A SQUAMOSA MADS-box gene involved in the regulation of anthocyanin accumulation in bilberry fruits

Anthocyanins are important health promoting phytochemicals that are abundant in many fleshy fruits. Bilberry (Vaccinium myrtillus L.) is one of the best sources of these compounds. Here we report on the expression pattern and functional analysis of a SQUAMOSA (SQUA) class MADS-box transcription factor, VmTDR4, associated with anthocyanin biosynthesis in bilberry. Levels of VmTDR4 expression were spatially and temporally linked with colour development and anthocyanin-related gene expression. Virus induced gene silencing (VIGS) was used to suppress VmTDR4 expression in bilberry resulting in substantial reduction in anthocyanin levels in fully ripe fruits. Chalcone synthase was used a positive control in the VIGS experiments. Additionally, in sectors of fruit tissue in which the expression of the VmTDR4 gene was silenced, the expression of R2R3 MYB family transcription factors related to the biosynthesis of flavonoids were also altered. We conclude that VmTDR4 plays an important role in the accumulation of anthocyanins during normal ripening in bilberry; probably through direct or indirect control of transcription factors belonging to the R2R3 MYB family

The contribution of fibre components to water absorption of wheat grown in the UK

Background and objectives The water absorption (WA) of white wheat flour is a major factor affecting processing quality, and millers, therefore, process their wheat to achieve the required level. Although it is likely that WA is determined by the amounts and compositions of three major grain components, starch, protein, and arabinoxylan, the contribution of the latter is not agreed and not recognized in the widely used Farrand equation. Findings We have measured a range of parameters related to fiber amount and composition and tested the ability of these to improve the prediction of WA using a modified Farrand equation. The addition of a range of single fiber traits improved the prediction of WA from a baseline of 82.98% to a maximum of 86.78%, but inclusion of all fiber traits as PCs resulted in a further improvement to 90%. Inclusion of the PCs also accounted for variation in WA between harvest years. The greatest improvement from inclusion of a single trait was observed with β‐glucan, the inclusion of arabinogalactan peptide (AGP) also resulted in improved prediction of WA. Conclusions The study shows that fiber components contribute to variation in WA, including differences between harvest years, but that β‐glucan and AGP have similar or greater impacts than AX. Significance and novelty The study dissects the contributions of AX amount and composition to WA and demonstrates a contribution of b‐glucan for the first time

Genetic improvement of tomato by targeted control of fruit softening

Controlling the rate of softening to extend shelf life was a key target for researchers engineering genetically modified (GM) tomatoes in the 1990s, but only modest improvements were achieved. Hybrids grown nowadays contain 'non-ripening mutations' that slow ripening and improve shelf life, but adversely affect flavor and color. We report substantial, targeted control of tomato softening, without affecting other aspects of ripening, by silencing a gene encoding a pectate lyase

Pericarp tissue microstructure and cell wall polysaccharide chemistry are differently affected in lines of tomato with contrasted firmness

International audienceThe contribution of tissue histology and cell wall polysaccharides chemistry to describing ripe tomato fruit texture was addressed in near isogenic lines of fruits harboring firmness QTL. These lines were constructed in Levovil (L), VilB (B), M82 (P) and Moneyberg (Mbg) genetic backgrounds and carried introgressed fragments from three origins on chromosomes 2, 3, 4, 5 or 9 (and two sub-regions a and b). The firmness of their pericarp tissue was measured by compression testing and related to cell size distribution and to published data on their cell wall polysaccharide chemistry. The pericarp tissue from all L9 lines, B9 and P3.4 was firmer than the respective parental line while that from Mbg9 and P9.2.5 was softer. The pericarp tissue from L4, L4a and Mbg5 fruit was made of larger cells while that from Mbg2 and Mbg9 had smaller cells than their parents. Correlations were found between firmness and cell size distribution for QTLs only in the Levovil group. Correlations between firmness, histological characteristics and cell wall polysaccharide chemistry indicate positive relations between glucose-containing polysaccharide (cellulose and hemicelluloses) contents and pericarp tissue thickness. Other positive relations were found between galactosylated pectins and hemicelluloses and firmness in QTL lines of the Levovil background. The results show that chromosomes 9, 5, 4 and 2 are associated with pericarp histology in these lines and that pericarp tissue firmness depends on histology and cell wall chemistry according to genetics. These tomato lines represent good models to study the complex contributions of turgor pressure, cell wall chemistry, tissue architecture and their mechanisms of modulation underpinning texture in ripening tomatoes

Near isogenic lines of tomato for texture contrasted QTL showed altered pericarp histology and cell wall chemistry

International audienc

Genetics and epigenetics of fruit development and ripening

Fruits come in a vast variety of forms with both dry and fleshy types being essential components of the human diet. Elegant studies on the dry fruits of Arabidopsis have identified a suite of transcription factors involved in their development and dehiscence. Recent discoveries in tomato have revealed a hitherto unsuspected regulatory network involved in the developmental regulation of ripening in these fleshy fruits. Intriguingly it has become apparent that tomato shares some elements of its regulatory network in common with those involved in fruit development in Arabidopsis. Furthermore epigenetic variation has been shown to influence tomato ripening. These discoveries are likely to have a major impact on strategies for crop improvement in fruit bearing species

Genetic variation in wheat grain quality is associated with differences in the galactolipid content of flour and the gas bubble properties of dough liquor

Lipids affect the quality of wheat flour for breadmaking. One possible mechanism is stabilization of the gas cells which are formed during dough mixing and expanded during fermentation, leading to a greater loaf volume and evenness of texture. We therefore compared the lipidomic profiles of flour and dough liquor fractions (which contain surface-active components present at the gas bubble interface) from two sets of wheat lines differing in allelic variation at a QTL for loaf volume. Analyses of fractions from three field trials showed consistent increases in the contents of galactolipids (monogalactosyl diglyceride and digalactosyl diglyceride) in flour and dough liquor of the lines with the increasing (good quality) allele. Biophysical analysis showed that this was associated with greater elasticity of the dough liquor fraction. This is consistent with published studies reporting a relationship between galactolipids and breadmaking quality and suggests a mechanism of action for the QTL

A Naturally Occurring Epigenetic Mutation in a Gene Encoding an SBP-box Transcription Factor Inhibits Tomato Fruit Ripening

A major component in the regulatory network controlling fruit ripening is likely to be the gene at the tomato Colorless non-ripening (Cnr) locus1, 2. The Cnr mutation results in colorless fruits with a substantial loss of cell-to-cell adhesion. The nature of the mutation and the identity of the Cnr gene were previously unknown. Using positional cloning and virus-induced gene silencing, here we demonstrate that an SBP-box (SQUAMOSA promoter binding protein–like) gene resides at the Cnr locus. Furthermore, the Cnr phenotype results from a spontaneous epigenetic change in the SBP-box promoter. The discovery that Cnr is an epimutation was unexpected, as very few spontaneous epimutations have been described in plants3, 4. This study demonstrates that an SBP-box gene is critical for normal ripening and highlights the likely importance of epialleles in plant development and the generation of natural variation