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Fulltext Extensive Genetic Variation at the Sr22 Wheat Stem Rust Resistance Gene Locus in the Grasses Revealed Through Evolutionary Genomics and Functional Analyses

Md Hatta MA, Ghosh S, Athiyannan N, Richardson T, Steuernagel B, Yu G, et al.

Mol Plant Microbe Interact, 2020 Nov;33(11):1286-1298.
PMID: 32779520 DOI: 10.1094/MPMI-01-20-0018-R

In the last 20 years, severe wheat stem rust outbreaks have been recorded in Africa, Europe, and Central Asia. This previously well controlled disease, caused by the fungus Puccinia graminis f. sp. tritici, has reemerged as a major threat to wheat cultivation. The stem rust (Sr) resistance gene Sr22 encodes a nucleotide-binding and leucine-rich repeat receptor which confers resistance to the highly virulent African stem rust isolate Ug99. Here, we show that the Sr22 gene is conserved among grasses in the Triticeae and Poeae lineages. Triticeae species contain syntenic loci with single-copy orthologs of Sr22 on chromosome 7, except Hordeum vulgare, which has experienced major expansions and rearrangements at the locus. We also describe 14 Sr22 sequence variants obtained from both Triticum boeoticum and the domesticated form of this species, T. monococcum, which have been postulated to encode both functional and nonfunctional Sr22 alleles. The nucleotide sequence analysis of these alleles identified historical sequence exchange resulting from recombination or gene conversion, including breakpoints within codons, which expanded the coding potential at these positions by introduction of nonsynonymous substitutions. Three Sr22 alleles were transformed into wheat cultivar Fielder and two postulated resistant alleles from Schomburgk (hexaploid wheat introgressed with T. boeoticum segment carrying Sr22) and T. monococcum accession PI190945, respectively, conferred resistance to P. graminis f. sp. tritici race TTKSK, thereby unequivocally confirming Sr22 effectiveness against Ug99. The third allele from accession PI573523, previously believed to confer susceptibility, was confirmed as nonfunctional against Australian P. graminis f. sp. tritici race 98-1,2,3,5,6.[Formula: see text] Copyright © 2020 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.
Rapid cloning of disease-resistance genes in plants using mutagenesis and sequence capture

Steuernagel B, Periyannan SK, Hernández-Pinzón I, Witek K, Rouse MN, Yu G, et al.

Nat Biotechnol, 2016 Jun;34(6):652-5.
PMID: 27111722 DOI: 10.1038/nbt.3543

Wild relatives of domesticated crop species harbor multiple, diverse, disease resistance (R) genes that could be used to engineer sustainable disease control. However, breeding R genes into crop lines often requires long breeding timelines of 5-15 years to break linkage between R genes and deleterious alleles (linkage drag). Further, when R genes are bred one at a time into crop lines, the protection that they confer is often overcome within a few seasons by pathogen evolution. If several cloned R genes were available, it would be possible to pyramid R genes in a crop, which might provide more durable resistance. We describe a three-step method (MutRenSeq)-that combines chemical mutagenesis with exome capture and sequencing for rapid R gene cloning. We applied MutRenSeq to clone stem rust resistance genes Sr22 and Sr45 from hexaploid bread wheat. MutRenSeq can be applied to other commercially relevant crops and their relatives, including, for example, pea, bean, barley, oat, rye, rice and maize.
Fulltext The wheat Sr22, Sr33, Sr35 and Sr45 genes confer resistance against stem rust in barley

Hatta MAM, Arora S, Ghosh S, Matny O, Smedley MA, Yu G, et al.

Plant Biotechnol J, 2021 Feb;19(2):273-284.
PMID: 32744350 DOI: 10.1111/pbi.13460

In the last 20 years, stem rust caused by the fungus Puccinia graminis f. sp. tritici (Pgt), has re-emerged as a major threat to wheat and barley production in Africa and Europe. In contrast to wheat with 60 designated stem rust (Sr) resistance genes, barley's genetic variation for stem rust resistance is very narrow with only ten resistance genes genetically identified. Of these, only one complex locus consisting of three genes is effective against TTKSK, a widely virulent Pgt race of the Ug99 tribe which emerged in Uganda in 1999 and has since spread to much of East Africa and parts of the Middle East. The objective of this study was to assess the functionality, in barley, of cloned wheat Sr genes effective against race TTKSK. Sr22, Sr33, Sr35 and Sr45 were transformed into barley cv. Golden Promise using Agrobacterium-mediated transformation. All four genes were found to confer effective stem rust resistance. The barley transgenics remained susceptible to the barley leaf rust pathogen Puccinia hordei, indicating that the resistance conferred by these wheat Sr genes was specific for Pgt. Furthermore, these transgenic plants did not display significant adverse agronomic effects in the absence of disease. Cloned Sr genes from wheat are therefore a potential source of resistance against wheat stem rust in barley.
Prostaglandin F2-Alpha Eye Drops (Bimatoprost) in Graves' Orbitopathy: A Randomized Controlled Double-Masked Crossover Trial (BIMA Trial)

Draman MS, Morris DS, Evans S, Haridas A, Pell J, Greenwood R, et al.

Thyroid, 2019 04;29(4):563-572.
PMID: 30880626 DOI: 10.1089/thy.2018.0506

BACKGROUND: Previous in vitro experiments have demonstrated that prostaglandin F2-alpha (PF2α) reduced proliferation and adipogenesis in a murine cell line and human orbital fibroblasts derived from subjects with inactive Graves' orbitopathy (GO). The objective of this study was to determine if the PGF2α analogue bimatoprost is effective at reducing proptosis in this population.
METHODS: A randomized controlled double-masked crossover trial was conducted in a single tertiary care academic medical center. Patients with long-standing, inactive GO but persistent proptosis (>20 mm in at least one eye) were recruited. Allowing for a 15% dropout rate, 31 patients (26 females) were randomized in order to identify a treatment effect of 2.0 mm (p = 0.05; power 0.88). Following informed consent, participants were randomized to receive bimatoprost or placebo for three months, after which they underwent a two-month washout before switching to the opposite treatment. The primary outcome was the change in exophthalmometry readings over the two three-month treatment periods.
RESULTS: The mean exophthalmometer at baseline was 23.6 mm (range 20.0-30.5 mm), and the mean age of the patients was 55 years (range 28-74 years). The median duration of GO was 7.6 years (interquartile range 3.6-12.3 years). The majority were still suffering from diplopia (61.3%) with bilateral involvement (61.3%). Using multi-level modeling adjusted for baseline, period, and carry-over, bimatoprost resulted in a -0.17 mm (reduction) exophthalmometry change ([confidence interval -0.67 to +0.32]; p = 0.490). There was a mean change in intraocular pressure of -2.7 mmHg ([confidence interval -4.0 to -1.4]; p = 0.0070). One patient showed periorbital fat atrophy on treatment, which resolved on stopping treatment. Independent analysis of proptosis by photographic images (all subjects) and subgroup analysis on monocular disease (n = 12) did not show any apparent benefit.
CONCLUSIONS: In inactive GO, bimatoprost treatment over a three-month period does not result in an improvement in proptosis.
Fulltext Expression of Endogenous Putative TSH Binding Protein in Orbit

Draman MS, Grennan-Jones F, Taylor P, Muller I, Evans S, Haridas A, et al.

Curr Issues Mol Biol, 2021 Oct 27;43(3):1794-1804.
PMID: 34889904 DOI: 10.3390/cimb43030126

Thyroid stimulating antibodies (TSAB) cause Graves' disease and contribute to Graves' Orbitopathy (GO) pathogenesis. We hypothesise that the presence of TSH binding proteins (truncated TSHR variants (TSHRv)) and/or nonclassical ligands such as thyrostimulin (α2β5) might provide a mechanism to protect against or exacerbate GO. We analysed primary human orbital preadipocyte-fibroblasts (OF) from GO patients and people free of GO (non-GO). Transcript (QPCR) and protein (western blot) expression levels of TSHRv were measured through an adipogenesis differentiation process. Cyclic-AMP production by TSHR activation was studied using luciferase-reporter and RIA assays. After differentiation, TSHRv levels in OF from GO were significantly higher than non-GO (p = 0.039), and confirmed in ex vivo analysis of orbital adipose samples. TSHRv western blot revealed a positive signal at 46 kDa in cell lysates and culture media (CM) from non-GO and GO-OF. Cyclic-AMP decreased from basal levels when OF were stimulated with TSH or Monoclonal TSAB (M22) before differentiation protocol, but increased in differentiated cells, and was inversely correlated with the TSHRv:TSHR ratio (Spearman correlation: TSH r = -0.55, p = 0.23, M22 r = 0.87, p = 0.03). In the bioassay, TSH/M22 induced luciferase-light was lower in CM from differentiated GO-OF than non-GO, suggesting that secreted TSHRv had neutralised their effects. α2 transcripts were present but reduced during adipogenesis (p < 0.005) with no difference observed between non-GO and GO. β5 transcripts were at the limit of detection. Our work demonstrated that TSHRv transcripts are expressed as protein, are more abundant in GO than non-GO OF and have the capacity to regulate signalling via the TSHR.