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Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici ( Pst ), is a global threat to wheat production. Aegilops tauschii , one of the wheat progenitors, carries the YrAS2388 locus for resistance to Pst on chromosome 4DS. We reveal that YrAS2388 encodes a typical nucleotide oligomerization domain-like receptor (NLR). The Pst -resistant allele YrAS2388R has duplicated 3’ untranslated regions and is characterized by alternative splicing in the nucleotide-binding domain. Mutation of the YrAS2388R allele disrupts its resistance to Pst in synthetic hexaploid wheat; transgenic plants with YrAS2388R show resistance to eleven Pst races in common wheat and one race of P . striiformis f. sp. hordei in barley. The YrAS2388R allele occurs only in Ae. tauschii and the Ae. tauschii -derived synthetic wheat; it is absent in 100% ( n  = 461) of common wheat lines tested. The cloning of YrAS2388R will facilitate breeding for stripe rust resistance in wheat and other Triticeae species. Stripe rust is a serious threat to wheat production. Here, the authors reveal that the resistance gene, only present in the wheat progenitor Aegilops tauschii and its derived synthetic wheat, encodes a nucleotide oligomerization domain-like receptor and confers resistance in common wheat and barley.

• Pre-harvest sprouting (PHS), the germination of grain before harvest, is a serious problem resulting in wheat yield and quality losses. • Here, we mapped the PHS resistance gene PHS-3D from synthetic hexaploid wheat to a 2.4 Mb presence–absence variation (PAV) region and found that its resistance effect was attributed to the pleiotropic Myb10-D by integrated omics and functional analyses. • Three haplotypes were detected in this PAV region among 262 worldwide wheat lines and 16 Aegilops tauschii, and the germination percentages of wheat lines containing Myb10-D was approximately 40% lower than that of the other lines. Transcriptome and metabolome profiling indicated that Myb10-D affected the transcription of genes in both the flavonoid and abscisic acid (ABA) biosynthesis pathways, which resulted in increases in flavonoids and ABA in transgenic wheat lines. Myb10-D activates 9-cis-epoxycarotenoid dioxygenase (NCED) by biding the secondary wall MYB-responsive element (SMRE) to promote ABA biosynthesis in early wheat seed development stages. • We revealed that the newly discovered function of Myb10-D confers PHS resistance by enhancing ABA biosynthesis to delay germination in wheat. The PAV harboring Myb10-D associated with grain color and PHS will be useful for understanding and selecting white grained PHS resistant wheat cultivars.

The MADS-box genes encode transcription factors with key roles in plant growth and development. A comprehensive analysis of the MADS-box gene family in bread wheat (Triticum aestivum) has not yet been conducted, and our understanding of their roles in stress is rather limited. Here, we report the identification and characterization of the MADS-box gene family in wheat. A total of 180 MADS-box genes classified as 32 Mα, 5 Mγ, 5 Mδ, and 138 MIKC types were identified. Evolutionary analysis of the orthologs among T. urartu, Aegilops tauschii and wheat as well as homeologous sequences analysis among the three sub-genomes in wheat revealed that gene loss and chromosomal rearrangements occurred during and/or after the origin of bread wheat. Forty wheat MADS-box genes that were expressed throughout the investigated tissues and development stages were identified. The genes that were regulated in response to both abiotic stresses (i.e., phosphorus deficiency, drought, heat, and combined drought and heat) and biotic stresses (i.e., Fusarium graminearum, Septoria tritici, stripe rust and powdery mildew) were detected as well. A few notable MADS-box genes were specifically expressed in a single tissue and those showed relatively higher expression differences between the stress and control treatment. The expression patterns of considerable MADS-box genes differed from those of their orthologs in Brachypodium, rice, and Arabidopsis. Collectively, the present study provides new insights into the possible roles of MADS-box genes in response to stresses and will be valuable for further functional studies of important candidate MADS-box genes.

Hexaploid wheat (Triticum aestivum, genomes AABBDD) originated by hybridization of tetraploid Triticum turgidum (genomes AABB) with Aegilops tauschii (genomes DD). Genetic relationships between A. tauschii and the wheat D genome are of central importance for the understanding of wheat origin and subsequent evolution. Genetic relationships among 477 A. tauschii and wheat accessions were studied with the A. tauschii 10K Infinium single nucleotide polymorphism (SNP) array. Aegilops tauschii consists of two lineages (designated 1 and 2) having little genetic contact. Each lineage consists of two closely related sublineages. A population within lineage 2 in the southwestern and southern Caspian appears to be the main source of the wheat D genome. Lineage 1 contributed as little as 0.8% of the wheat D genome. Triticum aestivum is subdivided into the western and Far Eastern populations. The Far Eastern population conserved the genetic make-up of the nascent T. aestivum more than the western population. In wheat, diversity is high in chromosomes 1D and 2D and it correlates in all wheat D-genome and A. tauschii chromosomes with recombination rates. Gene flow from A. tauschii was an important source of wheat genetic diversity and shaped its distribution along the D-genome chromosomes.

Key messageMajor and environmentally stable QTL for flag leaf-related traits in wheat were identified and validated across ten environments using six populations with different genetic backgrounds.Flag leaf size and posture are two important factors of “ideotype” in wheat. Despite numerous studies on genetic analysis of flag leaf size including flag leaf length (FLL), width (FLW), area (FLA) and the ratio of length/width (FLR), few have focused on flag leaf posture including flag leaf angle (FLANG), opening angle (FLOA) and bend angle (FLBA). Further, the numbers of major, environmentally stable and verified genetic loci for flag leaf-related traits are limited. In this study, QTL for FLL, FLW, FLA, FLR, FLANG, FLOA and FLBA were identified based on a recombinant inbred line population together with values from up to ten different environments. Totally, eight major and stably expressed QTL were identified. Three co-located chromosomal intervals for seven major QTL were identified. The five major QTL QFll.sicau-5B.3 and QFll.sicau-2D.3 for FLL, QFlr.sicau-5B for FLR, QFlw.sicau-2D for FLW and QFla.sicau-2D for FLA were successfully validated by the tightly linked Kompetitive Allele Specific PCR (KASP) markers in the other five populations with different genetic backgrounds. A few genes related to leaf growth and development in intervals for these major QTL were predicated. Significant relationships between flag leaf- and yield-related traits were evidenced by analyses of Pearson correlations, conditional QTL and genetic mapping. Taken together, these results provide valuable information for understanding flag leaf size and posture of “ideotype” as well as fine mapping and breeding utilization of promising loci in bread wheat.

Chloroplasts are key players in photosynthesis and immunity against microbial pathogens. However, the precise and timely regulatory mechanisms governing the control of photosynthesis-associated nuclear genes (PhANGs) expression in plant immunity remain largely unknown. Here we report that TaPIR1, a Pst -induced RING-finger E3 ubiquitin ligase, negatively regulates Pst resistance by specifically interacting with TaHRP1, an atypical transcription factor histidine-rich protein. TaPIR1 ubiquitinates the lysine residues K 131 and K 136 in TaHRP1 to regulate its stability. TaHRP1 directly binds to the TaHRP1-binding site elements within the PhANGs promoter to activate their transcription via the histidine-rich domain of TaHRP1. PhANGs expression induces the production of chloroplast-derived ROS. Although knocking out TaHRP1 reduces Pst resistance, TaHRP1 overexpression contributes to photosynthesis, and chloroplast-derived ROS production, and improves disease resistance. TaPIR1 expression inhibits the downstream activation of TaHRP1 and TaHRP1-induced ROS accumulation in chloroplasts. Overall, we show that the TaPIR1-mediated ubiquitination and degradation of TaHRP1 alters PhANGs expression to disrupt chloroplast function, thereby increasing plant susceptibility to Pst . Wheat E3 ubiquitin ligase TaPIR1-mediated ubiquitination and degradation of an atypical transcription factor TaHRP1 alters PhANGs expression to disrupt chloroplast function and ROS accumulation, increasing plant susceptibility to wheat stripe rust.

Background Starch, a major component of wheat ( Triticum aestivum L.) grain, plays a crucial role in determining processing quality. Granule-bound starch synthase I (GBSSI), the enzyme primarily responsible for elongating α-1,4-glucan chains into linear amylose molecules, is a key determinant of starch quality. In this study, a mutant population of the wheat cultivar SM126, a high-quality variety form Sichuan, China, was generated using ethyl methanesulfonate (EMS) mutagenesis. This research investigates the effects of GBSSI inactivation on starch structure and functionality. Results A waxy mutant (Wx-Abd) was identified by screening an M4 seed library with sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of grain endosperm flour. DNA sequencing revealed a single nucleotide polymorphism (SNP) in the fourth exon, causing a premature stop codon and inactivation of the Wx-Abd allele. In previous work, the Wx-abD mutant was identified in the M2 generation, and crossing the M2-31 line with the M4-6165 line produced four distinct Wx protein subunits in the SM126 background. Comparisons between the Wx-abd line and the wild-type SM126 (Wx-AbD) showed significant differences in starch properties. The Wx-abd line exhibited reduced Wx gene expression, a distinct surface depression on starch granules, and a higher proportion of B-type starch granules. Notably, it exhibited significantly lower amylose content (7.02%) compared to SM126 (22.32%), along with a reduction in total starch content. Additionally, the Wx-abd line showed a higher gelatinization temperature. Conclusion Inactivation of GBSSI in the Wx-abd line resulted in altered starch structure, particularly a decrease in amylose content and changes in granule morphology. These findings suggest that the Wx-abd line represents a valuable genetic resource for wheat breeding programs focused on improving starch quality for food production, with its high agronomic performance making it suitable for further breeding applications.

Powdery mildew, caused by the fungus f. sp. , represents a yield constraint in many parts of the world. Here, the introduction of a resistance gene carried by the cereal rye cv. Qinling chromosome 6R was transferred into wheat in the form of spontaneous balanced translocation induced in plants doubly monosomic for chromosomes 6R and 6A. The translocation, along with other structural variants, was detected using hybridization and genetic markers. The differential disease response of plants harboring various fragments of 6R indicated that a powdery mildew resistance gene(s) was present on both arms of rye chromosome 6R. Based on karyotyping, the short arm gene, designated , was mapped to the subtelomere region of the arm. The Robertsonian translocation 6AL⋅6RS can be exploited by wheat breeders as a novel resistance resource.

Phytopathogens such as Puccinia striiformis f. sp. tritici ( Pst ) induce pigment retention at pathogen infection sites. Although pigment retention is commonly observed in diverse pathosystems, its underlying physiological mechanism remains largely unclear. Herein, we identify and characterize a wheat leaf senescence gene, TaSGR1 , which enhances resistance against Pst by promoting leaf senescence and H 2 O 2 accumulation while inhibiting photosynthesis. Knockout of TaSGR1 (STAYGREEN) in wheat increases pigment retention and plant susceptibility. Pst_TTP1 (TaTrx-Targeting Protein 1), a secreted rust fungal effector critical for Pst virulence, binds to the plastidial thioredoxin TaTrx (Thioredoxin), preventing its translocation into chloroplasts. Within the chloroplasts, TaTrx catalyzes the transformation of TaSGR1 oligomers into monomers. These TaSGR1 monomers accumulate in the chloroplasts, accelerating leaf senescence, H 2 O 2 accumulation, and cell death. The inhibition of this oligomer-to-monomer transformation, caused by the failure of TaTrx to enter the chloroplast due to Pst_TTP1, impairs plant resistance against Pst . Overall, our study reveals the suppression of redox signaling cascade that catalyzes the transformation of TaSGR1 oligomers into monomers within chloroplasts and the inhibition of leaf chlorosis by rust effectors as key mechanisms underlying disease susceptibility. One effector of wheat disease pathogen is found to prevent the entry of thioredoxin into chloroplast. This disrupts the thioredoxin-mediated monomerization of STAYGREEN, a key regulator of senescence, and thereby suppresses plant defense responses.

Breeding progress in most crops has relied heavily on the exploitation of variation within the species' primary gene pool, a process which is destined to fail once the supply of novel variants has been exhausted. Accessing a crop's secondary gene pool, as represented by its wild relatives, has the potential to greatly expand the supply of usable genetic variation. The crop in which this approach has been most strongly championed is bread wheat ( ), a species which is particularly tolerant of the introduction of chromosomal segments of exotic origin thanks to the genetic buffering afforded by its polyploid status. While the process of introgression can be in itself cumbersome, a larger problem is that linkage drag and/or imperfect complementation frequently impose a yield and/or quality penalty, which explains the reluctance of breeders to introduce such materials into their breeding populations. Thanks to the development of novel strategies to induce introgression and of genomic tools to facilitate the selection of desirable genotypes, introgression breeding is returning as a mainstream activity, at least in wheat. Accessing variation present in progenitor species has even been able to drive genetic advance in grain yield. The current resurgence of interest in introgression breeding can be expected to result in an increased deployment of exotic genes in commercial wheat cultivars.