Enemies atpeace:Recentprogressin Agrobacterium-mediated cereal transformation

Agrobacterium tumefaciens mediated plant transformation is a versatile tool for plant genetic engineering following its discovery nearly half a century ago.Numerous modifications were made in its application to increase efficiency,especially in the recalcitrant major cereals plants.Recent breakthroughs in transformation efficiency continue its role as a mainstream technique in CRISPR/Cas-based genome editing and gene stacking.These modifications led to higher transformation frequency and lower but more stable transgene copies with the capability to revolutionize modern agriculture.In this review,we provide a brief overview of the history of Agrobacterium-mediated plant transformation and focus on the most recent progress to improve the system in both the Agrobacterium and the host recipient.A promising future for transformation in biotechnology and agriculture is predicted.

Wheat functional genomics in the era of next generation sequencing: An update

Bread wheat is not only an important cereal crop but also a model for study of an allopolyploid plant with a large, highly repetitive genome. Advances in next-generation sequencing(NGS) technology provide needed throughput to conquer the enormous size of the wheat genome. Multiple high quality reference genome sequences will soon be available. Full-scale wheat functional genomics studies are dawning. In this review we highlight the available tools and methodologies for wheat functional genomics research developed with the assistance of NGS technology and recent progress, particularly the concerted effort in generating multiple reference genomes, strategies to attain genome-wide genetic variation, genome-wide association studies, mutant population generation, and NGS-supported gene cloning and functional characterization. These resources and platforms lay a solid foundation for wheat research, leading to a new era of wheat functional genomics that will bridge the gap between genotype and phenotype.Dissection of wheat genomes and gene functions should assist in genomics-assisted selection and facilitate breeding of elite varieties for sustainable agriculture in China and the world.

The soft glumes of common wheat are sterile-lemmas as determined by the domestication gene Q

The Q gene in common wheat encodes an APETALA2(AP2) transcription factor that causes the free threshing attribute. Wheat spikelets bearing several florets are subtended by a pair of soft glumes that allow free liberation of seeds. In wild species, the glumes are tough and rigid,making threshing difficult. However, the nature of these "soft glumes", caused by the domestication allele Q is not clear. Here, we found that over expression of Q in common wheat leads to homeotic florets at glume positions. We provide phenotypic, microscopy, and marker genes evidence to demonstrate that the soft glumes of common wheat are in fact lemma-like organs, or so-called sterile-lemmas. By comparing the structures subtending spikelets in wheat and other crops such as rice and maize, we found that AP2 genes may play conserved functions in grasses by manipulating vestigial structures, such as floret-derived soft glumes in wheat and empty glumes in rice. Conversion of these seemingly vegetative organs to reproductive organs may be useful in yield improvement of crop species.

WheatGene: A genomics database for common wheat and its related species

Common wheat(Triticum aestivum) is a hexaploid plant(AABBDD) derived from genetically related tetraploid wheat T. turgidum(AABB) and a diploid goatgrass Aegilops tauschii(DD). Recent advances in sequencing technology and genome assembly strategies allow the acquisition of multiple wheat genomes, calling for a centralized database to store, manage and query the genomics information in a manner to reflect their evolutionary relationship and to perform effective comparative genome analysis. Here,we built WheatGene, a database that contains five wheat genomes of 318,102 genes and 945,900 transcripts and their expression information in 998 RNA-seq samples that can be searched and compared in an interactive manner. WheatGene was developed with Drupal, a popular content management system and the toolkit Tripal managed the biological information. The database was accessible through a web browser with species, search, gene expression, tools, and literature entries. Tools available were BLAST,synteny viewer, map viewer, JBrowse, data downloads, gene expression heatmap and bar chart, and homologs viewer. Moreover, the map viewer connected genomics data with genetic maps and QTL that can be searched for markers for molecular breeding. WheatGene was developed with open-source modules and libraries. WheatGene is available at http://wheatgene.agrinome.org.

Wheat breeding history reveals synergistic selection of pleiotropic genomic sites for plant architecture and grain yield

Diversity surveys of crop germplasm are important for gaining insights into the genomic basis for plant architecture and grain yield improvement,which is still poorly understood in wheat.In this study,we exome sequenced 287 wheat accessions that were collected in the past 100 years.Population genetics analysis identified that 6.7%of the wheat genome falls within the selective sweeps between landraces and cultivars,which harbors the genes known for yield improvement.These regions were asymmetrically distributed on the A and B subgenomes with regulatory genes being favorably selected.Genome-wide association study(GWAS)identified genomic loci associated with traits for yield potential,and two underlying genes,TaARF12 encoding an auxin response factor and TaDEP1 encoding the G-proteinγ-subunit,were located and characterized to pleiotropically regulate both plant height and grain weight.Elite single-nucleotide haplotypes with increased allele frequency in cultivars relative to the landraces were identified and found to have accumulated over the course of breeding.Interestingly,we found that TaARF12 and TaDEP1 function in epistasis with the classical plant height Rht-1 locus,leading to propose a“Green Revolution”-based working model for historical wheat breeding.Collectively,our study identifies selection signatures that fine-tune the gibberellin pathway during modern wheat breeding and provides a wealth of genomic diversity resources for the wheat research community.

Genome Editing and Double-Fluorescence Proteins Enable Robust Maternal Haploid Induction and Identification in Maize

Dear Editor Genome editing technologies have paved the way for exciting and novel applications in plant biotechnology. Doubled haploid （DH） technology has a significant and valuable advantage over traditional approaches in crop breeding. Unlike traditional breeding processes, which may take over eight generations to stabilize the genetic background of interest.

RNAi technology for plant protection and its applicatior in wheat

The RNAi technology takes advantage of the intrinsic RNA interference(RNAi)mechanism that exists in nearly all eukaryotes in which target mRNAs are degraded or functionally suppressed.Significant progress has been made in recent years where RNAi technology is applied to several crops and economic plants for protection against diseases like fungi,pests,and nematode.RNAi technology is also applied in controlling pathogen damages in wheat,one of the most important crops in the world.In this review,we first give a brief introduction of the RNAi technology and the underneath mechanism.We then review the recent progress of its utilization in crops,particular wheat.Finally,we discuss the existing challenges and prospect future development of this technology in crop protection.

Genome-editing of a circadian clock gene TaPRR95 facilitates wheat peduncle growth and heading date

Plant height and heading date are important agronomic traits in wheat(Triticum aestivum L.)that affect final grain yield.In wheat,knowledge of pseudo-response regulator(PRR)genes on agronomic traits is limited.Here,we identify a wheat TaPRR95 gene by genome-wide association studies to be associated with plant height.Triple allele mutant plants produced by CRISPR/Cas9 show increased plant height,particularly the peduncle,with an earlier heading date.The longer peduncle is mainly caused by the increased cell elon-gation at its upper section,whilst the early heading date is accompanied by elevated expression of flow-ering genes,such as TaFT and TacO1.A peduncle-specific transcriptome analysis reveals up-regulated photosynthesis genes and down-regulated IAAVAux genes for auxin signaling inpr95abad plants that may act as a regulatory mechanism to promote robust plant growth.A haplotype analysis identifies a TaPRR95-B haplotype(Hap2)to be closely associated with reduced plant height and increased thousand-grain weight.Moreover,the Hap2 frequency is higher in cultivars than that in landraces,suggesting the artifi-cial selection on the allele during wheat breeding.These findings suggest that TaPRR95 is a regulator for plant height and heading date,thereby providing an important target for wheat yield improvement.