Biology subjects

Warren, F. J.

Publications and source records attributed to Warren, F. J..

7 recordsLinked to original sources

bioRxiv2026

Wheat mutants lacking Starch Synthase 1 have altered starch composition and cell wall content

Starch Synthase 1 (SS1) participates in the synthesis of amylopectin. To determine its role in hexaploid bread wheat, we selected and combined TILLING mutations for each homoeologue to create two independent SS1-deficient lines. The lines, which have different combinations of ss1 mutations, both lacked SS1 protein. Both lines exhibited mild but significant changes to starch phenotype, including fewer short amylopectin chains, a slight increase in B-type starch granules and a modest increase in amylose content. Lack of SS1 also led to changes in the thermal properties of starch measured by differential scanning calorimetry including reduced enthalpy, and increased gelatinization temperature. Despite the changes to starch properties, the starch contents of the mutant lines compared to wild types were within the normal range, as were grain weight and protein content. However, the concentration of total- and water-extractable arabinoxylan, and MLG, were increased in white flour compared to wild-type controls. HighlightLack of SS1 led to changes in starch molecular structure and thermal behavior. Starch content and grain weight were normal but cell wall polysaccharides in white flour were increased.

plant biology↗

bioRxiv2025

Unearthing the rhizosphere microbiome recruited by ancestral bread wheat landraces

Crop root traits that modulate the soil microbiome can turn the tide of reduced fertility in intensively farmed land by optimising nutrient availability and resilience to environmental stresses. Advantageous genetic diversity that allows adaptation to nutrient availability is present in historic crop genotypes. The Watkins collection of bread wheat landraces is an unexploited resource, carrying untapped phenotypic traits. Here, we show that the rhizosphere microbiome assembly of these landraces is distinct compared to elite varieties, specifically those that come from ancestral groups (AGs) not used in modern breeding. We used 16S rRNA sequencing to identify changes in microbial communities of rhizosphere soil collected from 81 landraces and two elite varieties. We found high similarity in microbiome recruitment between the elite cultivars and the two AGs genetically closest to the elite. The rhizosphere microbiome of five AGs genetically distant from the elite cultivars showed significant differences in the abundance of taxa involved in nitrogen and carbon turnover, keystone taxa and associations within the microbial network. Our findings suggest that genes to recruit or suppress microbial taxa in the rhizosphere are shared by landraces from these AGs. Selective breeding for traits to control microbial functions can enhance soil productivity and crop performance.

ecology↗

bioRxiv2024

Novel amylase genes enable utilisation of resistant starch by bifidobacteria relevant to early-life microbiome development

Bifidobacterium species and strains are key members of the gut microbiota, appearing soon after birth and persisting into adulthood. Resistant starch is an important dietary substrate for adult-associated bifidobacteria, where its fermentation supports host health. However, little is known about how different starch structures interact with bifidobacteria across various ages and ecological niches. To address this, we carried out detailed growth kinetics screening of Bifidobacterium reference strains and unique isolates from breast-fed infants, testing their metabolic interaction with a variety of starch structures. 1H NMR metabolomics as well as analysis of CAZyme profiles from genomes were generated for each Bifidobacterium-starch combination. For a subset of resistant starch-utilising isolates, we integrated multi-omics approaches to attain further mechanistic interaction insights. Our results revealed that bifidobacterial starch hydrolysis capabilities are closely associated with their CAZyme profiles and appear to be connected to the niche they occupy. Notably, in one isolate of Bifidobacterium pseudolongum, we identified a novel gene cluster containing three multi-functional amylase enzymes complemented by several starch binding modules which were significantly upregulated in response to resistant starch. This gene cluster was also found in the genomes of bifidobacterial isolates from weaning infants and adults. These findings provide new insights into their participation in the maturation process of the infant gut microbiota. Uncovering mechanisms of metabolic interaction between starch structures and bifidobacteria underscores the importance of this ecological function and potential health implications.

microbiology↗

bioRxiv2022

Development of a high-throughput starch digestibility assay reveals wide variation among the A. E. Watkins wheat landrace collection

Breeding for less digestible starch in wheat can improve the health impact of bread and other wheat foods. Based on an established in vitro starch digestibility assay by Edwards et al. (2019) we developed a high-throughput assay to measure starch digestibility in hydrothermally processed samples for use in forward genetic approaches. Digestibility of purified starch from maize and wheat was measured using both methods and produced comparable results. Using the high-throughput assay, we estimated starch digestibility of 118 wheat landraces from the core Watkins collection and found wide variation across lines and elite UK varieties, (20% to 40% and 31% to 44% starch digested after 90 minutes respectively). Sieved flour fractions and purified starch for selected lines showed altered starch digestibility profiles compared with wholemeal flour, suggesting that matrix properties of flour rather than intrinsic properties of starch granules conferred the low starch digestibility observed.

biochemistry↗

bioRxiv2022

Contrasting roles of the wheat MRC in promoting starch granule initiation in leaves and repressing the onset of B-type granule initiation in the endosperm

The spatial and temporal patterns by which starch granules initiate vary greatly between species and organs, but molecular factors that contribute to these diverse patterns are poorly understood. We reveal distinct organ-specific roles of the MYOSIN-RESEMBLING CHLOROPLAST PROTEIN (MRC) in regulating granule initiation in the endosperm and leaves of wheat. We isolated three independent TILLING mutants of tetraploid wheat (Triticum turgidum cv. Kronos) with premature stop or missense mutations in the A-genome homeolog, which we showed to be the only active homeolog in tetraploid wheat due to a disruption of the B-genome homeolog. Wheat endosperm contains both large A-type granules initiated during early grain development, and small B-type granules that initiate about 10 - 15 days later. The mrc mutants had significantly smaller A-type granules and a higher relative volume of B-type granules in the endosperm than the wild type. Whereas B-type granules initiated 15 - 20 days post anthesis (dpa) in the wild-type, they appeared as early as 10 dpa in the mrc-1 mutant, suggesting a role for MRC in suppressing B-type granule initiation during early grain development. By contrast, MRC promotes granule initiation in leaves: mutants carrying premature stop mutations in MRC had fewer granules per chloroplast than the wild type. These contrasting roles of MRC among wheat organs provide new insight into functional diversification of granule initiation proteins, and suggest that they may facilitate the diverse patterns of granule initiation observed across species and organs.

plant biology↗

bioRxiv2022

The impact of the soluble protein fraction and kernel hardness on wheat flour starch digestibility

Wheat is the staple crop for 35% of the worlds population, providing a major source of calories for much of the worlds population. Starch is the main source of energy in wheat flour, but the digestibility of wheat starch varies greatly between different flours and wheat products. This has relevance from a health perspective because wheat starch products that are rapidly digested and elicit large post-prandial glucose peaks are associated with a host of cardiac and metabolic disorders. In this study, we investigate the impact of protein on starch digestion in three commercially sourced flours with different grain hardness. Grain hardness impacted on flour particle size, but not significantly on starch digestion. A soluble extract of wheat proteins was found to dramatically reduce starch digestion, even following gastric proteolysis. Proteomic analysis revealed that this soluble extract was enriched in proteinaceous -amylase inhibitors which were partially degraded during gastric proteolysis. Therefore, we conclude that the soluble proteins of wheat flour have a significant contribution towards retarding starch digestion, even following gastric digestion.

biochemistry↗

bioRxiv2021

STARCH SYNTHASE 4 is required for normal starch granule initiation in amyloplasts of wheat endosperm

O_LIStarch granule initiation is poorly understood at the molecular level. The glucosyltransferase, STARCH SYNTHASE 4 (SS4), plays a central role in granule initiation in Arabidopsis leaves, but its function in cereal endosperms is unknown. We investigated the role of SS4 in wheat, which has a distinct spatiotemporal pattern of granule initiation during grain development. C_LIO_LIWe generated TILLING mutants in tetraploid wheat (Triticum turgidum) that are defective in both SS4 homoeologs. The morphology of endosperm starch was examined in developing and mature grains. C_LIO_LISS4 deficiency led to severe alterations in endosperm starch granule morphology. During early grain development, while the wild type initiated single A-type granules per amyloplast, most amyloplasts in the mutant formed compound granules due to multiple initiations. This phenotype was similar to mutants deficient in B-GRANULE CONTENT 1 (BGC1). SS4 deficiency also reduced starch content in leaves and pollen grains. C_LIO_LIWe propose that SS4 and BGC1 are required for the proper control of granule initiation during early grain development that leads to a single A-type granule per amyloplast. The absence of either protein results in a variable number of initiations per amyloplast and compound granule formation. C_LI

plant biology↗