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Two winter wheat (Triticum aestivum L.) populations, i.e. 180 genetic resources and 210 elite varieties, were compared in a field trial to analyse how grain number and grain yield distribution along the spike changed during the breeding process and how this associates to yield-related traits. Elites showed in average 38% more yield compared to resources. This breeding improvement mainly derived from an increase in grains and yield per spike in addition to grains and yield per spikelet. These increments corresponded to 19, 23, 21 and 25%, respectively. Not much gain in thousand grain weight (4%) was observed in elites as compared to resources. The number of spikelets per spike was not, or even negatively, correlated with most traits, except of grains per spike, which suggests that this trait was not favoured during breeding. The grain number and grain yield distributions along the spike (GDAS and GYDAS) were measured and compared by using a novel mathematical tool. GDAS and GYDAS measure the deviation of a spike of interest from the architecture of a model spike with even grain and yield distribution along all spikelets, respectively. Both traits were positively correlated. Elites showed in average only a 1% improvement in GDAS and GYDAS values compared to resources. This comparison revealed that breeding increased grain number and yield uniformly along the spike without changing relative yield input of individual spikelets, thereby, maintaining the general spike architecture. [ABSTRACT FROM AUTHOR]

Summary The barley Risø16 mutation leads to inactivation of cytosolic ADP-Glc pyrophosphorylase, and results in decreased ADP-Glc and endospermal starch levels. Here we show that this mutation is accompanied by a decrease in storage protein accumulation and seed size, which indicates that alteration of a single enzymatic step can change the network of storage metabolism as a whole. We used comprehensive transcript, metabolite and hormonal profiling to compare grain metabolism and development of Risø16 and wild-type endosperm. Despite increased sugar availability in mutant endosperm, glycolytic intermediates downstream of hexose phosphates remained unchanged or decreased, while several glycolytic enzymes were downregulated at the transcriptional level. Metabolite and transcript profiling also indicated an inhibition of the tricarboxylic acid cycle at the level of mitochondrial nicotinamide adenine dinucleotide (NAD)-isocitrate dehydrogenase and an attendant decrease in alpha-ketoglutarate and amino acids levels in Risø16, compared with wild type. Decreased levels of cytokinins in Risø16 endosperm suggested co-regulation between starch synthesis, abscisic acid (ABA) deficiency and cytokinin biosynthesis. Comparative cis-element analysis in promoters of jointly downregulated genes in Risø16 revealed an overlap between metabolic and hormonal regulation, which leds to a coordinated downregulation of endosperm-specific and ABA-inducible gene expression (storage proteins) together with repression by sugars (isocitrate dehydrogenase, amylases). Such co-regulation ensured that decreased carbon fluxes into starch lead to a coordinated inhibition of glycolysis, amino acid and storage proteins biosynthesis, which is useful in the prevention of osmotic imbalances and oxidative stress due to increased accumulation of sugars. [ABSTRACT FROM AUTHOR]

The application of nitrogen to legumes regulates seed metabolism and composition. We recently showed that the seed-specific overexpression of amino acid permease VfAAP1 increases amino acid supply, and the levels of N and protein in the seeds. Two consecutive field trials using Pisum sativum AAP1 lines confirmed increases in the levels of N and globulin in seed; however, compensatory changes of sucrose/starch and individual seed weight were also observed. We present a comprehensive analysis of AAP1 seeds using combinatorial transcript and metabolite profiling to monitor the effects of nitrogen supply on seed metabolism. AAP1 seeds have increased amino acids and stimulated gene expression associated with storage protein synthesis, maturation, deposition and vesicle trafficking. Transcript/metabolite changes reveal the channelling of surplus N into the transient storage pools asparagine and arginine, indicating that asparagine synthase is transcriptionally activated by high N levels and/or C limitation. Increased C-acceptor demand for amino acid synthesis, resulting from elevated levels of N in seeds, initiates sucrose mobilization and sucrose-dependent pathways via sucrose synthase, glycolysis and the TCA cycle. The AAP1 seeds display a limitation in C, which leads to the catabolism of arginine, glutamic acid and methionine to putrescine, β-alanine and succinate. Mitochondria are involved in the coordination of C/N metabolism, with branched-chain amino acid catabolism and a γ-amino-butyric acid shunt. AAP1 seeds contain higher levels of ABA, which is possibly involved in storage-associated gene expression and the N-dependent stimulation of sucrose mobilization, indicating that a signalling network of C, N and ABA is operating during seed maturation. These results demonstrate that legume seeds have a high capacity to regulate N:C ratios, and highlight the importance of mitochondria in the control of N–C balance and amino acid homeostasis. [ABSTRACT FROM AUTHOR]