Characterisation and mapping of adult plant stripe rust resistance in wheat accession Aus27284

Key message

A new adult plant stripe rust resistance gene, Yr80, was identified in a common wheat landrace Aus27284. Linked markers were developed and validated for their utility in marker-assisted selection.

Abstract

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is among the most important constraints to global wheat production. The identification and characterisation of new sources of host plant resistance enrich the gene pool and underpin deployment of resistance gene pyramids in new cultivars. Aus27284 exhibited resistance at the adult plant stage against predominant Pst pathotypes and was crossed with a susceptible genotype Avocet S. A recombinant inbred line (RIL) population comprising 121 lines was developed and tested in the field at three locations in 2016 and two in 2017 crop seasons. Monogenic segregation for adult plant stripe rust response was observed among the Aus27284/Avocet S RIL population and the underlying locus was temporarily designated YrAW11. Bulked-segregant analysis using the Infinium iSelect 90K SNP wheat array placed YrAW11 in chromosome 3B. Kompetitive allele specific PCR (KASP) primers were designed for the linked SNPs and YrAW11 was flanked by KASP_65624 and KASP_53292 (3 cM) proximally and KASP_53113 (4.9 cM) distally. A partial linkage map of the genomic region carrying YrAW11 comprised nine KASP and two SSR markers. The physical position of KASP markers in the pseudomolecule of chromosome 3B placed YrAW11 in the long arm and the location of markers gwm108 and gwm376 in the deletion bin 3BL2-0.22 supported this conclusion. As no other stripe rust resistance locus has been reported in chromosome 3BL, YrAW11 was formally designated Yr80. Marker KASP_ 53113 was polymorphic among 94% of 81 Australian wheat cultivars used for validation.

     

Role of inhibitors in the induction of differentiation in callus cultures of Brassica,Datura and Nicotiana

The effect of various inhibitors on differentiation (shoot morphogenesis) in callus cultures of Brassica, Datura and Nicotiana has been investigated. Hormone medium without any inhibitor (control), resulted in 6% shoot formation. Addition of inhibitors such as actinomycin D, cordycepin, abscisic acid, trigonelline and theophylline greatly enhanced shoot formation. The results suggest that inhibitors play a regulatory role in the control of differentiation.Abbreviations ABA Abscisic acid - BA Benzyl adenine - Kn Kinetin - MS Murashige Skoog's - NAA 1-naphthalene acetic acid     

P311 binds to the latency associated protein and downregulates the expression of TGF-beta1 and TGF-beta2

P311 is an 8-kDa protein originally found in neurons and muscle. We recently showed that expression of P311 in NIH 3T3 cells induced a myofibroblast phenotype with low TGF-beta1 expression. Here we demonstrate that P311 downregulates not only TGF-beta1, but also TGF-beta2, expression, with no effect on TGF-beta3. In addition, P311 interacts with TGF-beta2 in a yeast two-hybrid system through a sequence encompassing part of the TGF-beta latent associated protein (LAP) and part of mature TGF-beta2. Coimmunoprecipitations demonstrated interaction between P311 and TGF-beta1 and 2, but not TGF-beta3. Additional coimmunoprecipitations after introducing LAP or mature TGF-beta1 into cells demonstrated P311 binding to LAP, but not to mature TGF-beta. P311 has a conserved PEST domain, which generally serves as a rapid degradation signal. Deletion of the PEST domain reversed the effect of P311 on TGF-beta isoforms. Finally, Smad3 activity was decreased in P311-expressing cells, but was corrected by exogenous TGF-beta1 treatment, which also elevated TGF-beta1 mRNA level. This suggested that P311 downregulates TGF-beta1 and 2 in part by blocking TGF-beta autoinduction.     

Genetics of durable resistance to leaf rust and stripe rust of an Indian wheat cultivar HD2009

The Indian bread wheat cultivar HD2009 has maintained its partial resistance to leaf rust and stripe rust in India since its release in 1976. To examine the nature, number and mode of inheritance of its genes for partial leaf rust and stripe rust resistance, this cultivar was crossed with cultivar WL711, which is susceptible to leaf rust and stripe rust. The F1, F2, F3 and F5 generations from this cross were assessed separately for adult plant disease severity under artificial epidemic of race 77-5 of leaf rust and race 46S119 of stripe rust. Segregation for rust reaction in the F2, F3 and F5 generations indicated that resistance to each of these rust diseases is based on 2 genes, each with additive effects. Although the leaf rust resistance of HD2009 is similar in expression to that conferred by the gene Lr34, but unlike the wheats carrying this gene, cultivar HD2009 did not show leaf tip necrosis, a morphological marker believed to be tightly linked to the leaf rust resistance gene Lr34. Thus, the non-hypersensitive resistance of HD2009 was ascribed to genes other than Lr34.     

Immuno capture PCR for rapid and sensitive identification of pathogenic Bacillus anthracis

Immuno capture PCR (IPCR) is a technique capable of detecting the pathogens with high specificity and sensitivity. Rapid and accurate detection of Bacillus anthracis was achieved using anti-EA1 antibodies to capture the cells and two primer sets targeting the virulence factors of the pathogen i.e., protective antigen (pag) and capsule (cap) in an IPCR format. Monoclonal antibodies specific to B. anthracis were generated against extractable antigen 1 protein and used as capture antibody onto 96 well polystyrene plates. Following the binding of the pathogen, the DNA extraction was carried out in the well itself and further processed for PCR assay. We compared IPCR described here with conventional duplex PCR using the same primers and sandwich ELISA using the monoclonal antibodies developed in the present study. IPCR was capable of detecting as few as 10 and 100 cfu ml^?1 of bacterial cells and spores, respectively. IPCR was found to be 2–3 logs more sensitive than conventional duplex PCR and the sandwich ELISA. The effect of other bacteria and any organic materials on IPCR was also analyzed and found that this method was robust with little change in the sensitivity in the presence of interfering agents. Moreover, we could demonstrate a simple process of microwave treatment for spore disruption which otherwise are resistant to chemical treatments. Also, the IPCR could clearly distinguish the pathogenic and nonpathogenic strains of B. anthracis in the same assay. This can help in saving resources on unnecessary decontamination procedures during false alarms.     

HSP70 Domain II of Mycobacterium tuberculosis Modulates Immune Response and Protective Potential of F1 and LcrV Antigens of Yersinia pestis in a Mouse Model

No ideal vaccine exists to control plague, a deadly dangerous disease caused by Yersinia pestis. In this context, we cloned, expressed and purified recombinant F1, LcrV antigens of Y. pestis and heat shock protein70 (HSP70) domain II of M. tuberculosis in E. coli. To evaluate the protective potential of each purified protein alone or in combination, Balb/C mice were immunized. Humoral and cell mediated immune responses were evaluated. Immunized animals were challenged with 100 LD₅₀ of Y. pestis via intra-peritoneal route. Vaccine candidates i.e., F1 and LcrV generated highly significant titres of anti-F1 and anti-LcrV IgG antibodies. A significant difference was noticed in the expression level of IL-2, IFN-γ and TNF-α in splenocytes of immunized animals. Significantly increased percentages of CD4+ and CD8+ T cells producing IFN-γ in spleen of vaccinated animals were observed in comparison to control group by flow cytometric analysis. We investigated whether the F1, LcrV and HSP70(II) antigens alone or in combination can effectively protect immunized animals from any histopathological changes. Signs of histopathological lesions noticed in lung, liver, kidney and spleen of immunized animals on 3^rd day post challenge whereas no lesions in animals that survived to day 20 post-infection were observed. Immunohistochemistry showed bacteria in lung, liver, spleen and kidney on 3^rd day post-infection whereas no bacteria was observed on day 20 post-infection in surviving animals in LcrV, LcrV+HSP70(II), F1+LcrV, and F1+LcrV+HSP70(II) vaccinated groups. A significant difference was observed in the expression of IL-2, IFN-γ, TNF-α, and CD4+/CD8+ T cells secreting IFN-γ in the F1+LcrV+HSP70(II) vaccinated group in comparison to the F1+LcrV vaccinated group. Three combinations that included LcrV+HSP70(II), F1+LcrV or F1+LcrV+HSP70(II) provided 100% protection, whereas LcrV alone provided only 75% protection. These findings suggest that HSP70(II) of M. tuberculosis can be a potent immunomodulator for F1 and LcrV containing vaccine candidates against plague.     

Inheritance of leaf rust resistance in wheat lines carryingAegilops speltoides Tausch. translocation in Chinese Spring background

The genetic basis of seedling and adult-plant leaf rust resistance was analysed in wheat lines CS 2A/2M 4/2 and CS 2D/2M 3/8, which are reference lines for the leaf rust resistance gene Lr28. Some seedlings of CS 2A/2M 4/2 were susceptible to Indian Puccinia triticina (Pt) pathotypes 77-1, 77-2 and 77-5. These susceptible seedlings exhibited resistance at the adult-plant growth stage. In contrast, CS 2D/2M 3/8 showed resistance to all Pt pathotypes both at the seedling and adult-plant growth stages. The analysis of inheritance in the susceptible plants of CS 2A/2M 4/2 (CS 2A/2M 4/2 APR selection) and CS 2D/2M 3/8 against Pt 77-5 (the frequently occurring Pt pathotype from the Indian subcontinent), indicated that line CS 2D/2M 3/8 was fixed for a dominant gene, presumed to be Lr28, whereas line CS 2A/2M 4/2 was heterogeneous for Lr28. The adult-plant resistance in the CS 2A/2M 4/2 APR selection was conferred by an unknown recessive gene.