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Crop genetic diversity is essential for adaptation and productivity in agriculture. A previous study revealed that poor allele diversity in wheat commercial cultivars is a major barrier to its further improvement. Homologs within a variety, including paralogs and orthologs in polyploid, account for a large part of the total genes of a species. Homolog diversity, intra-varietal diversity (IVD), and their functions have not been elucidated. Common wheat, an important food crop, is a hexaploid species with three subgenomes. This study analyzed the sequence, expression, and functional diversity of homologous genes in common wheat based on high-quality reference genomes of two representative varieties, a modern commercial variety Aikang 58 (AK58) and a landrace Chinese Spring (CS). A total of 85,908 homologous genes, accounting for 71.9% of all wheat genes, including inparalogs (IPs), outparalogs (OPs), and single-copy orthologs (SORs), were identified, suggesting that homologs are an important part of the wheat genome. The levels of sequence, expression, and functional variation in OPs and SORs were higher than that of IPs, which indicates that polyploids have more homologous diversity than diploids. Expansion genes, a specific type of OPs, made a great contribution to crop evolution and adaptation and endowed crop with special characteristics. Almost all agronomically important genes were from OPs and SORs, demonstrating their essential functions for polyploid evolution, domestication, and improvement. Our results suggest that IVD analysis is a novel approach for evaluating intra-genomic variations, and exploitation of IVD might be a new road for plant breeding, especially for polyploid crops, such as wheat. [ABSTRACT FROM AUTHOR]

Summary: Wheat fixes CO2 by photosynthesis into kernels to nourish humankind. Improving the photosynthesis rate is a major driving force in assimilating atmospheric CO2 and guaranteeing food supply for human beings. Strategies for achieving the above goal need to be improved. Here, we report the cloning and mechanism of CO2ASSIMILATION RATE AND KERNEL‐ENHANCED 1 (CAKE1) from durum wheat (Triticum turgidum L. var. durum). The cake1 mutant displayed a lower photosynthesis rate with smaller grains. Genetic studies identified CAKE1 as HSP90.2‐B, encoding cytosolic molecular chaperone folding nascent preproteins. The disturbance of HSP90.2 decreased leaf photosynthesis rate, kernel weight (KW) and yield. Nevertheless, HSP90.2 over‐expression increased KW. HSP90.2 recruited and was essential for the chloroplast localization of nuclear‐encoded photosynthesis units, for example PsbO. Actin microfilaments docked on the chloroplast surface interacted with HSP90.2 as a subcellular track towards chloroplasts. A natural variation in the hexaploid wheat HSP90.2‐B promoter increased its transcription activity, enhanced photosynthesis rate and improved KW and yield. Our study illustrated an HSP90.2–Actin complex sorting client preproteins towards chloroplasts to promote CO2 assimilation and crop production. The beneficial haplotype of Hsp90.2 is rare in modern varieties and could be an excellent molecular switch promoting photosynthesis rate to increase yield in future elite wheat varieties. [ABSTRACT FROM AUTHOR]

Wheat (Triticum aestivum L.) is a critical food crop feeding the world, but pathogens threaten its production. Wheat Heat Shock Protein 90.2 (HSP90.2) is a pathogen‐inducible molecular chaperone folding nascent preproteins. Here, we used wheat HSP90.2 to isolate clients regulated at the posttranslational level. Tetraploid wheat hsp90.2 knockout mutant was susceptible to powdery mildew, while the HSP90.2 overexpression line was resistant, suggesting that HSP90.2 was essential for wheat resistance against powdery mildew. We next isolated 1500 clients of HSP90.2, which contained a wide variety of clients with different biological classifications. We utilized 2Q2, a nucleotide‐binding leucine repeat‐rich protein, as a model to investigate the potential of HSP90.2 interactome in fungal resistance. The transgenic line co‐suppressing 2Q2 was more susceptible to powdery mildew, suggesting 2Q2 as a novel Pm‐resistant gene. The 2Q2 protein resided in chloroplasts, and HSP90.2 played a critical role in the accumulation of 2Q2 in thylakoids. Our data provided over 1500 HSP90.2 clients with a potential regulation at the protein folding process and contributed a nontypical approach to isolate pathogenesis‐related proteins. Summary Statement: This work revealed over 1500 clients of wheat Heat Shock Protein 90.2, a highly conserved pathogen molecular chaperone folding a wide range of signal transducers. 2Q2, a chloroplast‐localized nucleotide‐binding leucine repeat‐rich (NB‐LRR) protein, was discovered as a novel powdery mildew‐resistant protein, showing the potential of HSP90.2 chaperome in future plant fungal resistance study. [ABSTRACT FROM AUTHOR]

Summary: The synthesis of seed storage protein (SSP) is mainly regulated at the transcriptional level. However, few transcriptional regulators of SSP synthesis have been characterized in common wheat (Triticum aestivum) owing to the complex genome. As the A genome donor of common wheat, Triticum urartu could be an elite model in wheat research considering its simple genome. Here, a novel NAC family transcription factor TuSPR from T. urartu was found preferentially expressed in developing endosperm during grain‐filling stages. In common wheat transgenically overexpressing TuSPR, the content of total SSPs was reduced by c. 15.97% attributed to the transcription declines of SSP genes. Both in vitro and in vivo assays showed that TuSPR bound to the cis‐element 5′‐CANNTG‐3′ distributed in SSP gene promoters and suppressed the transcription. The homolog in common wheat TaSPR shared a conserved function with TuSPR on SSP synthesis suppression. The knock‐down of TaSPR in common wheat resulted in 7.07%–20.34% increases in the total SSPs. Both TuSPR and TaSPR could be superior targets in genetic engineering to manipulate SSP content in wheat, and this work undoubtedly expands our knowledge of SSP gene regulation. [ABSTRACT FROM AUTHOR]

Summary: Starch in wheat grain provides humans with carbohydrates and influences the quality of wheaten food. However, no transcriptional regulator of starch synthesis has been identified first in common wheat (Triticum aestivum) due to the complex genome.Here, a novel basic leucine zipper (bZIP) family transcription factor TubZIP28 was found to be preferentially expressed in the endosperm throughout grain‐filling stages in Triticum urartu, the A genome donor of common wheat.When TubZIP28 was overexpressed in common wheat, the total starch content increased by c. 4%, which contributed to c. 5% increase in the thousand kernel weight. The grain weight per plant of overexpression wheat was also elevated by c. 9%. Both in vitro and in vivo assays showed that TubZIP28 bound to the promoter of cytosolic AGPase and enhanced both the transcription and activity of the latter. Knockout of the homologue TabZIP28 in common wheat resulted in declines of both the transcription and activity of cytosolic AGPase in developing endosperms and c. 4% reduction of the total starch in mature grains.To the best of our knowledge, TubZIP28 and TabZIP28 are transcriptional activators of starch synthesis first identified in wheat, and they could be superior targets to improve the starch content and yield potential of wheat. [ABSTRACT FROM AUTHOR]

Transposable elements (TEs) play a pivotal role in reshaping the plant genome. Helitrons represent a new class of transposable elements recently discovered in animals and plants. Helitrons , DNA transposons that replicate via a rolling-circle replication mechanism, are a major driving force behind genome evolution. Since the recent divergence of the modern cultivars (e.g., AK58) and landraces (e.g., Chinese Spring), Helitrons appear to have contributed greatly to genome variability. We first identified 214,665 Helitrons in AK58 by HelitronScanner software and further detected 18,668 tandem duplicated Helitron regions (TDHRs) from all the Helitrons identified. There are 39% of TDHRs (7289) translocated since the divergence of the AK58 and Chinese Spring genomes. What interested us even more are the 462 TDHRs exclusive to the AK58 genome. We also found 235 TDHRs in the 21 centromeric regions and these TDHRs contributed to centromere plasticity. Another very interesting DNA transposon, CACTA, accounting for 15% of AK58 genome, was also the focus of this study because they often inserted into gene rich regions. We found that CACTAs have inserted into many agronomically important genes, such as seed dormancy gene TaMFT and vernalization gene TaVrn1 , indicating the important role of CACTAs in modern wheat adaptation. • Our search led to the identification of 18,668 tandem duplicated regions potentially mediated by Helitrons, (TDHRs), of which significant translocations (39%) occurred after the divergence between AK58 and Chinese Spring. • Of importance, we discovered 462 THDRs exclusive to AK58 and 235 TDHRs localized to centromeric regions potentially contributing to genome plasticity. • From these observations we conclude the Helitrons contributed immensely towards the domestication of wheat. • We also perform analysis of the CACTA family of transposable elements which constitutes ~15% of the genome and their insertion into genes bestowing agronomic important traits as an evidence into their important role in adaptation. [ABSTRACT FROM AUTHOR]

Abstract: The functional analysis of the sodium exchanger SOS1 from wheat, TaSOS1, was undertaken using Saccharomyces cerevisiae as a heterologous expression system. The TaSOS1 protein, with significant sequence homology to SOS1 sodium exchangers from Arabidopsis and rice, is abundant in roots and leaves, and is induced by salt treatment. TaSOS1 suppressed the salt sensitivity of a yeast strain lacking the major Na+ efflux systems by decreasing the cellular Na+ content while increasing K+ content. Na+/H+ exchange activity of purified plasma membrane from yeast cells expressing TaSOS1 was higher than controls transformed with empty vector. These results demonstrate that TaSOS1 contributes to plasma membrane Na+/H+ exchange. [Copyright &y& Elsevier]

Abstract: Kernel hardness is mainly controlled by one major genetic locus on the short arm of chromosome 5D in bread wheat. Twelve Chinese and CIMMYT wheat cultivars were characterized for the deletion region of Pina-D1b genotype and developing a novel STS marker for this allele. PCR and SDS-PAGE were used to confirm the Pina-D1b genotype, and then 20 pairs of primers were designed to amplify the fragment including deletion region in Pina-D1b genotype by primer walking strategy. An STS marker Pina-N spanning deletion region in Pina-D1b was developed and sequencing results showed that all of 10 Pina-D1b genotypes uniformly possessed a 15,380 bp deletion in comparison with that of Chinese Spring with wild type. This study provided an alternative method to exam Pina-D1b by molecular marker and will accelerate identification of puroindoline alleles in bread wheat. [Copyright &y& Elsevier]