Biology subjects

Connorton, J. M.

Publications and source records attributed to Connorton, J. M..

4 recordsLinked to original sources

bioRxiv2022

A two-gene strategy increases the iron and zinc concentration of wheat flour and improves mineral bioaccesibility for human nutrition.

Dietary deficiencies of iron and zinc cause human malnutrition globally, which can be mitigated by biofortified staple crops. Conventional breeding approaches to increase grain mineral concentrations in wheat (Triticum aestivum L.) have had only limited success so far due to relatively low genetic variation. Here we demonstrate that a transgenic approach combining endosperm-specific expression of the wheat vacuolar iron transporter gene TaVIT2-D with constitutive expression of the rice nicotianamine synthase gene OsNAS2 has the potential to dramatically improve mineral micronutrient intake from wheat products. In two distinct bread wheat cultivars, we show that the VIT-NAS construct led to a two-fold increase in zinc to [~]50 {micro}g g-1 in wholemeal flour and a two-fold increase in both zinc and iron in hand-milled white flour. In highly pure, roller-milled white flour, the concentration of iron was enhanced three-fold to [~]25 {micro}g g-1. A greater than three-fold increase in the level of the natural plant metal chelator nicotianamine in the grain of VIT-NAS lines was associated with improved iron and zinc bioaccessibility in white flour. The growth of VIT-NAS plants in the greenhouse was indistinguishable from untransformed controls. We conclude that the effects of each gene cassette are additive in altering the total concentration and distribution of iron and zinc in wheat grains. This demonstrates the potential of a transgenic approach to enhance the nutritional quality of wheat well beyond what is possible by breeding approaches in order to alleviate dietary mineral deficiencies.

plant biology↗

bioRxiv2021

Subcellular dynamics studies reveal how tissue-specific distribution patterns of iron are established in developing wheat grains

Understanding iron trafficking in plants is key to enhancing the nutritional quality of crops. Due to the difficulty of imaging iron in transit, little is known about iron translocation and distribution in developing seeds. A novel approach, combining 57Fe isotope labelling and NanoSIMS, was used to visualize iron translocation dynamics at the subcellular level in wheat grain, Triticum aestivum L. We were able to track the main route of iron from maternal tissues to the embryo through different cell types. Further evidence for this route was provided by genetically diverting iron into storage vacuoles, as confirmed by histological staining and TEM-EDS. Virtually all iron was found in intracellular bodies, indicating symplastic rather than apoplastic transport. Aleurone cells contained a new type of iron body, highly enriched in 57Fe, and most likely represents iron-nicotianamine being delivered to phytate globoids. Correlation with tissue-specific gene expression provides an updated model of iron homeostasis in cereal grains with relevance for future biofortification efforts.

plant biology↗

bioRxiv2017

BRUTUS-LIKE proteins moderate the transcriptional response to iron deficiency in roots

Iron is an essential micronutrient but in excess is toxic inside cells. Under iron deficiency, the expression of iron uptake genes is increased, but it is not known how the transcriptional response is controlled to avoid uptake of too much iron. The hemerythrin E3 ligases BRUTUS (BTS) and BTS-LIKE (BTSL) have previously been identified as negative regulators of the iron deficiency response. Our phylogenetic analysis indicated that BTSL proteins are present in dicotyledonous plants only and form a separate clade from BTS homologs. BTSL1 and BTSL2 in Arabidopsis thaliana are in a network with nearly all iron uptake genes, whereas BTS is in a shoot-specific network. BTSL1 and BTSL2 are expressed predominantly in the root epidermis and cortex, separate from BTS in the root stele, shoot and embryos. Mutant analysis identified BTSL2 as the dominant paralog of the otherwise redundant BTSL genes. The btsl double mutant had increased protein levels of FIT, the FER-like Iron deficiency-induced Transcription factor, and failed to switch off the transcriptional response upon iron resupply, leading to dramatic iron accumulation in roots and shoots. Protein interaction between the C-terminus of BTSL proteins and FIT indicate that FIT is a direct target for degradation. Taken together, our studies show that BTSL1 and BTSL2 control iron uptake in the epidermis and cortex, upstream of BTS in the vasculature and leaves.

plant biology↗

bioRxiv2017

Altering Expression Of A Vacuolar Iron Transporter Doubles Iron Content In White Wheat Flour

Iron deficiency anaemia is a major global health issue, which has prompted mandatory fortification of cereal products with iron salts or elemental iron in many countries around the world. Rather than post-harvest fortification, biofortification - increasing the intrinsic nutritional quality of crops - is a more sustainable way of alleviating nutrient deficiencies. To identify target genes for biofortification of wheat (Triticum aestivum), we functionally characterized homologues of the Vacuolar Iron Transporter (VIT). The wheat genome contains two VIT paralogues, TaVIT1 and TaVIT2, which have different expression patterns, but are both low in the endosperm. TaVIT2, but not TaVIT1, was able to transport iron in a yeast complementation assay. TaVIT2 also transported manganese but not zinc. By over-expressing TaVIT2 under the control of an endosperm-specific promoter, we achieved a 2-fold increase in iron in white flour fractions, exceeding minimum UK legal fortification levels. The highiron trait was consistent across independent lines and was stable in the next generation and in two different growth conditions. The single-gene approach impacted minimally on plant growth and was also effective in barley. The anti-nutrient phytate was not increased in white flour from the cisgenic wheat lines, suggesting that food products made from it could contribute to improved iron nutrition.

plant biology↗