New Growth-Related Features of Wheat Grain Pericarp Revealed by Synchrotron-Based X-ray Micro-Tomography and 3D Reconstruction.

Wheat ( L.) is one of the most important crops as it provides 20% of calories and proteins to the human population. To overcome the increasing demand in wheat grain production, there is a need for a higher grain yield, and this can be achieved in particular through an increase in the grain weight.

Spatial correlation of water distribution and fine structure of arabinoxylans in the developing wheat grain.

This study was to investigate the distribution of water and arabinoxylan structures in growing wheat grain using two complementary imaging techniques, magnetic resonance microimaging (μMRI) and mass spectrometry imaging (MSI). μMRI showed an inhomogeneous water distribution, particularly at early stages. This heterogeneity revealed histological differences that corresponded, within the limits of resolution of μMRI, to tissues with specific physiological functions, including the vascular bundles, the cavity and the endosperm periphery.

The endosperm cavity of wheat grains contains a highly hydrated gel of arabinoxylan.

Cereal grains provide a substantial part of the calories for humans and animals. The main quality determinants of grains are polysaccharides (mainly starch but also dietary fibers such as arabinoxylans, mixed-linkage glucans) and proteins synthesized and accumulated during grain development in a specialized storage tissue: the endosperm. In this study, the composition of a structure localized at the interface of the vascular tissues of the maternal plant and the seed endosperm was investigated.

The TaCslA12 gene expressed in the wheat grain endosperm synthesizes wheat-like mannan when expressed in yeast and Arabidopsis.

Mannan is a class of cell wall polysaccharides widespread in the plant kingdom. Mannan structure and properties vary according to species and organ. The cell walls of cereal grains have been extensively studied due to their role in cereal processing and to their beneficial effect on human health as dietary fiber.

Challenging the putative structure of mannan in wheat (Triticum aestivum) endosperm.

In wheat endosperm, mannan, is poorly documented. Nevertheless, this hemicellulosic polysaccharide might have a determinant role in wheat grain development since, in Arabidopsis thaliana, mutants with a reduced amount of mannan show an altered seed development. In order to gain knowledge about mannan in wheat, we have determined its biochemical structure in wheat endosperm where mannose content is about 0.

Use of X-ray micro computed tomography imaging to analyze the morphology of wheat grain through its development.

Background: Wheat is one of the most important staple source in the world for human consumption, animal feed and industrial raw materials. To deal with the global and increasing population demand, enhancing crop yield by increasing the final weight of individual grain is considered as a feasible solution. Morphometric analysis of wheat grain plays an important role in tracking and understanding developmental processes by assessing potential impacts on grains properties, size and shape that are major determinants of final grain weight.

Multi-excitation hyperspectral autofluorescence imaging for the exploration of biological samples.

Many plant tissues can be observed thanks to autofluorescence of their cell wall components. Hyperspectral autofluorescence imaging using confocal microscopy is a fast and efficient way of mapping fluorescent compounds in samples with a high spatial resolution. However a huge spectral overlap is observed between molecular species.

Ferulate and lignin cross-links increase in cell walls of wheat grain outer layers during late development.

Important biological, nutritional and technological roles are attributed to cell wall polymers from cereal grains. The composition of cell walls in dry wheat grain has been well studied, however less is known about cell wall deposition and modification in the grain outer layers during grain development. In this study, the composition of cell walls in the outer layers of the wheat grain (Triticum aestivum Recital cultivar) was investigated during grain development, with a focus on cell wall phenolics.

Developing Pericarp of Maize: A Model to Study Arabinoxylan Synthesis and Feruloylation.

Cell walls are comprised of networks of entangled polymers that differ considerably between species, tissues and developmental stages. The cell walls of grasses, a family that encompasses major crops, contain specific polysaccharide structures such as xylans substituted with feruloylated arabinose residues. Ferulic acid is involved in the grass cell wall assembly by mediating linkages between xylan chains and between xylans and lignins.

Breeding maize for silage and biofuel production, an illustration of a step forward with the genome sequence.

The knowledge of the gene families mostly impacting cell wall digestibility variations would significantly increase the efficiency of marker-assisted selection when breeding maize and grass varieties with improved silage feeding value and/or with better straw fermentability into alcohol or methane. The maize genome sequence of the B73 inbred line was released at the end of 2009, opening up new avenues to identify the genetic determinants of quantitative traits. Colocalizations between a large set of candidate genes putatively involved in secondary cell wall assembly and QTLs for cell wall digestibility (IVNDFD) were then investigated, considering physical positions of both genes and QTLs.

Mutation in Brachypodium caffeic acid O-methyltransferase 6 alters stem and grain lignins and improves straw saccharification without deteriorating grain quality.

Cereal crop by-products are a promising source of renewable raw material for the production of biofuel from lignocellulose. However, their enzymatic conversion to fermentable sugars is detrimentally affected by lignins. Here the characterization of the Brachypodium Bd5139 mutant provided with a single nucleotide mutation in the caffeic acid O-methyltransferase BdCOMT6 gene is reported.

Proteome evolution of wheat (Triticum aestivum L.) aleurone layer at fifteen stages of grain development.

Unlabelled: The aleurone layer (AL) is the grain peripheral tissue; it is rich in micronutrients, vitamins, antioxidants, and essential amino acids. This highly nutritive part of the grain has been less studied partly because its isolation is so laborious. In the present study, the ALs of Triticum aestivum (variety Récital) were separated manually at 15 stages of grain development.

Endomembrane proteomics reveals putative enzymes involved in cell wall metabolism in wheat grain outer layers.

Cereal grain outer layers fulfil essential functions for the developing seed such as supplying energy and providing protection. In the food industry, the grain outer layers called 'the bran' is valuable since it is rich in dietary fibre and other beneficial nutriments. The outer layers comprise several tissues with a high content in cell wall material.

The wheat grain contains pectic domains exhibiting specific spatial and development-associated distribution.

Cell walls are complex structures surrounding plant cells with a composition that varies among species and even within a species between organs, cell types and development stages. For years, cell walls in wheat grains were described as simple walls consisting mostly of arabinoxylans and mixed-linked beta glucans. Proteomic and transcriptomic studies identified enzyme families involved in the synthesis of many more cell wall polysaccharides in the wheat grains.

Characterization of the tomato ARF gene family uncovers a multi-levels post-transcriptional regulation including alternative splicing.

Background: The phytohormone auxin is involved in a wide range of developmental processes and auxin signaling is known to modulate the expression of target genes via two types of transcriptional regulators, namely, Aux/IAA and Auxin Response Factors (ARF). ARFs play a major role in transcriptional activation or repression through direct binding to the promoter of auxin-responsive genes. The present study aims at gaining better insight on distinctive structural and functional features among ARF proteins.

The E domains of pentatricopeptide repeat proteins from different organelles are not functionally equivalent for RNA editing.

RNA editing in plants is an essential post-transcriptional process that modifies the genetic information encoded in organelle genomes. Forward and reverse genetics approaches have revealed the prevalent role of pentatricopeptide repeat (PPR) proteins in editing in both plastids and mitochondria, confirming the shared origin of this process in both organelles. The E domain at or near the C terminus of these proteins has been shown to be essential for editing, and is presumed to recruit the enzyme that deaminates the target cytidine residue.

Organellar RNA editing.

RNA editing is a term used for a number of mechanistically different processes that alter the nucleotide sequence of RNA molecules to differ from the gene sequence. RNA editing occurs in a wide variety of organisms and is particularly frequent in organelle transcripts of eukaryotes. The discontiguous phylogenetic distribution of mRNA editing, the mechanistic differences observed in different organisms, and the nonhomologous editing machinery described in different taxonomic groups all suggest that RNA editing has appeared independently several times.

OTP70 is a pentatricopeptide repeat protein of the E subgroup involved in splicing of the plastid transcript rpoC1.

Over 20 proteins of the pentatricopeptide repeat (PPR) family have been demonstrated to be involved in RNA editing in plant mitochondria and chloroplasts. All of these editing factors contain a so-called 'E' domain that has been shown to be essential for editing to occur. The presumption has been that this domain recruits the (unknown) editing enzyme to the RNA.

Plant RNA editing.

In plants, post-transcriptional modification of transcripts includes C-to-U, U-to-C and A-to-I editing. RNA editing in plants is essential, with many mutants impaired in editing of specific sites exhibiting strong deleterious phenotypes, even lethality. The majority of editing in plants occurs in mitochondrial and plastid transcripts, however, A-to-I editing also occurs in cytosolic tRNAs.

A study of new Arabidopsis chloroplast RNA editing mutants reveals general features of editing factors and their target sites.

RNA editing in higher plant organelles results in the conversion of specific cytidine residues to uridine residues in RNA. The recognition of a specific target C site by the editing machinery involves trans-acting factors that bind to the RNA upstream of the C to be edited. In the last few years, analysis of mutants affected in chloroplast biogenesis has identified several pentatricopeptide repeat (PPR) proteins from the PLS subfamily that are essential for the editing of particular RNA transcripts.

Pentatricopeptide repeat proteins with the DYW motif have distinct molecular functions in RNA editing and RNA cleavage in Arabidopsis chloroplasts.

The plant-specific DYW subclass of pentatricopeptide repeat proteins has been postulated to be involved in RNA editing of organelle transcripts. We discovered that the DYW proteins CHLORORESPIRATORY REDUCTION22 (CRR22) and CRR28 are required for editing of multiple plastid transcripts but that their DYW motifs are dispensable for editing activity in vivo. Replacement of the DYW motifs of CRR22 and CRR28 by that of CRR2, which has been shown to be capable of endonucleolytic cleavage, blocks the editing activity of both proteins.

The Arabidopsis gene YS1 encoding a DYW protein is required for editing of rpoB transcripts and the rapid development of chloroplasts during early growth.

Virescence, a phenotype in which leaves green more slowly than usual, is recognized to play a role in protection from photo-oxidative damage before healthy chloroplasts are developed. The elucidation of the molecular mechanisms underlying virescence will provide insights into how the development of chloroplasts is controlled. In this study, we find that knockout alleles of Yellow Seedlings 1 (YS1) in Arabidopsis lead to a virescent phenotype, which disappears by 3 weeks after germination.

CLB19, a pentatricopeptide repeat protein required for editing of rpoA and clpP chloroplast transcripts.

RNA editing changes the sequence of many transcripts in plant organelles, but little is known about the molecular mechanisms determining the specificity of the process. In this study, we have characterized CLB19 (also known as PDE247), a gene that is required for editing of two distinct chloroplast transcripts, rpoA and clpP. Loss-of-function clb19 mutants present a yellow phenotype with impaired chloroplast development and early seedling lethality under greenhouse conditions.

A rapid high-throughput method for the detection and quantification of RNA editing based on high-resolution melting of amplicons.

We describe a rapid, high-throughput method to scan for new RNA editing sites. This method is adapted from high-resolution melting (HRM) analysis of amplicons, a technique used in clinical research to detect mutations in genomes. The assay was validated by the discovery of six new editing sites in different chloroplast transcripts of Arabidopsis thaliana.

Ecotype allelic variation in C-to-U editing extent of a mitochondrial transcript identifies RNA-editing quantitative trait loci in Arabidopsis.

In higher plants, RNA editing is a posttranscriptional process that converts C to U in organelle mRNAs. Although RNA editing in mitochondria occurs much more frequently than in chloroplasts, editing of exogenously supplied RNA substrates in vitro and in organello has shown that editing in the two organelles shares some common features. In particular, the 20 nucleotides upstream of the editing site play an important role in specifying the C to be edited.