2018年第一周小麦文献推荐（1.7）

本期作者 麦萌  小麦生信联盟

Hi,大家好！欢迎来到一周一次的小麦文献推荐。今天是2018年的第一次推荐，在此有必要对此简单的介绍下。首先，我们周一至周六会解读一些文献，但是限于我们主编的背景知识，在选择文献上可能具有一定的偏好性，再加上现在小麦研究越来越热门，发表的文章也会越来越多，研究的质量也会越来越高，所以总是会漏掉一些文献，这些漏掉的文献不代表不重要。为了弥补这个遗憾，我们特别在周末汇总这一周和小麦相关的文献，供大家浏览和参考，这些文献有些可能会被我们解读，有些则不会。每一篇文献会有题目，作者，发表杂志以及摘要信息，供大家决定是否需要进一步阅读。

想要特别声明一点，无论是我们推荐的文章还是我们做过导读的文章，都不能代替您亲自读文章，不能代表您对这篇文章的思考。同样一篇文献，每个人get到的点一定不一样。一个人多次阅读文章，可能每次引起的思考也会不同。

突然想起来颜宁说过她在国外上课时，老师都会给一些经典的生物文献，并且要求找出文献的问题。这种训练教会她学会质疑。科学没有挑战权威的质疑精神，就不可能有创新。同样的，这种讨论也应该存在于导师指导过程中，学生也要敢于向导师说出自己的想法，也许会由于思虑不周或欠缺相关背景知识而显得幼稚，或者观点错误，这些都没关系，立即改正过来就行。当然了，实际情况可能要复杂，导师也不是你想要和他讨论他就能和你讨论的。导师也是一个普通人，每个人都有自己的风格。

说的多了，我们正式开始我们的文献推荐。

1 Genetic diversity and virulence of wheat and barley strains of Xanthomonas translucens from the Upper Midwestern United States

Bacterial leaf streak (BLS) of wheat and barley, caused by Xanthomonas translucens pv. undulosa and Xanthomonas translucens pv. translucens, has been of growing concern in small grains production in the Upper Midwestern United States. To optimize disease resistance breeding, a greater awareness is needed of the pathovars and genetic diversity within the pathogens causing BLS in the region. Multilocus sequencing typing (MLST) and analysis (MLSA) of four common housekeeping genes (rpoD, dnaK, fyuA and gyrB) was used to evaluate the genetic diversity of 82 strains of X. translucens isolated between 2006 and 2013 from wheat, barley, rye and intermediate wheatgrass. In addition, in planta disease assays were conducted on 75 strains to measure relative virulence in wheat and barley. All strains were determined by MLSA to be related to X. translucens pv. undulosa and X. translucens pv. translucens. Clustering of strains based on Bayesian, network, and minimum spanning trees correlated with relative virulence levels in inoculated wheat and barley. Thus, phylogeny based on rpoD, dnaK, fyuA and gyrB correlated with host of isolation and was an effective means for predicting virulence of strains belonging to X. translucens pv. translucens and X. translucens pv. undulosa.

2 Analysis of contributors to grain yield in wheat at the individual quantitative trait locus level

In wheat, strong genetic correlations have been found between grain yield (GY) and tiller number per plant (TN), fertile spikelet number per spike (FSN), kernel number per spike (KN) and thousand-kernel weight (TKW). To investigate their genetic relationships at the individual quantitative trait locus (QTL) level, we performed both normal and multivariate conditional QTL analysis based on two recombinant inbred lines (RILs) populations. A total of 79 and 48 normal QTLs were identified in the International Triticeae Mapping Initiative (ITMI)/SHW-L1 9 Chuanmai 32 (SC) populations, respectively, as well as 55 and 35 conditional QTLs. Thirty-two QTL clusters in the ITMI population and 18 QTL clusters in the SC population explained 0.9%– 46.2% of phenotypic variance for two to eight traits. A comparison between the normal and conditional QTL mapping analyses indicated that FSN made the smallest contribution to GY among the four GY components that were considered at the QTL level. The effects of TN, KN and TKW on GY were stronger at the QTL level.

3 Genome-Wide Association Mapping of Loci for Resistance to Stripe Rust in North American Elite Spring Wheat Germplasm

Stripe rust, caused by Puccinia striiformis f. sp. tritici, is a major yield-limiting foliar disease of wheat (Triticum aestivum) worldwide. In this study, the genetic variability of elite spring wheat germplasm from North America was investigated to characterize the genetic basis of effective all-stage and adult plant resistance (APR) to stripe rust. A genome-wide association study was conducted using 237 elite spring wheat lines genotyped with an Illumina Infinium 90K single-nucleotide polymorphism array. All-stage resistance was evaluated at seedling stage in controlled conditions and field evaluations were conducted under natural disease pressure in eight environments across Washington State. High heritability estimates and correlations between infection type and severity were observed. Ten loci for race-specific all-stage resistance were confirmed from previous mapping studies. Three potentially new loci associated with race-specific all-stage resistance were identified on chromosomes 1D, 2A, and 5A. For APR, 11 highly significant quantitative trait loci (QTL) (false discovery rate < 0.01) were identified, of which 3 QTL on chromosomes 3A, 5D, and 7A are reported for the first time. The QTL identified in this study can be used to enrich the current gene pool and improve the diversity of resistance to stripe rust disease.

4 Fluorescence in situ hybridization karyotyping reveals the presence of two distinct genomes in the taxon Aegilops tauschii

The distribution of sites hybridizing to the two probes oligo-pTa-535 and (CTT)10 split the Ae. tauschii accessions into two clades, designated Dt and Ds, which corresponded perfectly with a previously assembled phylogeny based on marker genotype. The Dt cluster was populated exclusively by ssp. tauschii accessions, while the Ds cluster harbored both ssp. strangulata and morphologically intermediate accessions. As a result, it is proposed that Ae. tauschii ssp. tauschii is restricted to carriers of the Dt karyotype: their spikelets are regularly spaced along the rachis, at least in the central portion of their spike. Accessions classified as Ae. tauschii ssp. strangulata carry the Ds karyotype; their spikelets are irregularly spaced. Based on this criterion, forms formerly classified as ssp. tauschii var. meyeri have been re-designated ssp. strangulata var. meyeri.

According to the reworking of the taxon, the bread wheat D genome was most probably donated by ssp. strangulatavar. meyeri. Chromosomal differentiation reveals intra-species taxon of Ae. tauschii. Ae. tauschii ssp. tauschii has more distant relationship with breed wheat than ssp. strangulata and can be used for breeding improving effectively.

5 Asymmetrical changes of gene expression, small RNAs and chromatin in two resynthesized wheat allotetraploids

Polyploidy occurs in some animals and all flowering plants including important crops such as wheat. The consequences of polyploidy on crops remain elusive partly because their progenitors are unknown. Using two resynthesized wheat allotetraploids SlSlAA and AADD with known diploid progenitors, we analyzed mRNA and small RNA transcriptomes in the endosperm, compared transcriptomes between endosperm and root in AADD, and examined chromatin changes in the allotetraploids. In the endosperm, there were more nonadditively expressed genes in SlSlAA than in AADD. In AADD, nonadditively expressed genes were developmentally regulated, and the majority (62-70%) were repressed. The repressed genes in AADD included a group of histone methyltransferase gene homologs, which correlated with reduced histone H3K9me2 levels and activation of various transposable elements in AADD. In SlSlAA, there was a tendency of expression dominance of Sl over A homoeologs, but the histone methyltransferase gene homologs were additively expressed, correlating with insignificant changes in histone H3K9me2 levels. Moreover, more 24-nt small inferring RNAs (siRNAs) in the A subgenome were disrupted in AADD than in SlSlAA, which were associated with expression changes of siRNA-associated genes. Our results indicate that asymmetrical changes in siRNAs, chromatin modifications, transposons, and gene expression coincide with unstable AADD genomes and stable SlSlAA genomes, which could help explain evolutionary trajectories of wheat allotetraploids formed by different progenitors.

6 Genetic characterization of type II Fusarium head blight resistance derived from transgressive segregation in a cross between Eastern and Western Canadian spring wheat

Fusarium head blight (FHB) caused by Fusarium graminearum is a devastating disease affecting global wheat production, causing significant losses to yield and grain quality. The Eastern Canadian line FL62R1 was developed using a systemic breeding approach and boasts high levels of FHB resistance with good yield, desirable agronomics, and end-use quality traits. The objective of this study was to identify genetic determinants of type II resistance in a cross between FL62R1 and cv. Stettler, a Canada Western Red Spring variety rated moderately susceptible to FHB. Although neither parent displayed strong resistance to FHB spread within spikes following point inoculation (type II resistance) in greenhouses, strong type II resistance was observed in a large number of progeny, including 6% with resistance comparable to the best check line, Sumai 3. Quantitative trait locus (QTL) mapping identified a locus from chromosome 2BL of Stettler which provides Sumai 3 level type II resistance when combined with favorable FHB resistance QTLs with minor effects from FL62R1. This study provides insight into transgressive segregation for FHB, which despite its importance is poorly understood, rare, and difficult to predict. It also begins to dissect the genetic architecture of FHB resistance in wheat derived from the systemic breeding approach.

7 Brassinosteroids Modulate Meristem Fate and Differentiation of Unique Inflorescence Morphology in Setaria viridis(狗尾草,禾本科)

[发表在 The Plant Cell]

Inflorescence architecture is a key determinant of yield potential in many crops and is patterned by the organization and developmental fate of axillary meristems. In cereals, flowers and grain are borne from spikelets, which differentiate in the final iteration of axillary meristem branching. In Setaria spp., inflorescence branches terminate in either a spikelet or a sterile bristle, and these structures appear to be paired. In this work, we leverage Setaria viridis to investigate a role for the phytohormones brassinosteroids (BRs) in specifying bristle identity and maintaining spikelet meristem determinacy. We report the molecular identification and characterization of the Bristleless 1 (Bsl1) locus in S. viridis, which encodes a rate-limiting enzyme in BR biosynthesis. Loss-of-function bsl1 mutants fail to initiate a bristle identity program, resulting in homeotic conversion of bristles to spikelets. In addition, spikelet meristem determinacy is altered in the mutants, which produce two florets per spikelet instead of one. Both of these phenotypes provide avenues for enhanced grain production in cereal crops. Our results indicate that the spatiotemporal restriction of BR biosynthesis at boundary domains influences meristem fate decisions during inflorescence development. The bsl1 mutants provide insight into the molecular basis underlying morphological variation in inflorescence architecture.

8 Critical and speculative review of the roles of multi-protein complexes instarch biosynthesis in cereals

Starch accounts for the majority of edible carbohydrate resources generated through photosynthesis. Amylopectin is the major component of starch and is one of highest-molecular-weight biopolymers. Rapid and systematic synthesis of frequently branched hydro-insoluble amylopectin and efficient accumulation into amyloplasts of cereal endosperm is crucial. The functions of multiple starch biosynthetic enzymes, including elongation, branching, and debranching enzymes, must be temporally and spatially coordinated. Accordingly, direct evidence of protein-protein interactions of starch biosynthetic enzymes were first discovered in developing wheat endosperm in 2004, and they have since been shown in the developing seeds of other cereals. This review article describes structural characteristics of starches as well as similarities and differences in protein complex formation among different plant species and among mutant plants that are deficient in specific starch biosynthetic enzymes. In addition, evidence for protein complexes that are involved in the initiation stages of starch biosynthesis is summarized. Finally, we discuss the significance of protein complexes and describe new methods that may elucidate the mechanisms and roles of starch biosynthetic enzyme complexes.

9 Developmental responses of bread wheat to changes in ambient temperature following deletion of a locus that includes FLOWERING LOCUS T1

FLOWERING LOCUS T (FT) is a central integrator of environmental signals that regulates the timing of vegetative to reproductive transition in flowering plants. In model plants, these environmental signals have been shown to include photoperiod, vernalization and ambient temperature pathways, whilst in crop species the integration of the ambient temperature pathway remains less well understood. In hexaploid wheat, at least 5 FT-likegenes have been identified, each with a copy on the A, B and D genomes. Here we report the characterization of FT-B1 through analysis of FT-B1null and over-expression genotypes under different ambient temperature conditions. This analysis has identified that the FT-B1 alleles perform differently under diverse environmental conditions; most notably the FT-B1 null produces an increase in spikelet and tiller number when grown at lower temperature conditions. Additionally, absence of FT-B1facilitates more rapid germination under both light and dark conditions. These results provide an opportunity to understand the FT-dependent pathways that underpin key responses of wheat development to changes in ambient temperature. This is particularly important for wheat, for which development and grain productivity is sensitive to changes in temperature.

10 On the Origin of the Non-brittle Rachis Trait of Domesticated Einkorn Wheat

Einkorn and emmer wheat together with barley were among the first cereals domesticated by humans more than 10,000 years ago, long before durum or bread wheat originated. Domesticated einkorn wheat differs from its wild progenitor in basic morphological characters such as the grain dispersal system. This study identified the Non-brittle rachis 1 (btr1) and Non-brittle rachis 2 (btr2) in einkorn as homologous to barley. Re-sequencing of the Btr1 and Btr2in a collection of 53 lines showed that a single non-synonymous amino acid substitution (alanine to threonine) at position 119 at btr1, is responsible for the non-brittle rachis trait in domesticated einkorn. Tracing this haplotype variation back to wild einkorn samples provides further evidence that the einkorn progenitor came from the Northern Levant. We show that the geographical origin of domesticated haplotype coincides with the non-brittle domesticated barley haplotypes, which suggest the non-brittle rachis phenotypes of einkorn and barley were fixed in same geographic area in today’s South-east Turkey.

11 Pyramiding of transgenic Pm3 alleles in wheat results in improved powdery mildew resistance in the field

Allelic Pm3 resistance genes of wheat confer race-specific resistance to powdery mildew (Blumeria graminis f. sp. tritici, Bgt) and encode nucleotide-binding domain, leucine-rich repeat (NLR) receptors. Transgenic wheat lines overexpressing alleles Pm3a, b, c, d, f, and ghave previously been generated by transformation of cultivar Bobwhite and tested in field trials, revealing varying degrees of powdery mildew resistance conferred by the transgenes. Here, we tested four transgenic lines each carrying two pyramided Pm3 alleles, which were generated by crossbreeding of lines transformed with single Pm3 alleles. All four allele-pyramided lines showed strongly improved powdery mildew resistance in the field compared to their parental lines. The improved resistance results from the two effects of enhanced total transgene expression levels and allele-specificity combinations. In contrast to leaf segment tests on greenhouse-grown seedlings, no allelic suppression was observed in the field. Plant development and yield scores of the pyramided lines were similar to the mean scores of the corresponding parental lines, and thus, the allele pyramiding did not cause any negative effects. On the contrary, in pyramided line, Pm3b × Pm3f normal plant development was restored compared to the delayed development and reduced seed set of parental line Pm3f. Allele-specific RT qPCR revealed additive transgene expression levels of the two Pm3 alleles in the pyramided lines. A positive correlation between total transgene expression level and powdery mildew field resistance was observed. In summary, allele pyramiding of Pm3 transgenes proved to be successful in enhancing powdery mildew field resistance.

12 Chemical hybridizing agent SQ-1-induced male sterility in Triticum aestivum L.: a comparative analysis of the anther proteome

We performed proteomic analyses using the wheat Triticum aestivum L.to identify those proteins involved in physiological male sterility (PHYMS) induced by the chemical hybridizing agent CHA SQ-1. A total of 103 differentially expressed proteins were found by 2D–PAGE and subsequently identified by MALDI-TOF/TOF MS/MS. In general, these proteins had obvious functional tendencies implicated in carbohydrate metabolism, oxidative stress and resistance, protein metabolism, photosynthesis, and cytoskeleton and cell structure. In combination with phenotypic, tissue section, and bioinformatics analyses, the identified differentially expressed proteins revealed a complex network behind the regulation of PHYMS and pollen development. Accordingly, we constructed a protein network of male sterility in wheat, drawing relationships between the 103 differentially expressed proteins and their annotated biological pathways. To further validate our proposed protein network, we determined relevant physiological values and performed real-time PCR assays.

Our proteomics based approach has enabled us to identify certain tendencies in PHYMS anthers. Anomalies in carbohydrate metabolism and oxidative stress, together with premature tapetum degradation, may be the cause behind carbohydrate starvation and male sterility in CHA SQ-1 treated plants. Here, we provide important insight into the mechanisms underlying CHA SQ-1-induced male sterility. Our findings have practical implications for the application of hybrid breeding in wheat.

13 Effects of Three Parastagonospora nodorum Necrotrophic Effectors on Spring Wheat under Norwegian Field Conditions

The wheat (Triticum aestivum L.) disease Septoria nodorum blotch (SNB) is caused bythe necrotrophic fungus Parastagonospora nodorum (Berk.) Quaedvlieg, Verkley & Crousand causes significant yield and quality losses in several wheat growing regions. Theresistance mechanisms are quantitative and progress in resistance breeding has beenslow. However, gene-for-gene interactions involving necrotrophic effectors (NEs) andsensitivity genes (Snn) are involved, providing hope for more effective breeding. Althoughthe interactions are significant determinants of seedling SNB susceptibility, their role inadult plant leaf blotch resistance in the field is less understood. In this study, the frequencyof SnTox genes was investigated in 62 P.nodorum isolates collected in Norway. A panel of Norwegian and international spring wheat lines and cultivars was screened under natural SNB infection in a mist-irrigated field nurseryacross 7 yr. The lines were infiltrated in the greenhouse with the purified NEs SnToxA,SnTox1, and SnTox3, and the prevalence of corresponding sensitivity was investigated, aswell as correlation between NE sensitivity and resistance level in the field. The frequencies of SnToxA, SnTox1, and SnTox3 in the isolates were 0.69, 0.53 and 0.76, respectively.Sensitivity to SnToxA, SnTox1, and SnTox3 was present in 45, 12, and 55% of the plant material. Sensitivity to SnToxA was associated with significantly higher disease severity in the field than insensitivity. This indicates that elimination of SnToxA sensitivity in the breeding material by effector infiltrations or marker-assisted selection can be an effective way to increase field resistance to SNB.

14 Proteomic analysis of low-molecular-weight glutenin subunits and relationship with their genes in a common wheat variety

Although many studies on low-molecular-weight glutenin subunit (LMW-GS) function have been reported, a comprehensive comparison between specific genes and their protein product is still lacking. This study aimed to link the 43 genes isolated from the Korean wheat variety “Jokyoung” in the authors’ previous study to their protein products. Proteins were separated using two-dimensional gel electrophoresis (2-DGE) and identified by tandem mass spectrometry (MS/MS) at the gene haplotype level. Using MS/MS analysis of 17 protein spots, two spots were identified in the Glu-A3 locus and the corresponding haplotype was GluA3-13(Glu-A3c). Six spots were identified in the Glu-B3 locus and the corresponding haplotypes were GluB3-33 and GluB3-43 (Glu-B3h). Eight spots were identified in the Glu-D3 locus and the corresponding haplotypes were GluD3-11, GluD3-21, GluD3-31, GluD3-5, and GluD3-6 (Glu-D3a), and one spot was contaminated with gamma gliadin. Phylogenetic analysis and alignment of nucleotide and amino acid sequences assigned 35 of the 43 genes to seven haplotypes: GluA3-13, GluB3-43, GluD3-11, GluD3-21, GluD3-31, GluD3-42, and GluD3-5. Taken together, except for GluB3-33 and GluD3-6, which were not isolated, linking of each gene to the corresponding protein products at the gene haplotype level was accomplished using proteomic tools and phylogenetic analysis.

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