Kinetic and thermodynamic behaviour of wall-bound peroxidase from wheat leaves infected with stripe rust

We have identified two types of peroxidases (POX), one ionically and one covalently bound to the particulate fraction, in stripe rust-infected and -uninfected wheat (Triticum aestivum L.) leaves. The cell walls contained a high level of POX, of which 73–76% was extractable by 1% NaCl and 24–26% by 5 mM EDTA in infected and non-infected leaves of HD 2329. The NaCl-released POX constituted the predominant fraction. Both NaCl- and EDTA-extracted POX exhibited maximum activity at pH 5.0 and had a K _m (enzyme–substrate affinity measure) value of 1.61–1.70 and 1.64–1.67 mM, respectively, with o-dianisidine as the substrate. The V _max (maximum catalytic rate) in the two extractions ranged between 7.06–7.45 and 6.65–7.82 μmol min⁻¹ g⁻¹ fresh weight. A temperature optimum of 50°C was observed for both the NaCl- and EDTA-released fractions. The two POX fractions showed a differential response to metal ions, suggesting their distinctive nature. Sodium azide inhibited POX activity markedly, which suggested the presence of heme as a prosthetic group. Inhibition of wall-bound POX by iodine and the regeneration of activity by mercaptoethanol suggested the involvement of cysteine in the active site of the enzyme. These two forms showed greater differences in terms of thermodynamic properties, such as the energy of activation (E _a) and enthalpy change (ΔH), while entropy (ΔS) and free energy changes were similar. The results further show that pathogen infection of the leaves of this susceptible wheat cultivar induces an increase in the activity and kinetics of POX, which may be critical in the response of the plant cell to infection.     

Changes in proteins and isoenzymes in leaves of wheat when infected by stem rust

Summary Biuret assay, gel electrophoresis and immunochemistry were used to study concentrations, forms and activities of proteins of uredospores of Puccinia graminis Pers. f. sp. tritici, in healthy wheat leaves, wheat leaves that had been inoculated with incompatible races of stem rust and leaves which had become rusted.The soluble proteins of primary leaves increased by 25–117% following infection by compatible races of stem rust. There was a corresponding decrease of proteins in uninfected younger leaves. Infection by an incompatible strain of rust led to a temporary 29% increase in soluble proteins.Immunoelectrophoresis and gel electrophoresis of infected leaves showed the presence in them of the forms of malate dehydrogenase, glucose-6-phosphate dehydrogenase, catalase and -amylase characteristic of the rust fungus. In the infected leaves, the activity of certain bands of host glucose-6-phosphate dehydrogenase and catalase changed with the development of the pathogen; the malate dehydrogenase and -amylase of the host were unaffected. In leaves inoculated with an incompatible race there were no obvious changes of any of these enzymes.     

Characterization of non-host resistance in broad bean to the wheat stripe rust pathogen

ABSTRACT: BACKGROUND: Non-host resistance (NHR) confers plant species immunity against the majority of microbialpathogens and represents the most robust and durable form of plant resistance in nature. Asone of the main genera of rust fungi with economic and biological importance, Puccinia infects almost all cereals but is unable to cause diseases on legumes. Little is known about themechanism of this kind of effective defense in legumes to these non-host pathogens. RESULTS: In this study, the basis of NHR in broad bean (Vicia faba L.) against the wheat stripe rustpathogen, Puccinia striiformis f. sp. tritici (Pst), was characterized. No visible symptomswere observed on broad bean leaves inoculated with Pst. Microscopic observations showedthat successful location of stomata and haustoria formation were significantly reduced in Pstinfection of broad bean. Attempted infection induced the formation of papillae, cell wallthickening, production of reactive oxygen species, callose deposition and accumulation ofphenolic compounds in plant cell walls. The few Pst haustoria that did form in broad beancells were encased in reactive oxygen and callose materials and those cells elicited cell death.Furthermore, a total of seven defense-related genes were identified and found to be upregulatedduring the Pst infection. CONCLUSIONS: The results indicate that NHR in broad bean against Pst results from a continuum of layereddefenses, including basic incompatibility, structural and chemical strengthening of cell wall,posthaustorial hypersensitive response and induction of several defense-related genes,demonstrating the multi-layered feature of NHR. This work also provides useful informationfor further determination of resistance mechanisms in broad bean to rust fungi, especially theadapted important broad bean rust pathogen, Uromyces viciae-fabae, because of strongsimilarities and association between NHR of plants to unadapted pathogens and basalresistance of plants to adapted pathogens.     

Identification of adult plant resistance to stripe rust in the wheat cultivar Cappelle-Desprez

Following the appearance of stripe rust in South Africa in 1996, efforts have been made to identify new sources of durable resistance. The French cultivar Cappelle-Desprez has long been considered a source of durable, adult plant resistance (APR) to stripe rust. As Cappelle-Desprez contains the seedling resistance genes Yr3a and Yr4a, wheat lines were developed from which Yr3a and Yr4a had been removed, while selecting for Cappelle-Desprez derived APR effective against South African pathotypes of the stripe rust fungus, Puccinia striiformis f. sp. tritici. Line Yr16DH70, adapted to South African wheat growing conditions, was selected and crossed to the stripe rust susceptible cultivar Palmiet to develop a segregating recombinant inbred line mapping population. A major effect QTL, QYr.ufs-2A was identified on the short arm of chromosome 2A derived from Cappelle-Desprez, along with three QTL of smaller effect, QYr.ufs-2D, QYr.ufs-5B and QYr.ufs-6D. QYr.ufs-2D was located within a region on the short arm of chromosome 2D believed to be the location of the stripe rust resistance gene Yr16. An additional minor effect QTL, QYr.ufs-4B, was identified in the cv. Palmiet. An examination of individual RILs carrying single or combinations of each QTL indicated significant resistance effects when QYr.ufs-2A was combined with the three minor QTL from Cappelle-Desprez, and between QYr.ufs-2D and QYr.ufs-5B.     

Potential oversummering and overwintering regions for the wheat stripe rust pathogen in the contiguous United States

Epidemics of wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), are more frequent in the regions where Pst can oversummer and overwinter. Regions for potential oversummering and overwintering of Pst were determined in the contiguous United States using a survival index (SI) ranging from 0 (most unfavorable) to 10 (most favorable) developed based on long-term weather data. The pathogen can survive in cool summer in the most regions north of latitude 40°N, particularly Washington, Idaho, Montana, Oregon and California. Due to limiting high temperatures, it survives marginally during summer in Arkansas, Delaware, Georgia, Iowa, Illinois, Indiana, Kansas, Kentucky, Massachusetts, Missouri, Ohio, Oklahoma, Rhode Island and Texas. Similarly, unfavorable hot summer restricts summer survival of the pathogen in the most regions south of 40°N except for highlands in the Rocky or Appalachian Mountains. Warm winters favor fungal survival in most regions south of 40°N and the Pacific Coast, including Alabama, Arkansas, Arizona, California, Florida, Georgia, Idaho, Louisiana, Mississippi, New Mexico, Nevada, Oregon, South Carolina, Texas and Washington. Severe winters do not allow survival in most regions north of 40°N and east of the Rocky Mountains, whereas less severe winter in Delaware, Illinois, Indiana, Kansas, Kentucky, Massachusetts, Maryland, Michigan, Missouri, North Carolina, New Jersey, New York, Ohio, Oklahoma, Pennsylvania, Rhode Island, Tennessee, Utah and Virginia permits marginal survival of Pst. Most wheat-growing regions have climatic suitability for either oversummering or overwintering. Both oversummering and overwintering can occur in the Pacific Northwest (Idaho, Oregon and Washington), Arizona, California, North Carolina, New Mexico, Pennsylvania, Virginia and West Virginia. These regions may provide primary inoculum for stripe rust epidemics in their own and surrounding regions.     

Identification and characterization of stripe rust resistance gene Yr34 in common wheat

An uncharacterized source of seedling resistance to Puccinia striiformis f.sp. tritici was identified in an advanced wheat breeding line WAWHT2046. Genetic analysis based on a WAWHT2046/Carnamah-derived double haploid (DH) population demonstrated monogenic inheritance of seedling stripe rust resistance in WAWHT2046. The gene controlling stripe rust resistance in line WAWHT2046 was tentatively designated YrWA. The chromosome 5AL located awn inhibitor gene B1, possessed by WAWHT2046, also showed monogenic inheritance when the DH population was scored for the presence and absence of awns. Joint segregation analysis at the B1 and YrWA loci indicated genetic linkage between the two loci. A recombination value of 12.2 cM was computed using Mapmanager. This association located YrWA in the chromosome arm 5AL. Molecular mapping using microsatellite markers placed YrWA distal to B1. All molecular markers mapped proximal to the awn inhibitor locus B1. As no other stripe rust resistance gene is reported to be located in the chromosome arm 5AL, YrWA was permanently designated as Yr34. Yr34 produced an intermediate (23C) seedling infection type and expressed very low stripe rust response (10R-MR) on adult plants in the field, similar to the resistance gene Yr17. In addition to Yr34, this mapping population segregated for three genetically independent adult plant stripe rust resistance genes. The detection of DH lines with completely susceptible response, higher than that shown by the Yr34-lacking parent Carnamah, suggested that both parents contributed adult plant resistance. The use of WAWHT2046 as a parent in breeding programs would also contribute APR in addition to Yr34.     

Teliospore-inducing activity for wheat leaf rust in the extracts of various host plant leaves infected with telia of rust fungi

MeOH and water extracts were obtained from 16 species of infected leaves with rust fungi belonging to 18 species in 6 families: Pucciniaceae, Melampsoraceae, Coleosporiaceae, Pileolariaceae, Phragmidiaceae, and Phakopsoraceae. All the extracts of rust-infected plants with telia showed the teliospore-inducing activity for wheat leaf rust (Puccinia recondita f. sp. tritici).     

低聚糖诱导小麦抗条锈性及相关酶活性变化的研究

用自行设计的方法从植物细胞壁中得到的低聚糖提取物5号对小麦浸种和苗期喷雾处理,均使接种条锈菌的小麦叶片产生了明显的过敏性坏死反应。对几种与抗病性密切相关的酶活性变化的分析表明,经低聚糖预先处理能显著提高小麦叶片的过氧化物酶(POD)、多酚氧化酶(PPO)和苯丙氨基酸解氨酶(PAL)的活性。     

Quantitative trait loci of stripe rust resistance in wheat

Key message

Over 140 QTLs for resistance to stripe rust in wheat have been published and through mapping flanking markers on consensus maps, 49 chromosomal regions are identified.

Abstract

Over thirty publications during the last 10 years have identified more than 140 QTLs for stripe rust resistance in wheat. It is likely that many of these QTLs are identical genes that have been spread through plant breeding into diverse backgrounds through phenotypic selection under stripe rust epidemics. Allelism testing can be used to differentiate genes in similar locations but in different genetic backgrounds; however, this is problematic for QTL studies where multiple loci segregate from any one parent. This review utilizes consensus maps to illustrate important genomic regions that have had effects against stripe rust in wheat, and although this methodology cannot distinguish alleles from closely linked genes, it does highlight the extent of genetic diversity for this trait and identifies the most valuable loci and the parents possessing them for utilization in breeding programs. With the advent of cheaper, high throughput genotyping technologies, it is envisioned that there will be many more publications in the near future describing ever more QTLs. This review sets the scene for the coming influx of data and will quickly enable researchers to identify new loci in their given populations.     

Diallel analysis of the latent period of stripe rust in wheat

A half diallel was made amongst five wheat (Triticum aestivum L.) genotypes of which one was susceptible, while the others had adult-plant resistance, to stripe rust (Puccinia striiformis West.). The five parent and ten F₁ progeny were grown in the glasshouse and were inoculated with three rust pathotypes at the seedling stage. The latent period was measured on the first leaf. Two procedures were used to analyze the half diallel. Both methods showed that the average effects of alleles were of much greater importance than was dominance in conditioning resistance in response to two of the pathotypes, while for the third pathotype dominance was important. Resistance was conditioned by partial dominance for two pathotypes whereas for the third it was determined by full dominance. Broad-sense heritabilities range from 60–73% and the number of genes involved was different (from 1 to 4), depending on the pathotype.     

小麦与条锈菌互作中过氧化物酶的细胞化学研究

采用细胞化学方法对小麦与条锈菌互作过程中过氧化物酶的分布及其活性大小进行了研究,结果表明：过氧化物酶主要分布于细胞壁和细胞间隙中;在未行接种的小麦叶片中,抗病品种和感病品种的过氧化物酶活性均比较低;条锈菌侵染后,诱导抗、感病品种叶片中的过氧化物酶活性升高,且抗病品种升高的幅度明显大于感病品种;感病品种中过氧化物酶活性在侵染位点附近细胞壁上表现升高,而抗病品种中该酶的活性在侵染点细胞以及远离侵染点的叶肉细胞的细胞壁和细胞间隙中均显著升高。高活性的过氧化物酶是小麦抗条锈性的生化标记和重要机制之一。     

Atmospheric teleconnection patterns associated with wheat stripe rust disease in North China

 Previous work has shown that long-term (>40 years) time series of wheat stripe rust disease from North China contain a signal related to the Southern Oscillation Index (SOI). However, no cause-and-effect relationships or direct links between SOI and disease have been established. Because mid-latitude teleconnection patterns form important links between global atmospheric variations and regional weather anomalies, such as the Southern Oscillation, studies of such patterns could result in a better physical and biological interpretation for the SOI-disease association observed previously. We used cross-spectral analyses to determine if and on which time scales severity of stripe rust in five regions of North China between 1952 and 1990 was associated with fluctuations in four Northern Hemisphere teleconnection patterns. These included the Pacific/North American, the Western Atlantic, the Western Pacific, and the Eurasian patterns. The analysis showed consistent and significant (P≤0.10) coherence relationships between the Western Atlantic (WA) pattern and stripe rust severity at a periodicity of 3.00 years. The phase relationships showed that, at the 3.00-year periodicity, the WA series and the disease series were out of phase by about half a period in all five regions. This phase difference indicated that peaks in the WA series, which are associated with below-normal winter temperatures over much of China, coincided with troughs in the disease series (i.e. low disease severity), presumably because of the negative effect of low winter temperatures on survival of the stripe rust pathogen. The analysis further showed that the WA series and the SOI series were highly significantly (P≤0.01) coherent at a periodicity of 4.33 years, which could explain the association between SOI and stripe rust severity reported previously. Received: 12 February 1997 / Accepted: 18 May 1998     

条锈病对小麦(Triticum aestivum L.)叶片光合功能及光合功能蛋白D1表达的影响

测定了小麦(Triticum aestivum L.)感染小麦条锈病后的光合常数,以及叶绿素含量、类囊体膜光合电子传递速率和光合反应中心D1蛋白的变化.实验显示,条锈病侵染导致感病小麦叶片净光合速率与叶绿素含量降低;抗病小麦经侵染后净光合速率却有恢复过程,叶绿素含量先降后升.此外,感病小麦叶片被侵染后全链电子传递速率受到抑制,PSII电子传递速率的变化与全链电子传递速率的变化趋势相似,但PSI电子传递速率受到的影响较小;抗病小麦小麦叶片被侵染后电子传递速率所受影响较小.同时发现,病程中,感病和抗病小麦PSII的光合反应中心D1蛋白含量变化总是与PSII电子传递速率的变化类似,推测D1蛋白的表达量变化是引起PSII电子传递活性与全链电子传递速率变化的主要因素之一.     

Identification of proteins with altered expression in colorectal cancer by means of 2D-proteomics

Modern proteomic techniques make it possible to identify numerous changes in protein expression in tumors as compared to normal tissues. Although proteomics is currently widely used, identification of proteins differentially expressed in particular types of cancer remains a challenging task. The goal of our study was to detect novel protein markers of colorectal cancer using comparative proteomics of protein extracts obtained from primary tumors and adjacent normal tissues. Coloreetal cancer is nearly asymptomatic at the early stages, which calls for development of fast and sensitive methods for molecular diagnostics. Proteomes of 11 paired specimens of primary colorectal tumors and adjacent histologically normal tissues were studied using comparative 2D PAGE. Altogether, 16 proteins with altered expression levels were detected, including 13 proteins with increased levels and three proteins with decreased levels in tumor tissues. These proteins were identified using MALDI-TOF mass spectrometry. The proteins GPD1, RRBP1 (increased levels), HNRNPH1, and SERPINB6 (decreased levels) have been associated with colorectal cancer for the first time.