Wheat yield potential can be maximized by increasing red to far-red light conditions at critical developmental stages.

Sensing of neighbours via the Red to Far-Red light ratio (R:FR) may exert a cap to yield potential in wheat. The effects of an increased R:FR inside the canopy were studied in dense wheat mini canopies grown in controlled environments by lowering FR. To distinguish between effects exerted by light sensing and assimilate supply, the treatments were complemented with elevated CO2 , applied between different developmental timepoints to specifically impact tillering, spike growth, floret fertility and grain filling, in different combinations. The yield response to high R:FR was strongly dependent on the developmental stage in all three cultivars and pivoted between positive if applied after the start of stem elongation, and negative or null if applied before. Yield gains of up to 70% and 120% were observed, respectively, in two cultivars, associated with a higher number of tiller spikes and grains per spike in the main shoot. The response to the combination of high R:FR and elevated CO2 or CO2 alone were cultivar dependent. Taken together, our results suggest that R:FR exerts a significant control on yield potential in wheat and achieving a high R:FR from stem elongation to maturity is a promising lever towards a significant increase in grain yield.

Cellular Plasticity in Response to Suppression of Storage Proteins in the Brassica napus Embryo.

The tradeoff between protein and oil storage in oilseed crops has been tested here in oilseed rape (Brassica napus) by analyzing the effect of suppressing key genes encoding protein storage products (napin and cruciferin). The phenotypic outcomes were assessed using NMR and mass spectrometry imaging, microscopy, transcriptomics, proteomics, metabolomics, lipidomics, immunological assays, and flux balance analysis. Surprisingly, the profile of storage products was only moderately changed in RNA interference transgenics. However, embryonic cells had undergone remarkable architectural rearrangements. The suppression of storage proteins led to the elaboration of membrane stacks enriched with oleosin (sixfold higher protein abundance) and novel endoplasmic reticulum morphology. Protein rebalancing and amino acid metabolism were focal points of the metabolic adjustments to maintain embryonic carbon/nitrogen homeostasis. Flux balance analysis indicated a rather minor additional demand for cofactors (ATP and NADPH). Thus, cellular plasticity in seeds protects against perturbations to its storage capabilities and, hence, contributes materially to homeostasis. This study provides mechanistic insights into the intriguing link between lipid and protein storage, which have implications for biotechnological strategies directed at improving oilseed crops.

Metabolism of polysaccharides in dynamic middle lamellae during cotton fibre development.

MAIN CONCLUSION: Evidence is presented that cotton fibre adhesion and middle lamella formation are preceded by cutin dilution and accompanied by rhamnogalacturonan-I metabolism. Cotton fibres are single cell structures that early in development adhere to one another via the cotton fibre middle lamella (CFML) to form a tissue-like structure. The CFML is disassembled around the time of initial secondary wall deposition, leading to fibre detachment. Observations of CFML in the light microscope have suggested that the development of the middle lamella is accompanied by substantial cell-wall metabolism, but it has remained an open question as to which processes mediate adherence and which lead to detachment. The mechanism of adherence and detachment were investigated here using glyco-microarrays probed with monoclonal antibodies, transcript profiling, and observations of fibre auto-digestion. The results suggest that adherence is brought about by cutin dilution, while the presence of relevant enzyme activities and the dynamics of rhamnogalacturonan-I side-chain accumulation and disappearance suggest that both attachment and detachment are accompanied by rhamnogalacturonan-I metabolism.

Heteromannan and Heteroxylan Cell Wall Polysaccharides Display Different Dynamics During the Elongation and Secondary Cell Wall Deposition Phases of Cotton Fiber Cell Development.

The roles of non-cellulosic polysaccharides in cotton fiber development are poorly understood. Combining glycan microarrays and in situ analyses with monoclonal antibodies, polysaccharide linkage analyses and transcript profiling, the occurrence of heteromannan and heteroxylan polysaccharides and related genes in developing and mature cotton (Gossypium spp.) fibers has been determined. Comparative analyses on cotton fibers at selected days post-anthesis indicate different temporal and spatial regulation of heteromannan and heteroxylan during fiber development. The LM21 heteromannan epitope was more abundant during the fiber elongation phase and localized mainly in the primary cell wall. In contrast, the AX1 heteroxylan epitope occurred at the transition phase and during secondary cell wall deposition, and localized in both the primary and the secondary cell walls of the cotton fiber. These developmental dynamics were supported by transcript profiling of biosynthetic genes. Whereas our data suggest a role for heteromannan in fiber elongation, heteroxylan is likely to be involved in the regulation of cellulose deposition of secondary cell walls. In addition, the relative abundance of these epitopes during fiber development varied between cotton lines with contrasting fiber characteristics from four species (G. hirsutum, G. barbadense, G. arboreum and G. herbaceum), suggesting that these non-cellulosic polysaccharides may be involved in determining final fiber quality and suitability for industrial processing.

Transcript profiling during fiber development identifies pathways in secondary metabolism and cell wall structure that may contribute to cotton fiber quality.

A global gene expression profiling study at different stages of fiber development was undertaken on two cotton species cultivated for fiber, Gossypium hirsutum (L.) and G. barbadense (L.). A large proportion of the genome was expressed during both fiber elongation and subsequent secondary cell wall thickening. There was a major shift in abundance of transcripts for gene regulation, cell organization and metabolism between fiber elongation and fiber thickening that was fundamentally similar in both species. Each stage had its own distinctive features represented by specific metabolic and regulatory genes, a number of which have been noted previously. Many of the genes expressed in the fibers were of a similar type and developmental expression to those seen in other fiber-producing plants, indicating a conservation of mechanisms of cell elongation and wall thickening across diverse plant genera. Secondary metabolism and pectin synthesis and modification genes were amongst the most statistically significant differentially expressed categories between the two species during fiber elongation. The gene profiles of the fiber thickening stage, however, were almost identical between the two species, suggesting that their different final fiber quality properties may be established at earlier stages of fiber development. Expression levels of representative phenylpropanoid and pectin modification genes showed high correlations with specific fiber properties in an inter-specific cotton recombinant inbred line (RIL) population, supporting a role in determining fiber quality.

Total biosynthesis of hydrocortisone from a simple carbon source in yeast.

We report on the production of hydrocortisone, the major adrenal glucocorticoid of mammals and an important intermediate of steroidal drug synthesis, from a simple carbon source by recombinant Saccharomyces cerevisiae strains. An artificial and fully self-sufficient biosynthetic pathway involving 13 engineered genes was assembled and expressed in a single yeast strain. Endogenous sterol biosynthesis was rerouted to produce compatible sterols to serve as substrates for the heterologous part of the pathway. Biosynthesis involves eight mammalian proteins (mature forms of CYP11A1, adrenodoxin (ADX), and adrenodoxin reductase (ADR); mitochondrial forms of ADX and CYP11B1; 3beta-HSD, CYP17A1, and CYP21A1). Optimization involved modulating the two mitochondrial systems and disrupting of unwanted side reactions associated with ATF2, GCY1, and YPR1 gene products. Hydrocortisone was the major steroid produced. This work demonstrates the feasibility of transfering a complex biosynthetic pathway from higher eukaryotes into microorganisms.

The osmoprotectant glycine betaine inhibits salt-induced cross-tolerance towards lethal treatment in Enterococcus faecalis.

The response of Enterococcus faecalis ATCC 19433 to salt stress has been characterized previously in complex media. In this report, it has been demonstrated that this bacterium actively accumulates the osmoprotectant glycine betaine (GB) from salt-enriched complex medium BHI. To further understand the specific effects of GB and other osmoprotective compounds in salt adaptation and salt-induced cross-tolerance to lethal challenges, a chemically defined medium lacking putative osmoprotectants was used. In this medium, bacterial growth was significantly reduced by increasing concentrations of NaCl. At 0.75 M NaCl, 90% inhibition of the growth rate was observed; GB and its structural analogues restored growth to the non-salt-stressed level. In contrast, proline, pipecolate and ectoine did not allow growth recovery of stressed cells. Kinetic studies showed that the uptake of betaines shows strong structural specificity and occurs through a salt-stress-inducible high-affinity porter [Km = 3.3 microM; Vmax = 130 nmol min(-1) (mg protein)(-1); the uptake activity increased 400-fold in the presence of 0.5 M NaCl]. Moreover, GB and its analogues were accumulated as non-metabolizable cytosolic osmolytes and reached intracellular levels ranging from 1-3 to 1.5 micromol (mg protein)(-1). In contrast to the beneficial effect of GB on the growth of salt-stressed cultures of E. faecalis, its accumulation inhibits the salt-induced cross-tolerance to a heterologous lethal challenge. Indeed, pretreatment of bacterial cells with 0.5 M NaCl induced resistance to 0.3% bile salts (survival of adapted cells increased by a factor of 6800). The presence of GB in the adaptation medium reduced the acquisition of bile salts resistance 680-fold. The synthesis of 11 of the 13 proteins induced during salt adaptation was significantly reduced in the presence of GB. These results raise questions about the actual beneficial effect of GB in natural environments where bacteria are often subjected to various stresses.