Durable rust resistance in wheat is effective against multiple pathogens

Tese de doutoramento em Ciências da Saúde, no ramo de Medicina Dentária, apresentada à Faculdade de Medicina da Universidade de CoimbraA osteonecrose maxilar associada aos bifosfonatos, que se apresenta como uma lesão pós-cirúrgica associada a incapacidade de cicatrização, é um dos efeitos secundários mais frequentemente observados nos doentes submetidos a terapêutica com bifosfonatos nitrogenados. Assim, esta patologia é diagnosticada maioritariamente em doentes com metastização óssea, sob terapêutica com bifosfonatos nitrogenados intra-venosos. A fisiopatologia da osteonecrose maxilar associada aos bifosfonatos tem sido relacionada com a supressão da remodelação óssea, com a infeção local e com a toxicidade dos bifosfonatos nos tecidos envolventes, que mantém e perpetua a exposição óssea. Os fatores de risco da osteonecrose maxilar associada aos bifosfonatos foram categorizados em fatores relacionados com a terapêutica, que incluem a administração intravenosa em doenças oncológicas e a utilização do bifosfonato mais potente, o zoledronato; e factores locais, que incluem as exodontias, a colocação de implantes, a cirurgia periapical e a cirurgia periodontal que envolva os tecidos ósseos. No entanto, no caso da cirurgia periapical, não foram encontrados estudos que relacionem este procedimento com a osteonecrose maxilar. No contexto da toxicidade do zoledronato, uma vez que os compostos de fosfato de cálcio têm a capacidade de o adsorver, nomeadamente quando utilizados como sistemas transportadores de bifosfonatos, e são passíveis de aplicação nas locas cirúrgicas, constituindo substitutos ósseos adequados, colocou-se a hipótese de estes compostos poderem, potencialmente, ter um efeito protetor nos tecidos que envolvem as locas cirúrgicas. Assim, constituíram objetivos deste trabalho a avaliação da cirurgia periapical como desencadeadora de osteonecrose maxilar na presença de zoledronato e, paralelamente, a avaliação do potencial protetor da aplicação de compostos de fosfato de cálcio na loca cirúrgica. Para cumprir os objetivos propostos neste trabalho, realizaram-se estudos de química, estudos in vitro e estudos in vivo. No que respeita aos estudos de química, avaliou-se a reação entre o zoledronato e os compostos de fosfato de cálcio. Através de espetroscopia do visível e de análise elementar, verificou-se que o zoledronato é adsorvido, em solução aquosa, pelos compostos bifásicos de fosfato de cálcio. A etiologia da osteonecrose maxilar descreve um efeito deletério dos bifosfonatos nos tecidos moles, especialmente nos fibroblastos, que apresentam uma função insubstituível na cicatrização das lesões cirúrgicas orais. No contexto dos estudos in vitro, estabeleceram-se culturas primárias de fibroblastos gengivais humanos, que constituíram um modelo para avaliar a citotoxicidade na presença de zoledronato e na presença da associação zoledronato/compostos bifásicos de fosfato de cálcio. Avaliou-se a atividade metabólica dos fibroblastos gengivais humanos através do ensaio de MTT (brometo de 3-(4,5-dimetiltiazol-2-il)-2,5-difeniltetrazol), a sua viabilidade através do ensaio de SRB (ensaio da sulforrodamina B), os tipos de morte e o ciclo celular dos fibroblastos gengivais humanos através de citometria de fluxo e a capacidade de migração através do scratch assay. Verificou-se que o zoledronato apresentou um efeito citotóxico significativo nos fibroblastos gengivais humanos, com diminuição da atividade metabólica e da viabilidade, com aumento das populações celulares em morte por apoptose e por necrose e pela diminuição da capacidade de migração. Com a associação zoledronato/compostos bifásicos de fosfato de cálcio, foi possível diminuir, ou mesmo anular, a toxicidade do zoledronato, que se manifestou pela ausência de diferenças em relação aos grupos controlo. Nos estudos in vivo, foi utilizado um modelo experimental reprodutível já estudado, que relaciona diretamente a administração crónica de bifosfonatos com o desenvolvimento de osteonecrose maxilar após exodontia. Este modelo animal serviu como base ao desenvolvimento de um modelo de cirurgia apical com administração crónica de bifosfonatos. Os grupos de animais tratados foram submetidos a administração intra-peritoneal de zoledronato nas quatro semanas antecedentes à intervenção cirúrgica e nas duas ou três semanas seguintes. As mandíbulas foram avaliadas macroscopicamente, através da medicina nuclear, radiologia e histologia. No contexto da medicina nuclear, foi utilizado o radiofármaco 99mTc-zoledronato, que foi obtido após o desenvolvimento e a optimização de um procedimento de marcação radioquímica do zoledronato, e respetivo controlo de qualidade. Verificou-se que, nos animais submetidos à terapêutica com zoledronato, em que se desenvolveu a exodontia, existiu maior captação de 99mTc-zoledronato, menor densidade radiográfica e alterações histológicas compatíveis com cicatrização diminuída. Com a aplicação dos compostos bifásicos de fosfato de cálcio, não se observaram diferenças em relação aos animais controlo. No caso dos animais submetidos à cirurgia apical, não se verificaram alterações significativas em relação aos animais controlo, nos animais submetidos à terapêutica com zoledronato, tanto na presença como na ausência da aplicação de compostos bifásicos de fosfato de cálcio. Este trabalho de investigação permitiu elucidar acerca dos desígnios que deram origem a esta tese. No modelo animal de cirurgia periapical desenvolvido, não foi observado um atraso significativo da cicatrização nem sinais da osteonecrose maxilar, nos tempos avaliados, concluindo-se que a terapêutica com zoledronato poderá não constituir um fator de risco nesta intervenção cirúrgica. Pelo contrário, no modelo animal de exodontia confirmou-se que, efetivamente, o zoledronato constitui um fator de risco, e que os compostos bifásicos de fosfato de cálcio, apresentam potencial efeito protetor da toxicidade inerente aos bifosfonatos. Esta conclusão foi sustentada pelos estudos de química, em que se verificou a adsorção do zoledronato, corroborada por supressão da toxicidade nos estudos in vitro e cicatrização favorecida no modelo animal de exodontia com administração crónica de zoledronato.Bisphosphonate-associated osteonecrosis of the jaw, a post-surgical non-healing wound condition, is one of the most often seen side effects in patients treated with nitrogencontaining bisphosphonates. Therefore, this pathology is primarily diagnosed in patients with metastatic bone disease, receiving intravenous administration of nitrogen-containing bisphosphonates. Bisphosphonate-associated osteonecrosis of the jaw physiopathology has been related with suppression of bone turnover, local infections or soft tissue toxicity. Recent studies associate the physiopathological mechanisms of the osteonecrosis of the jaw with toxic effects of bisphosphonates on different cell types, besides osteoclast, being the most important cause of soft tissues toxicity that contributes for the maintenance of bone exposure. Bisphosphonate-associated osteonecrosis of the jaw risk factors were categorized as drug-related factors, including intravenous administration in oncological diseases and the use of the most potent bisphosphonate, zoledronate; and local factors including, dental extractions, dental implant placement, periapical surgery and periodontal surgery involving osseous injury. However, there are no studies that relate periapical surgery with osteonecrosis of the jaw. Considering zoledronate toxicity, since calcium phosphate compounds are able to adsorb it, namely when used as drug delivery vehicle, and are also used in surgical wounds, as a bone substitute, it was hypothesised this compounds had a potential protective effect to the soft tissues surrounding surgical osseous wounds. Thus, the aim of this study was to assess periapical surgery as a trigger of osteonecrosis of the jaw in the presence of zoledronate and also the potential protective effect of calcium phosphate compounds when applied in the surgical wound. To fulfil the proposed objectives of this work were carried out studies of chemistry, in vitro and in vivo studies. Regarding chemical studies, it was evaluated the chemical reaction between zoledronate and calcium phosphate compounds. Through ultraviolet-visible spectroscopy and elemental analysis it has been found that zoledronate, in aqueous solution, was adsorbed by biphasic calcium phosphate compounds. Bisphosphonate-associated osteonecrosis of the jaw aetiology describes a deleterious effect of bisphosphonates on soft tissues, especially on fibroblasts, which play an important role in oral wound healing. Considering in vitro studies it was established a primary culture of human gingival fibroblasts that constituted a model to evaluate the cytotoxicity in the presence of zoledronate and of zoledronate/biphasic calcium phosphate compounds association. It was investigated the metabolic activity of human gingival fibroblasts through MTT (3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, cell viability through SRB (sulforhodamine B) assay, types of cell death and cell cycle through flow cytometry and migration ability of human gingival fibroblasts through scratch assay. It was verified that zoledronate had a strong cytotoxic effect in the human gingival fibroblasts, by the reduction of metabolic activity, cell viability, increase of cells in apoptosis and reduction of migration. With the association zoledronate/biphasic calcium phosphate compounds it was possible to reduce or abolish zoledronate toxicity, as it was demonstrated by the absence of differences related to control. In the in vivo study it was used a reproducible experimental model that directly relates chronic bisphosphonate administration with the development of osteonecrosis of the jaw with tooth extraction. This animal model also served as basis to the development of a osteotomy in periapical surgery model with chronic bisphosphonate administration. The animals were treated with zoledronate intraperitoneally, during the four weeks that preceded the surgeries and in the following two and three weeks. The mandibles were macroscopic evaluated, examined by nuclear medicine, radiology and histologically analysed. Concerning nuclear medicine it was used the radiopharmaceutical 99mTc-zoledronate, which was obtained after the development and optimization of a procedure for zoledronate radiochemical labelling, and respective quality control. It has been found that the animals with zoledronate, submitted to tooth extraction, had a higher 99mTc-zoledronate uptake, lower radiological density and histologic images compatible with a decreased healing. With biphasic calcium phosphate compounds application, there were no differences related to controls. In the animals submitted to osteotomy in periapical surgery there were no significant differences related to the controls, in both animals with zoledronate, with and without biphasic calcium phosphate compounds application. This research work allowed the clarification of the goals that led to this thesis. In the created animal model of osteotomy in periapical surgery, it was not observed a significant delay in the wound healing, neither osteonecrosis of the jaw, in the evaluated periods, therefore it was conclude that zoledronate therapeutic may not constitute a risk factor in this surgical approach. Contrarily, in the tooth extraction animal model, it was confirmed that zoledronate therapeutic constitute a risk factor, and it was found that biphasic calcium phosphate compounds presents a potential protector effect from bisphosphonates toxicity. This conclusion was supported by the chemical studies, in which it was observed adsorption of zoledronate, corroborated by the lower toxicity in the in vitro studies and by the improved cicatrisation in the tooth extraction animal model with chronic bisphosphonates administration

Increasing pCO2 correlates with low concentrations of intracellular dimethylsulfoniopropionate in the sea anemone Anemonia viridis.

Marine anthozoans maintain a mutualistic symbiosis with dinoflagellates that are prolific producers of the algal secondary metabolite dimethylsulfoniopropionate (DMSP), the precursor of the climate-cooling trace gas dimethyl sulfide (DMS). Surprisingly, little is known about the physiological role of DMSP in anthozoans and the environmental factors that regulate its production. Here, we assessed the potential functional role of DMSP as an antioxidant and determined how future increases in seawater pCO2 may affect DMSP concentrations in the anemone Anemonia viridis along a natural pCO2 gradient at the island of Vulcano, Italy. There was no significant difference in zooxanthellae genotype and characteristics (density of zooxanthellae, and chlorophyll a) as well as protein concentrations between anemones from three stations along the gradient, V1 (3232 μatm CO2), V2 (682 μatm) and control (463 μatm), which indicated that A. viridis can acclimate to various seawater pCO2. In contrast, DMSP concentrations in anemones from stations V1 (33.23 ± 8.30 fmol cell(-1)) and V2 (34.78 ± 8.69 fmol cell(-1)) were about 35% lower than concentrations in tentacles from the control station (51.85 ± 12.96 fmol cell(-1)). Furthermore, low tissue concentrations of DMSP coincided with low activities of the antioxidant enzyme superoxide dismutase (SOD). Superoxide dismutase activity for both host (7.84 ± 1.37 U·mg(-1) protein) and zooxanthellae (2.84 ± 0.41 U·mg(-1) protein) at V1 was 40% lower than at the control station (host: 13.19 ± 1.42; zooxanthellae: 4.72 ± 0.57 U·mg(-1) protein). Our results provide insight into coastal DMSP production under predicted environmental change and support the function of DMSP as an antioxidant in symbiotic anthozoans

Genetic improvement of wheat for dry environments - a trait based approach

Item does not contain fulltext23 januari 201

Repeat-length variation in a wheat cellulose synthase-like gene is associated with altered tiller number and stem cell wall composition

The tiller inhibition gene (tin) that reduces tillering in wheat (Triticum aestivum) is also associated with large spikes, increased grain weight, and thick leaves and stems. In this study, comparison of near-isogenic lines (NILs) revealed changes in stem morphology, cell wall composition, and stem strength. Microscopic analysis of stem cross-sections and chemical analysis of stem tissue indicated that cell walls in tin lines were thicker and more lignified than in free-tillering NILs. Increased lignification was associated with stronger stems in tin plants. A candidate gene for tin was identified through map-based cloning and was predicted to encode a cellulose synthase-like (Csl) protein with homology to members of the CslA clade. Dinucleotide repeat-length polymorphism in the 5′UTR region of the Csl gene was associated with tiller number in diverse wheat germplasm and linked to expression differences of Csl transcripts between NILs. We propose that regulation of Csl transcript and/or protein levels affects carbon partitioning throughout the plant, which plays a key role in the tin phenotype.J. Hyles, S. Vautrin, F. Pettolino, C. MacMillan, Z. Stachurski, J. Breen, H. Berges, T. Wicker, and W. Spielmeye

Major haplotype divergence including multiple germin-like protein genes, at the wheat Sr2 adult plant stem rust resistance locus

Background The adult plant stem rust resistance gene Sr2 was introgressed into hexaploid wheat cultivar (cv) Marquis from tetraploid emmer wheat cv Yaroslav, to generate stem rust resistant cv Hope in the 1920s. Subsequently, Sr2 has been widely deployed and has provided durable partial resistance to all known races of Puccinia graminis f. sp. tritici. This report describes the physical map of the Sr2-carrying region on the short arm of chromosome 3B of cv Hope and compares the Hope haplotype with non-Sr2 wheat cv Chinese Spring. Results Sr2 was located to a region of 867 kb on chromosome 3B in Hope, which corresponded to a region of 567 kb in Chinese Spring. The Hope Sr2 region carried 34 putative genes but only 17 were annotated in the comparable region of Chinese Spring. The two haplotypes differed by extensive DNA sequence polymorphisms between flanking markers as well as by a major insertion/deletion event including ten Germin-Like Protein (GLP) genes in Hope that were absent in Chinese Spring. Haplotype analysis of a limited number of wheat genotypes of interest showed that all wheat genotypes carrying Sr2 possessed the GLP cluster; while, of those lacking Sr2, some, including Marquis, possessed the cluster, while some lacked it. Thus, this region represents a common presence-absence polymorphism in wheat, with presence of the cluster not correlated with presence of Sr2. Comparison of Hope and Marquis GLP genes on 3BS found no polymorphisms in the coding regions of the ten genes but several SNPs in the shared promoter of one divergently transcribed GLP gene pair and a single SNP downstream of the transcribed region of a second GLP. Conclusion Physical mapping and sequence comparison showed major haplotype divergence at the Sr2 locus between Hope and Chinese Spring. Candidate genes within the Sr2 region of Hope are being evaluated for the ability to confer stem rust resistance. Based on the detailed mapping and sequencing of the locus, we predict that Sr2 does not belong to the NB-LRR gene family and is not related to previously cloned, race non-specific rust resistance genes Lr34 and Yr36

AB-QTL analysis in winter wheat: II. Genetic analysis of seedling and field resistance against leaf rust in a wheat advanced backcross population

The present study aimed to localize exotic quantitative trait locus (QTL) alleles for the improvement of leaf rust (P.triticina) resistance in an advanced backcross (AB) population, B22, which is derived from a cross between the winter wheat cultivar Batis (Triticumaestivum) and the synthetic wheat accession Syn022L. The latter was developed from hybridization of T.turgidum ssp. dicoccoides and T.tauschii. Altogether, 250 BC2F3 lines of B22 were assessed for seedling resistance against the leaf rust isolate 77WxR under controlled conditions. In addition, field resistance against leaf rust was evaluated by assessing symptom severity under natural infestation across multiple environments. Simultaneously, population B22 was genotyped with a total of 97 SSR markers, distributed over the wheat A, B and D genomes. The phenotype and genotype data were subjected to QTL analysis by applying a 3-factorial mixed model analysis of variance including the marker genotype as a fixed effect and the environments, the lines and the marker by environment interactions as random effects. The QTL analysis revealed six putative QTLs for seedling resistance and seven for field resistance. For seedling resistance, the effects of exotic QTL alleles improved resistance at all detected loci. The maximum decrease of disease symptoms (−46.3%) was associated with marker locus Xbarc149 on chromosome 1D. For field resistance, two loci had stable main effects across environments and five loci exhibited marker by environment interaction effects. The strongest effects were detected at marker locus Xbarc149 on chromosome 1D, at which the exotic allele decreased seedling symptoms by 46.3% and field symptoms by 43.6%, respectively. Some of the detected QTLs co-localized with known resistance genes, while others appear to be as novel resistance loci. Our findings indicate, that the exotic wheat accession Syn022L may be useful for the improvement of leaf rust resistance in cultivated wheat