In Triticeae endosperm (e.g. wheat and barley), starch granules have a bimodal size distribution (with A- and B-type granules) whereas in other grasses the endosperm contains starch granules with a unimodal size distribution. Here, we identify the gene, BGC1 (B-GRANULE CONTENT 1), responsible for B-type starch granule content in Aegilops and wheat. Orthologues of this gene are known to influence starch synthesis in diploids such as rice, Arabidopsis, and barley. However, using polyploid Triticeae species, we uncovered a more complex biological role for BGC1 in starch granule initiation: BGC1 represses the initiation of A-granules in early grain development but promotes the initiation of B-granules in mid grain development. We provide evidence that the influence of BGC1 on starch synthesis is dose dependent and show that three very different starch phenotypes are conditioned by the gene dose of BGC1 in polyploid wheat: normal bimodal starch granule morphology; A-granules with few or no B-granules; or polymorphous starch with few normal A- or B-granules. We conclude from this work that BGC1 participates in controlling B-type starch granule initiation in Triticeae endosperm and that its precise effect on granule size and number varies with gene dose and stage of development.

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Tel +44 (0)1223 34249. 23 24 Keywords: high lysine, PBF, large embryo, shrunken endosperm.  Wheat and barley LYS3/PBF mutants have enlarged embryos suggesting that this gene 40 suppresses embryo growth. 41  The down-stream target genes of PBF in wheat are predicted to be involved in a wide 42 range of biological processes including organ development and starch metabolism. 43 3 ABSTRACT 44 Mutations at the LYS3 locus in barley have multiple effects on grain development, including 45 an increase in embryo size and a decrease in endosperm starch content. The gene underlying 46 LYS3 was identified by genetic mapping and mutations in this gene were identified in all four 47 6 2. Materials and methods 102 2.1. Barley germplasm 103 Grains of Bomi, Morex and Risø1508 were obtained from the Germplasm Resources Unit, 104 John Innes Centre, Norwich, UK and Risø18, Risø19, M1460 and Minerva were kindly 105 supplied by Birthe Møller Jespersen, University of Copenhagen, Denmark. 106 107 2.2. Plant growth 108For mapping experiments, individual grains were germinated in Petri dishes on moist filter 109 paper. After over-night incubation at 4 C, plates were transferred to room temperature. 110When roots and shoots were established, each seedling was transplanted into a 1 L pot 111containing Levington M2 compost (Scotts Professional, Ipswich, UK) and grown in a 112 glasshouse. In winter, additional lighting was provided by sodium lamps for 16 h per day and 113 temperatures were maintained between 15 C (night) and 20 °C (day). In summer, plants 114were grown in a glasshouse under ambient conditions. 115Wheat TILLING mutants were sown directly into M2 compost, incubated at 4 C for 3 116 days and then transferred to a glasshouse with a 22-hour photoperiod and temperatures of 21 117 C (night) and 18 C (day). Supplementary lighting was provided by a mixture of high-118pressure sodium lamps and both far red and white LED lights (Conviron, Winnipeg, US). 119 120 Analysis of grain and embryo development 121Anthesis occurred whilst the ear was enveloped in the flag leaf so the exact day of anthesis 122 was difficult to determine without damaging the developing spike. Accordingly, flowering 123 time was defined as the day on which the awns of the developing ear protruded more than 1 124 cm above the leaf sheath and grain/embryo age was measured in days after flowering (DAF). 125

The weak acid sorbic acid is a common preservative used in soft drink beverages to control microbial spoilage. Consumers and industry are increasingly transitioning to low-sugar food formulations, but potential impacts of reduced-sugar on preservative efficacy are barely characterised. In this study, we report enhanced sorbic acid resistance of spoilage yeasts in low-glucose conditions. We had anticipated that low glucose may induce respiratory metabolism, previously shown to be targeted by sorbic acid. However, a shift from respiratory to fermentative metabolism was correlated with the sorbic acid resistance in low glucose. Fermentation-deficient yeast species did not show the low-glucose resistance phenotype. Phenotypes observed for certain yeast deletion strains suggested roles for glucose signalling and repression pathways in the sorbic acid resistance at low glucose. This low-glucose induced sorbic acid resistance was alleviated by supplementing yeast cultures with succinic acid, a metabolic intermediate of respiratory metabolism (and a food-safe additive) that promoted respiration. The results indicate that metabolic adaptation of spoilage yeasts promotes sorbic acid resistance at low glucose, providing new insight into potential spoilage, and preservation, of foodstuffs as both food producers and consumers move towards a reduced-sugar landscape.

Previously, we identified a quantitative trait locus on the group 4 chromosomes of Aegilops and bread wheat that controls B-type starch-granule content. Here, we identify a candidate gene by fine-mapping in Aegilops and confirm its function using wheat TILLING mutants. This gene is orthologous to the FLOURY ENDOSPERM 6 (FLO6) gene of rice and barley and the PTST2 gene of Arabidopsis. In Triticeae endosperm, reduction in the gene dose of functional FLO6 alleles results in reduction, or loss, of B-granules. This is due to repression of granule initiation in lategrain development, but has no deleterious impact on the synthesis of A-granules.The complete absence of functional FLO6, however, results in reduced numbers of normal A-type and B-type granules and the production of highly-abnormal granules that vary in size and shape. This polymorphous starch seen in a wheat flo6 triple mutant is similar to that observed in the barley mutant Franubet. Analysis of Franubet (fractured Nubet) starch suggests that the mutant A-granules are not fractured but compound, due to stimulation of granule initiation in plastids during early-grain development. Thus, in different situations in Triticeae, FLO6 either stimulates or represses granule initiation.