Characteristic expression of wheat PR5 gene in response to infection by the leaf rust pathogen,Puccinia triticina

TaLr35PR5 gene was obtained from the gDNA and cDNA of TcLr35 wheat. It was induced by Puccinia triticina, ABA and SA, but TaLr35PR5 was induced earlier and its expression level was higher in the incompatible interaction than that in the compatible interaction. In addition, the accumulations of TaLr35PR5 increased stably and showed significant peak challenged by P. triticina at different growth and development periods of TcLr35 wheat while it maintained similar level and changed little in mock inoculated. Western blottings were conducted to confirm that TaLr35PR5 be induced by P. triticina infection at the protein expression level. Similar to the expression patterns of TaLr35PR5 at RNA levels, the accumulations of TaLr35PR5 protein were weak in the seedling stage, then increased to the peak and kept constant levels at the mature stage which is consistent with the expression feature of Lr35 gene as an adult plant resistance gene.     

Genome‐wide association study reveals novel players in defense hormone crosstalk in Arabidopsis

Jasmonic acid (JA) regulates plant defenses against necrotrophic pathogens and insect herbivores. Salicylic acid (SA) and abscisic acid (ABA) can antagonize JA‐regulated defenses, thereby modulating pathogen or insect resistance. We performed a genome‐wide association (GWA) study on natural genetic variation in Arabidopsis thaliana for the effect of SA and ABA on the JA pathway. We treated 349 Arabidopsis accessions with methyl JA (MeJA), or a combination of MeJA and either SA or ABA, after which expression of the JA‐responsive marker gene PLANT DEFENSIN1.2 (PDF1.2) was quantified as a readout for GWA analysis. Both hormones antagonized MeJA‐induced PDF1.2 in the majority of the accessions but with a large variation in magnitude. GWA mapping of the SA‐ and ABA‐affected PDF1.2 expression data revealed loci associated with crosstalk. GLYI4 (encoding a glyoxalase) and ARR11 (encoding an Arabidopsis response regulator involved in cytokinin signalling) were confirmed by T‐DNA insertion mutant analysis to affect SA–JA crosstalk and resistance against the necrotroph Botrytis cinerea. In addition, At1g16310 (encoding a cation efflux family protein) was confirmed to affect ABA–JA crosstalk and susceptibility to Mamestra brassicae herbivory. Collectively, this GWA study identified novel players in JA hormone crosstalk with potential roles in the regulation of pathogen or insect resistance.     

Expression Profiles of Pathogenesis-Related Gene, <Emphasis Type="Italic">TaLr35PR1</Emphasis>, as it Relate to <Emphasis Type="Italic">Lr35</Emphasis>-Mediated Adult Plant Leaf Rust Resistance

Plants have developed sophisticated mechanisms to combat pathogen infection. One of the acquired modes in response to pathogen attack is the production of the pathogenesis-related (PR) proteins. Our earlier studies reported that TaLr35PR1, a PR1 gene encoding a protein with conserved serine carboxypeptidase (SCP) domain, has been cloned from wheat near-isogenic line TcLr35. However, the involvement of TaLr35PR1 in wheat growth and Lr35-mediated adult resistance to Puccinia triticina remains unclear. Here, we showed that TaLr35PR1 was strongly induced by P. triticina in wheat plant containing Lr35 (TcLr35), in which the expression level of TaLr35PR1 significantly increased and reached the maximum at 12 hpi. The accumulations of TaLr35PR1 increased stably and showed significant peak challenged by P. triticina at different growth and development periods of TcLr35 wheat while it maintained similar level and changed little in mock inoculated. Western blotting was conducted to confirm that TaLr35PR1 protein was increasingly accumulated in the TcLr35 adult plants after P. triticina inoculation and maintained at a similar level from 120 to 168 h post-inoculation. Similar to the expression patterns of TaLr35PR1 at RNA levels, the accumulations of TaLr35PR1 protein were weak in the seedling stage and then increased to the peak and kept constant levels at the mature stage which is consistent with the expression feature of Lr35 gene as an adult plant resistance gene. All these findings suggest that TaLr35PR1 is involved in wheat growth and Lr35-mediated adult wheat defense response to leaf rust pathogen attack.     

Identification of genes involved in stem rust resistance from wheat mutant D51 with the cDNA-AFLP technique

Wheat (Triticum aestivum L.) stem rust caused by Puccinia graminis f. sp. tritici is one of the main diseases of wheat worldwide. Wheat mutant line D51, which was derived from the highly susceptible cultivar L6239, shows resistance to the prevailing races 21C3CPH, 21C3CKH, and 21C3CTR of P. graminis f. sp. tritici in China. In this study, we used the cDNA-AFLP technology to identify the genes that are likely involved in the stem rust resistance. EcoRI/MseI selective primers were used to generate approximately 1920 DNA fragments. Seventy five differentially transcribed fragments (3.91%) were identified by comparing the samples of 21C3CPH infected D51 with infected L6239 or uninfected D51. Eleven amplified cDNA fragments were sequenced. Eight showed significant similarity to known genes, including TaLr1 (leaf rust resistance gene), wlm24 (wheat powdery mildew resistance gene), stress response genes and ESTs of environment stress of tall fescue. These identified genes are involved in plant defense response and stem rust resistance and need further research to determine their usefulness in breeding new resistance cultivars.     

The Lr34 adult plant rust resistance gene provides seedling resistance in durum wheat without senescence

The hexaploid wheat (Triticum aestivum) adult plant resistance gene, Lr34/Yr18/Sr57/Pm38/Ltn1, provides broad‐spectrum resistance to wheat leaf rust (Lr34), stripe rust (Yr18), stem rust (Sr57) and powdery mildew (Pm38) pathogens, and has remained effective in wheat crops for many decades. The partial resistance provided by this gene is only apparent in adult plants and not effective in field‐grown seedlings. Lr34 also causes leaf tip necrosis (Ltn1) in mature adult plant leaves when grown under field conditions. This D genome‐encoded bread wheat gene was transferred to tetraploid durum wheat (T. turgidum) cultivar Stewart by transformation. Transgenic durum lines were produced with elevated gene expression levels when compared with the endogenous hexaploid gene. Unlike nontransgenic hexaploid and durum control lines, these transgenic plants showed robust seedling resistance to pathogens causing wheat leaf rust, stripe rust and powdery mildew disease. The effectiveness of seedling resistance against each pathogen correlated with the level of transgene expression. No evidence of accelerated leaf necrosis or up‐regulation of senescence gene markers was apparent in these seedlings, suggesting senescence is not required for Lr34 resistance, although leaf tip necrosis occurred in mature plant flag leaves. Several abiotic stress‐response genes were up‐regulated in these seedlings in the absence of rust infection as previously observed in adult plant flag leaves of hexaploid wheat. Increasing day length significantly increased Lr34 seedling resistance. These data demonstrate that expression of a highly durable, broad‐spectrum adult plant resistance gene can be modified to provide seedling resistance in durum wheat.     

Molecular characterization of durum and common wheat recombinant lines carrying leaf rust resistance (Lr19) and yellow pigment (Y) genes from Lophopyrum ponticum

Chromosome 7E from Lophopyrum ponticum carries a valuable leaf rust resistant gene designated Lr19. This gene has not been widely used in common wheat breeding because of linkage with the yellow pigment gene Y. This gene tints flour yellow, reducing its appeal in bread making. However, a high level of yellow pigment is desirable in durum wheat breeding. We produced 97 recombinant chromosomes between L. ponticum transfer 7D.7E#1 and its wheat homoeologues, using the ph1b mutation that promotes homoeologous pairing. We characterized a subset of 37 of these lines with 11 molecular markers and evaluated their resistance to leaf rust and the abundance of yellow pigment. The Lr19 gene was mapped between loci Xwg420 and Xmwg2062, whereas Y was mapped distal to Xpsr687, the most distal marker on the long arm of chromosome 7. A short terminal 7EL segment translocated to 7A, including Lr19 and Y (line 1-23), has been transferred to durum wheat by backcrossing. The presence of this alien segment significantly increased the abundance of yellow pigment. The Lr19 also conferred resistance to a new durum leaf rust race from California and Mexico that is virulent on most durum wheat cultivars. The new durum lines with the recombinant 7E segment will be useful parents to increase yellow pigment and leaf rust resistance in durum wheat breeding programs. For the common wheat breeding programs, we selected the recombinant line 1-96, which has an interstitial 7E segment carrying Lr19 but not Y. This recombinant line can be used to improve leaf rust resistance without affecting flour color. The 7EL/7DL 1-96 recombinant chromosome did not show the meiotic self-elimination previously reported for a 7EL/7BL translocation.     

A wheat COP9 subunit 5‐like gene is negatively involved in host response to leaf rust

The COP9 (constitutive photomorphogenesis 9) signalosome (CSN) is a protein complex involved in the ubiquitin proteasome system and a common host target of diverse pathogens in Arabidopsis. The known derubylation function of the COP9 complex is carried out by subunit 5 encoded by AtCSN5A or AtCSN5B in Arabidopsis. A single CSN5‐like gene (designated as TaCSN5) with three homeologues was identified on the long arms of wheat (Triticum aestivum L.) group 2 chromosomes. In this study, we identified and characterized the function of TaCSN5 in response to infection by the leaf rust pathogen. Down‐regulation of all three TaCSN5 homeologues or mutations in the homeologues on chromosomes 2A or 2D resulted in significantly enhanced resistance to leaf rust. Enhanced leaf rust resistance corresponded to a seven‐fold increase in PR1 (pathogenesis‐related gene 1) expression. Collectively, the data indicate that the wheat COP9 subunit 5‐like gene acts as a negative regulator of wheat leaf rust resistance.     

Effect of salicylic acid and methyl jasmonate on phenylalanine ammonia-lyase activity and total phenol in wheat infected by Pratylenchus thornei

The effect of biochemical responses in wheat seedlings cultivar Falat against lesion nematode (Pratylenchus thornei) was investigated by two factors inducer resistance salicylic acid (SA) and methyl jasmonate (MeJA). Foliar sprays with 1?ml SA 1?mM and 1?ml MeJA 100?μM was conducted on 20-day-old wheat (cv. Falat) seedlings. About 24?h after foliar sprays, plants were inoculated by root lesion nematode. Phenylalanine ammonia-lyase (PAL) activity was increased significantly in all treatments two days after inoculation over control. However, PAL activity was decreased in all treatments five days after inoculation in compared to control. What is more, in both time points, total phenol increased in all treatments over control. The comparison of both inducers SA and MeJA on total phenol in healthy and infected wheat seedlings in both days two and five after inoculation of nematode indicated that total phenol has decreased significantly in all treatments in the fifth day.     

Jasmonic Acid and Salicylic Acid Induce Accumulation of β-1,3-Glucanase and Thaumatin-Like Proteins in Wheat and Enhance Resistance Against Stagonospora nodorum

The effect of application of jasmonic acid (JA) and salicylic acid (SA) on the induction of resistance in wheat to Stagonospora nodorum and on the induction of -1,3-glucanase and thaumatin-like proteins (TLPs) was studied. Western blot analysis revealed that two -1,3-glucanases with apparent molecular masses of 31 and 33 kDa that cross-reacted with a barley glucanase antiserum were induced in wheat leaves after treatment with JA and SA. When wheat plants were treated with SA and JA, a TLP with an apparent molecular mass of 25 kDa and several other isoforms of TLP were induced. Pre-treatment of wheat plants with SA and JA significantly reduced (up to 56 %) the incidence of leaf blotch disease incited by S. nodorum compared with untreated control plants.     

Jasmonate- and salicylate-induced defenses in wheat affect host preference and probing behavior but not performance of the grain aphid,Sitobion avenae

Jasmonate and salicylatemediated signaling pathways play significant roles in induced plant defenses, but there is no sufficient evidence for their roles in monocots against aphids. We exogenously applied methyl jasmonate （MeJA） and salicylic acid （SA） on wheat seedlings and examined biochemical responses in wheat and effects on the grain aphid, Sitobion avenae （Fab.）. Application of MeJA significantly increased levels of wheat＇s polyphenol oxidase, peroxidase and proteinase inhibitor 1, 2 and 6 days after treatment. In twochoice tests, adult aphids preferred control wheat leaves to MeJA or SA treated leaves. Electrical penetration graph （EPG） recordings of aphid probing behavior revealed that on MeJAtreated plants, the duration of aphid＇s first probe was significantly shorter and number of probes was significantly higher than those on control plants. Also total duration of probing on MeJAtreated plants was significantly shorter than on control plants. Total duration of salivation period on SAtreated plants was significantly longer, while mean phloem ingestion period was significantly shorter than on control plants. However, no significant difference in total duration of phloem sap ingestion period was observed among treatments. The EPG data suggest that MeJAdependent resistance factors might be due to feeding deterrents in mesophyll, whereas the SAmediated resistance may be phloembased. We did not observe any significant difference of MeJA and SA application on aphid development, daily fecundity, intrinsic growth rate and population growth. The results indicate that both MeJA and SAinduced defenses in wheat deterred S. avenae colonization processes and feeding behavior, but had no significant effects on its performance.     

水稻NAM基因家族的全基因组鉴定及表达分析

植物特异性转录因子NAM家族从属于NAC转录因子超家族,在植株生长发育、生理代谢以及应对各种胁迫反应中均发挥重要作用。该研究采用生物信息学方法鉴定水稻基因组中的NAM基因,分析其时空表达模式、亚细胞定位以及蛋白相互作用,并采用实时定量qRT PCR方法分析不同外源激素(如SA、ABA和MeJA)以及非生物胁迫(包括干旱、盐和冷)处理下各NAM基因的表达特征,为进一步探索NAM基因在非生物胁迫中的功能和应激机制以及激素调控途径奠定基础。结果显示：(1)从水稻基因组中共鉴定出48个NAM基因,进化分析将其分为5个亚家族;NAM基因在水稻基因组中存在9对片段复制事件。(2)组织表达分析显示,NAM基因在水稻不同组织及发育时期表现特异性表达,特别是叶鞘、茎和节的生长过程中高表达,且大多数是核定位,并存在多种蛋白互作。(3)实时定量qRT PCR表达分析显示,10个NAM基因在不同组织中均特异表达;大部分NAM基因在盐和干旱胁迫下表达上调,而在冷胁迫下表达降低;SA、ABA和MeJA处理均可显著改变各NAM基因的表达水平。研究表明,NAM基因在水稻生长发育、激素应答和非生物胁迫响应中具有重要作用。     

Dr. Heinz rogoll‐70 Jahre

The wheat crop remains vulnerable to all three rust diseases (leaf rust, stem rust and yellow rust) caused by Puccinia spp. according to the prevalence of the pathogen in different wheat-growing areas worldwide. Stripe rust or yellow rust caused by Puccinia striiformis f. sp. tritici is the most significant rust pathogen which prefers cool, moist areas and highlands. The pathogen is recognised as responsible for huge production losses in wheat. Genetic variation in pathogen makes its control difficult. Therefore, resistance against all the races of the pathogen known as durable or race-non-specific resistance is preferred. The present study was carried out to identify durable resistance against stripe rust in selected wheat cultivars from Pakistan through seedling testing, field evaluation at adult stage, morphological marker studies and marker-assisted selection. Results revealed that 4% of the cultivars were resistant at the seedling stage while the rest were susceptible or intermediate. To confirm their field resistance, the same cultivars were evaluated under field conditions at Cereal Crops Research Institute Pirsabak (located in Khyber Pakhtunkhwa, KP) a hot spot of stripe rust in Pakistan. Observations exhibited that at the adult stage 4% of the cultivars were resistant, 70% intermediate or moderately resistant while the others were highly susceptible. Leaf tip necrosis was observed in 30% of the cultivars. Wheat cultivars showing susceptibility at the seedling stage were highly to moderately resistant at adult stage showing durable resistance. For further validation, morphological markers were also observed in cultivars indicating the presence of Yr18/Lr34 gene. Eleven cultivars (C-518, Mexipak, Kohinoor-83, Faisalabad-83, Zardana-93, Shahkar-95, Moomal-2002, Wattan-94, Pasban-90, Kiran-95, and Haider-2000) were identified, having durable or race non-specific resistance against stripe rust. These cultivars can further be utilised in wheat breeding programmes for deploying durable resistance to attain long lasting control against stripe rust.     

小麦隐匿柄锈菌与小麦互作不同阶段的基因差异表达分析

[目的]小麦叶锈病是影响小麦生产主要病害之一,其病原菌新小种的出现和劣势小种上升为优势小种导致抗病品种的抗病性不断被克服.小麦隐匿柄锈菌与小麦互作不同阶段差异表达谱分析对于揭示该病菌致病的分子机制,进而有效防控小麦叶锈病具有重要意义.[方法]利用转录组分析小麦隐匿柄锈菌致病生理小种与感叶锈病小麦品种MuTcLr19亲和...