Positional cloning and characterization reveal the role of TaSRN-3D and TaBSR1 in the regulation of seminal root number in wheat.

Seminal roots play a critical role in water and nutrient absorption, particularly in the early developmental stages of wheat. However, the genes responsible for controlling SRN in wheat remain largely unknown. Genetic mapping and functional analyses identified a candidate gene (TraesCS3D01G137200, TaSRN-3D) encoding a Ser/Thr kinase glycogen synthase kinase 3 (STKc_GSK3) that regulated SRN in wheat. Additionally, experiments involving hormone treatment, nitrate absorption and protein interaction were conducted to explore the regulatory mechanism of TaSRN-3D. Results showed that the TaSRN-3D4332 allele inhibited seminal roots initiation and development, while loss-of-function mutants showed significantly higher seminal root number (SRN). Exogenous application of epi-brassinolide could increase the SRN in a HS2-allelic background. Furthermore, chlorate sensitivity and 15N uptake assays revealed that a higher number of seminal roots promoted nitrate accumulation. TaBSR1 (BIN2-related SRN Regulator 1, orthologous to OsGRF4/GL2 in rice) acts as an interactor of TaSRN-3D and promotes TaBSR1 degradation to reduce SRN. This study provides valuable insights into understanding the genetic basis and regulatory network of SRN in wheat, highlighting their roles as potential targets for root-based improvement in wheat breeding.

Reshaped DNA methylation cooperating with homoeolog-divergent expression promotes improved root traits in synthesized tetraploid wheat.

Polyploidization is a major event driving plant evolution and domestication. However, how reshaped epigenetic modifications coordinate gene transcription to generate phenotypic variations during wheat polyploidization is currently elusive. Here, we profiled transcriptomes and DNA methylomes of two diploid wheat accessions (SlSl and AA) and their synthetic allotetraploid wheat line (SlSlAA), which displayed elongated root hair and improved root capability for nitrate uptake and assimilation after tetraploidization. Globally decreased DNA methylation levels with a reduced difference between subgenomes were observed in the roots of SlSlAA. DNA methylation changes in first exon showed strong connections with altered transcription during tetraploidization. Homoeolog-specific transcription was associated with biased DNA methylation as shaped by homoeologous sequence variation. The hypomethylated promoters showed significantly enriched binding sites for MYB, which may affect gene transcription in response to root hair growth. Two master regulators in root hair elongation pathway, AlCPC and TuRSL4, exhibited upregulated transcription levels accompanied by hypomethylation in promoter, which may contribute to the elongated root hair. The upregulated nitrate transporter genes, including NPFs and NRTs, also are significantly associated with hypomethylation, indicating an epigenetic-incorporated regulation manner in improving nitrogen use efficiency. Collectively, these results provided new insights into epigenetic changes in response to crop polyploidization and underscored the importance of epigenetic regulation in improving crop traits.

TaNAM-6A is essential for nitrogen remobilisation and regulates grain protein content in wheat (Triticum aestivum L.).

Grain protein content (GPC) is a crucial quality trait in bread wheat, which is influenced by the key transcription factor TaNAM. However, the regulatory mechanisms of TaNAM have remained largely elusive. In this study, a new role of TaNAM was unveiled in regulating nitrogen remobilisation which impacts GPC. The TaNAM knockout mutants generated by clustered regularly interspaced short palindromic repeats/Cas9 exhibited significantly delayed senescence and lower GPC, while overexpression of TaNAM-6A resulted in premature senility and much higher GPC. Further analysis revealed that TaNAM directly activates the genes TaNRT1.1 and TaNPF5.5s, which are involved in nitrogen remobilisation. This activity aids in the transfer of nitrogen from leaves to grains for protein synthesis. In addition, an elite allele of TaNAM-6A, associated with high GPC, was identified as a candidate gene for breeding high-quality wheat. Overall, our work not only elucidates the potential mechanism of TaNAM-6A affecting bread wheat GPC, but also highlights the significance of nitrogen remobilisation from senescent leaves to grains for protein accumulation. Moreover, our research provides a new target and approach for improving the quality traits of wheat, particularly the GPC.

The efficacy and safety of iGlarLixi versus IDegAsp in Chinese people with type 2 diabetes suboptimally controlled with oral antidiabetic drugs: The Soli-D randomized controlled trial.

AIM: To compare the efficacy and safety of a fixed-ratio combination of insulin glargine 100 U/mL plus lixisenatide (iGlarLixi) with premixed insulin, insulin degludec plus insulin aspart (IDegAsp), in Chinese people with type 2 diabetes (T2D) suboptimally controlled with oral antidiabetic drug(s) (OADs). METHODS: In Soli-D, a 24-week, multicentre, open-label, study, insulin-naïve adults were randomized 1:1 to once-daily injections of iGlarLixi (n = 291) or IDegAsp (n = 291), with continued metformin ± sodium-glucose co-transporter-2 inhibitors. The primary endpoint was non-inferiority in HbA1c change from baseline to week 24. Key secondary endpoints included superiority in HbA1c change and body weight (BW) change at week 24. Hypoglycaemia rates were also assessed. RESULTS: At week 24, iGlarLixi showed non-inferiority and superiority over IDegAsp in HbA1c reduction (least squares [LS] mean difference: -0.20 [95% confidence interval {CI}: -0.33, -0.07]; P < .001 for non-inferiority; [97.5% CI: -0.35, -0.05]; P = .003 for superiority). iGlarLixi decreased BW and IDegAsp increased BW from baseline to week 24, with a statistically significant LS mean difference of -1.49 kg in favour of iGlarLixi (97.5% CI: -2.32, -0.66; P < .001). Event rates (per person-year) for American Diabetes Association (ADA) Level 1, 2 or 3 hypoglycaemia were lower for iGlarLixi (1.90) versus IDegAsp (2.72) (relative risk: 0.71; 95% CI: 0.52, 0.98). No ADA Level 3 hypoglycaemia or unexpected safety findings were reported. CONCLUSIONS: In Chinese people with T2D suboptimally controlled with OADs, once-daily iGlarLixi provided better glycaemic control with BW benefit and lower hypoglycaemia event rates versus IDegAsp.

Structural basis for the dynamic chaperoning of disordered clients by Hsp90.

Molecular chaperone heat shock protein 90 (Hsp90) is a ubiquitous regulator that fine-tunes and remodels diverse client proteins, exerting profound effects on normal biology and diseases. Unraveling the mechanistic details of Hsp90's function requires atomic-level insights into its client interactions throughout the adenosine triphosphate-coupled functional cycle. However, the structural details of the initial encounter complex in the chaperone cycle, wherein Hsp90 adopts an open conformation while engaging with the client, remain elusive. Here, using nuclear magnetic resonance spectroscopy, we determined the solution structure of Hsp90 in its open state, bound to a disordered client. Our findings reveal that Hsp90 uses two distinct binding sites, collaborating synergistically to capture discrete hydrophobic segments within client proteins. This bipartite interaction generates a versatile complex that facilitates rapid conformational sampling. Moreover, our investigations spanning various clients and Hsp90 orthologs demonstrate a pervasive mechanism used by Hsp90 orthologs to accommodate the vast array of client proteins. Collectively, our work contributes to establish a unified conceptual and mechanistic framework, elucidating the intricate interplay between Hsp90 and its clients.