Mapping of powdery mildew resistance genes transferred to common wheat from wild emmer wheat revealed three functional Pm60 haplotypes

Powdery mildew(PM),caused by Blumeria graminis f.sp.tritici(Bgt),is one of the destructive wheat diseases worldwide.Wild emmer wheat(Triticum turgidum ssp.dicoccoides,WEW),a tetraploid progenitor of common wheat,is a valuable genetic resource for wheat disease resistance breeding programs.We developed three hexaploid pre-breeding lines with PM resistance genes derived from three WEW accessions.These resistant pre-breeding lines were crossed with susceptible common wheat accessions.Segregations in the F2populations were 3 resistant:1 susceptible,suggesting a single dominant allele in each resistant parent.Mapping of the resistance gene in each line indicated a single locus on the long arm of chromosome 7A,at the approximate location of previously cloned Pm60 from T.urartu.Sanger sequencing revealed three different Pm60 haplotypes(Hap 3,Hap 5,and Hap 6).Co-segregating diagnostic markers were developed for identification and selection of each haplotype.The resistance function of each haplotype was verified by the virus-induced gene silencing(VIGS).Common wheat lines carrying each of these Pm60 haplotypes were resistant to most Bgt isolates and differences in the response arrays suggested allelic variation in response.

Changes in concentrations and transcripts of plant hormones in wheat seedling roots in response to Fusarium crown rot

Fusarium crown rot(FCR) is a soilborne disease causing severe yield losses in many wheat-growing areas of the world. Diseased plants show browning and necrosis of roots and stems causing white heads at maturity. Little is known about the molecular processes employed by wheat roots to respond to the disease. We characterized morphological, transcriptional and hormonal changes in wheat seedling roots following challenge with Fusarium pseudograminearum(Fp), the main pathogen of FCR. The pathogen inhibited root development to various extents depending on plants' resistance level. Many genes responsive to FCR infection in wheat roots were enriched in plant hormone pathways. The contents of compounds involved in biosynthesis and metabolism of jasmonic acid, salicylic acid, cytokinin and auxin were drastically changed in roots at five days post-inoculation. Presoaking seeds in methyl jasmonate for 24 h promoted FCR resistance, whereas presoaking with cytokinin 6-benzylaminopurine made plants more susceptible. Overexpression of TaOPR3, a gene involved in jasmonic acid biosynthesis, enhanced plant resistance as well as root and shoot growth during infection.

Copy number variation of B1 controls awn length in wheat

Wheat awns contribute to photosynthesis and grain production.In this study,an F2population and F2:3families from a cross between the awned line 7D12 and the Chinese awnless variety Shiyou 20(SY20)were used to identify loci associated with awn length.Bulked-segregant RNA sequencing and linkage mapping identified a single dominant locus in a 0.3 cM interval on chromosome 5AL.Five genes were in the interval,including the recently cloned awn inhibitor B1.Although a single copy of the B1 gene was detected in 7D12,SY20 carried five copies of the gene.Increased copy number of B1 in SY20enhanced gene expression.Based on sequence variation among the promoter regions of five B1 gene copies in SY20,two dominant markers were developed and found to cosegregate with B1 in a population of 931 wheat accessions.All 77 awnless accessions harbored sequence variations in the B1 promoter regions similar to those of SY20 and thus carried multiple copies of the gene,whereas 15 randomly selected awned wheats carried only one copy.These results suggest that an increase in copy number of the B1 gene is associated with inhibition of awn length.

超声波表征天然橡胶/环氧化天然橡胶并用体系的硫化过程

在料腔安装超声波探头的无转子硫化仪上同步监测天然橡胶(NR)/环氧化天然橡胶(ENR)硫化过程得到了声速曲线和扭矩曲线,对比其相似性提出了超声波表征硫化历程的方法,指出其对微观结构和密实度变化更加灵敏。在压力-体积-温度(PVT)-超声波检测装置上同步测试了该并用胶的比容和声速,这两种同步测试数据可用直线方程、考虑压力效应的声阻抗方程和从Tait方程推导直接反映温度效应的方程对硫化过程进行较好描述,说明超声波还可直接监测硫化胶的比容变化。

Identifying changes in the wheat kernel proteome under heat stress using iTRAQ

Wheat(Triticum aestivum L.) is one of the three major global food crops. Hightemperature stress can affect its yield and quality. Studies of the effect of hightemperature stress on wheat kernel development are important because they can reveal the stability of wheat quality and lead to the genetic improvement of wheat quality traits. In this study, the isobaric tags for relative and absolute quantitation(iTRAQ)method was adopted to analyze changes in the protein expression profile of wheat cultivars under high temperature stress. The protein content of wheat grain increased under heat stress, while the SDS-sedimentation value and starch content decreased.Grain filling was deficient under high temperature stress, which reduced thousandkernel weight but did not affect wheat kernel length. The 207 differentially expressed proteins identified in Gaocheng 8901 under heat stress were associated with energy metabolism, growth and development, and stress response. Gene Ontology enrichment analysis showed that the annotated proteins that were differentially expressed in Gaocheng 8901 under heat stress were involved mainly in stimulus response, abiotic stress response, stress response, and plasma membrane. A set of 78 differentially expressed proteins were assigned to 83 KEGG signaling/metabolic pathways. KEGG pathway enrichment analysis showed that this set of proteins was significantly enriched in members of 51 pathways, and the proteins participated mainly in protein synthesis in the endoplasmic reticulum, starch and sucrose metabolism, and reaction on ribosomes. Five differentially expressed proteins were involved in protein–protein interaction networks that may greatly influence the yield and quality of wheat grain. In wheat, high-temperature stress leads to a variety of effects on protein expression and may ultimately cause changes in yield and quality.

Integrated transcriptome and metabolite profiling highlights the role of benzoxazinoids in wheat resistance against Fusarium crown rot

Fusarium crown rot(FCR), caused by Fusarium spp., is a chronic and severe plant disease worldwide. In the last years, the incidence and severity of FCR in China has increased to the point that it is now considered a threat to local wheat crops. In this study, for the first time, the metabolites and transcripts responsive to FCR infection in the partial resistant wheat cultivar 04 Zhong 36(04 z36) and susceptible cultivar Xinmai 26(XM) were investigated and compared at 20 and 25 days post inoculation(dpi). A total of 443 metabolites were detected, of which 102 were significantly changed because of pathogen colonization.Most of these 102 metabolites belonged to the flavonoid, phenolic acid, amino acid and derivative classes.Some metabolites, such as proline betaine, lauric acid, ribitol, and arabitol, were stably induced by Fusarium pseudograminearum(Fp) infection at two time points and may have important roles in FCR resistance. In line with the reduced seedling height of 04 z36 and XM plants, RNA-seq analysis revealed that FCR infection significantly affected the photosynthesis activities in two cultivars. Furthermore, 15 jasmonate ZIM-domain genes(JAZ) in the significantly enriched ‘regulation of jasmonic acid mediated signaling pathway’ in 04 z36 were down-regulated. The down-regulation of these JAZ genes in 04 z36 may cause a strong activation of the jasmonate signaling pathway. Based on combined data from gene expression and metabolite profiles, two metabolites, benzoxazolin-2-one(BOA) and 6-methoxy-benzoxazolin-2-one(MBOA), involved in the benzoxazinoid-biosynthesis pathway, were tested for their effects on FCR resistance. Both BOA and MBOA significantly reduced fungal growth in vitro and in vivo, and, thus, a higher content of BOA and MBOA in 04 z36 may contribute to FCR resistance. Above all, the current analysis extends our understanding of the molecular mechanisms of FCR resistance/susceptibility in wheat and will benefit further efforts for the genetic improvement of disease resistance.

TaMADS29 interacts with TaNF-YB1 to synergistically regulate early grain development in bread wheat

Grain development is a crucial determinant of yield and quality in bread wheat(Triticum aestivum L.).However,the regulatory mechanisms underlying wheat grain development remain elusive.Here we report how Ta MADS29 interacts with Ta NF-YB1 to synergistically regulate early grain development in bread wheat.The tamads29 mutants generated by CRISPR/Cas9 exhibited severe grain filling deficiency,coupled with excessive accumulation of reactive oxygen species(ROS)and abnormal programmed cell death that occurred in early developing grains,while overexpression of Ta MADS29 increased grain width and1,000-kernel weight.Further analysis revealed that Ta MADS29 interacted directly with Ta NF-YB1;null mutation in Ta NF-YB1caused grain developmental deficiency similar to tamads29 mutants.The regulatory complex composed of Ta MADS29 and Ta NF-YB1 exercises its possible function that inhibits the excessive accumulation of ROS by regulating the genes involved in chloroplast development and photosynthesis in early developing wheat grains and prevents nucellar projection degradation and endosperm cell death,facilitating transportation of nutrients into the endosperm and wholly filling of developing grains.Collectively,our work not only discloses the molecular mechanism of MADS-box and NF-Y TFs in facilitating bread wheat grain development,but also indicates that caryopsis chloroplast might be a central regulator of grain development rather than merely a photosynthesis organelle.More importantly,our work offers an innovative way to breed high-yield wheat cultivars by controlling the ROS level in developing grains.

Suppression of ZEAXANTHIN EPOXIDASE 1 restricts stripe rust growth in wheat

Reducing losses caused by pathogens is an effective strategy for stabilizing crop yields.Daunting challenges remain in cloning and characterizing genes that inhibit stripe rust,a devastating disease of wheat(Triticum aestivum)caused by Puccinia striiformis f.sp.tritici(Pst).We found that suppression of wheat zeaxanthin epoxidase 1(ZEP1)increased wheat defense against Pst.We isolated the yellow rust slower 1(yrs1)mutant of tetraploid wheat in which a premature stop mutation in ZEP1-B underpins the phenotype.Genetic analyses revealed increased H_(2)O_(2) accumulation in zep1 mutants and demonstrated a correlation between ZEP1 dysfunction and slower Pst growth in wheat.Moreover,wheat kinase START 1.1(WKS1.1,Yr36)bound,phosphorylated,and suppressed the biochemical activity of ZEP1.A rare natural allele in the hexaploid wheat ZEP1-B promoter reduced its transcription and Pst growth.Our study thus identified a novel suppressor of Pst,characterized its mechanism of action,and revealed beneficial variants for wheat disease control.This work opens the door to stacking wheat ZEP1 variants with other known Pst resistance genes in future breeding programs to enhance wheat tolerance to pathogens.

Transcriptome Comparison of Susceptible and Resistant Wheat in Response to Powdery Mildew Infection

Powdery mildew （Pro） caused by the infection of Blumeria graminis f. sp. tritici （Bgt） is a worldwide crop disease resulting in significant loss of wheat yield. To profile the genes and pathways responding to the Bgt infection, here, using Affymetrix wheat microarrays, we compared the leaf transcriptomes before and after Bgt inoculation in two wheat genotypes, a Pm-susceptible cultivar Jingdong 8 （S） and its near-isogenic line （R） carrying a single Pm resistant gene Pm30. Our analysis showed that the original gene expression status in the S and R genotypes of wheat was almost identical before Bgt inoculation, since only 60 genes exhibited differential expression by P = 0.01 cutoff. However, 12 h after Bgt inoculation, 3014 and 2800 genes in the S and R genotype, respectively, responded to infec- tion. A wide range of pathways were involved, including cell wall fortification, flavonoid biosynthesis and metabolic processes. Further- more, for the first time, we show that sense-antisense pair genes might be participants in wheat-powdery mildew interaction. In addition, the results of qRT-PCR analysis on several candidate genes were consistent with the microarray data in their expression patterns. In summary, this study reveals leaf transcriptome changes before and after powdery mildew infection in wheat near-isogenic lines, suggest- ing that powdery mildew resistance is a highly complex systematic response involving a large amount of gene regulation.

Synergistic modification of the tribological properties of polytetrafluoroethylene with polyimide and boron nitride

Polytetrafluoroethylene(PTFE)blended with polyimide(PI)and filled with boron nitride(BN)is prepared through cold pressing and sintering for composites with remarkable wear resistance and reduced coefficient of friction(COF).The characterizations show that BN and PI at different levels,improve the hardness,dynamic thermo-mechanical modulus,thermal conductivity,and tribological properties of PTFE.PI boosts the dispersion and bonding of BN in PTFE.In dry sliding friction of a block-on-ring tribometer,the wear rate and COF of 10:10:80 BN/PI/PTFE reduce to almost 1/300 and 80%of those of pure PTFE,respectively,as the wear mechanism transition from being adhesive to partially abrasive.This occurs only when the additives BN and PI induce a synergistic effect,that is,at concentrations that are not higher than ca.10 wt%and 15 wt%,respectively.The obvious agglomeration at high percentages of added PI and severe conditions(400 N and 400 rpm)induce strong adhesive failure.The variations in the tensile properties,hardness,crystallization,and microstructure of the composites correspond to different effects.The multiple parameters of the plots of wear and friction are transformed into their contour curves.The mechanism transition maps aid in understanding the influence of various test conditions and composite compositions on the contact surfaces in the space-time framework of wear.