h and the severity increased with the N concentration. The same pattern was observed 3 days after the application of urea solutions containing >4% N together with surfactant. The scorching was accompanied by a massive increase in foliar and apoplastic ammonium (NH4+) concentration. Moreover, the activity of glutamine synthetase (GS), most pronouncedly that of the chloroplastic isoform (GS2), decreased a few hours after the application of high N-concentrations. Along with this, the concentration of glutamate—the substrate for GS—decreased. We conclude that leaf scorching is promoted by NH4+ accumulation due to a limitation in N assimilation capacity