Maternal nitric oxide homeostasis impacts female gametophyte development under optimal and stress conditions.

In adverse environments, the number of fertilizable female gametophytes (FGs) in plants is reduced, leading to increased survival of the remaining offspring. How the maternal plant perceives internal growth cues and external stress conditions to alter FG development remains largely unknown. We report that homeostasis of the stress signaling molecule nitric oxide (NO) plays a key role in controlling FG development under both optimal and stress conditions. NO homeostasis is precisely regulated by S-nitrosoglutathione reductase (GSNOR). Prior to fertilization, GSNOR protein is exclusively accumulated in sporophytic tissues and indirectly controls FG development in Arabidopsis (Arabidopsis thaliana). In GSNOR null mutants, NO species accumulated in the degenerating sporophytic nucellus, and auxin efflux into the developing FG was restricted, which inhibited FG development, resulting in reduced fertility. Importantly, restoring GSNOR expression in maternal, but not gametophytic tissues, or increasing auxin efflux substrate significantly increased the proportion of normal FGs and fertility. Furthermore, GSNOR overexpression or added auxin efflux substrate increased fertility under drought and salt stress. These data indicate that NO homeostasis is critical to normal auxin transport and maternal control of FG development, which in turn determine seed yield. Understanding this aspect of fertility control could contribute to mediating yield loss under adverse conditions.

Integration of genome-wide association study, linkage analysis, and population transcriptome analysis to reveal the TaFMO1-5B modulating seminal root growth in bread wheat.

Bread wheat, one of the keystone crops for global food security, is challenged by climate change and resource shortage. The root system plays a vital role in water and nutrient absorption, making it essential for meeting the growing global demand. Here, using an association-mapping population composed of 406 accessions, we identified QTrl.Rs-5B modulating seminal root development with a genome-wide association study and validated its genetic effects with two F5 segregation populations. Transcriptome-wide association study prioritized TaFMO1-5B, a gene encoding the flavin-containing monooxygenases, as the causal gene for QTrl.Rs-5B, whose expression levels correlate negatively with the phenotyping variations among our population. The lines silenced for TaFMO1-5B consistently showed significantly larger seminal roots in different genetic backgrounds. Additionally, the agriculture traits measured in multiple environments showed that QTrl.Rs-5B also affects yield component traits and plant architecture-related traits, and its favorable haplotype modulates these traits toward that of modern cultivars, suggesting the application potential of QTrl.Rs-5B for wheat breeding. Consistently, the frequency of the favorable haplotype of QTrl.Rs-5B increased with habitat expansion and breeding improvement of bread wheat. In conclusion, our findings identified and demonstrated the effects of QTrl.Rs-5B on seminal root development and illustrated that it is a valuable genetic locus for wheat root improvement.

TaGSK3 regulates wheat development and stress adaptation through BR-dependent and BR-independent pathways.

The GSK3/SHAGGY-like kinase plays critical roles in plant development and response to stress, but its specific function remains largely unknown in wheat (Triticum aestivum L.). In this study, we investigated the function of TaGSK3, a GSK3/SHAGGY-like kinase, in wheat development and response to stress. Our findings demonstrated that TaGSK3 mutants had significant effects on wheat seedling development and brassinosteroid (BR) signalling. Quadruple and quintuple mutants showed amplified BR signalling, promoting seedling development, while a sextuple mutant displayed severe developmental defects but still responded to exogenous BR signals, indicating redundancy and non-BR-related functions of TaGSK3. A gain-of-function mutation in TaGSK3-3D disrupted BR signalling, resulting in compact and dwarf plant architecture. Notably, this mutation conferred significant drought and heat stress resistance of wheat, and enhanced heat tolerance independent of BR signalling, unlike knock-down mutants. Further research revealed that this mutation maintains a higher relative water content by regulating stomatal-mediated water loss and maintains a lower ROS level to reduces cell damage, enabling better growth under stress. Our study provides comprehensive insights into the role of TaGSK3 in wheat development, stress response, and BR signal transduction, offering potential for modifying TaGSK3 to improve agronomic traits and enhance stress resistance in wheat.

The selection and application of peduncle length QTL QPL_6D.1 in modern wheat (Triticum aestivum L.) breeding.

KEY MESSAGE: QPL_6D.1b displayed an additive effect with Rht-B1b and Rht-D1b in reducing wheat plant height and peduncle length, which confers shorter peduncle length and more kernels per spike, and had been broadly selected by Chinese modern wheat cultivars. Peduncle length (PL), as the key component of wheat plant height (PH), plays critical role in determining wheat lodging resistance and wheat pathogen resistance; then, its breeding selection and genetic basis remain largely unclear. Here the PH and PL were investigated in 406 wheat accessions in eight environments. In this study, a PL preferentially QTL QPL_6D.1 was identified in six environments by GWAS, which explained 13.6-24.2% of wheat PL variations in natural population. The allele QPL_6D.1b displayed a significantly additive effect with Rht-B1b and Rht-D1b in controlling PH and PL and could freely combined with Rht-B1b and Rht-D1b in current wheat cultivars. Haplotypic analysis demonstrates the QPL_6D.1b has been selected by Chinese modern wheat cultivar and confers shorter PL and more kernels per spike, highlighting its potentials in wheat breeding.

Pulmonary invasive mucinous adenocarcinoma mimicking pulmonary actinomycosis.

BACKGROUND: Primary pulmonary invasive mucinous adenocarcinoma is a rare and distinct subtype of lung adenocarcinoma. CASE PRESENTATION: A 72-year-old woman presented with productive cough for two months and fever for six days. Chest computed tomography (CT) showed a mass in the left lower lobe. Sputum culture tested negative for bacteria, but the sequence of Actinomyces meyeri was detected by metagenomic next generation sequencing from the bronchoalveolar lavage fluid. It was considered a pathogenic bacterium as the normalized number of DNA sequencing reads was 10 times higher than the normal level. The patient's symptoms alleviated quickly, and the chest CT lesion shrank to a third of the original size following treatment with penicillin for two months. However, a repeat chest CT performed after four months of treatment revealed that the lesion had expanded. Positron emission tomography/CT revealed that fluorodeoxyglucose metabolism was increased in the mass with surrounding ground glass density of the left lower lobe. Furthermore, CT-guided percutaneous lung biopsy was performed, and hematoxylin-eosin staining showed columnar tumor cells with abundant mucin in the cytoplasm with a basal nucleus. Finally, the patient was diagnosed with pulmonary invasive mucinous adenocarcinoma and agreed to undergo a thoracoscopic surgery. CONCLUSIONS: Pulmonary invasive mucinous adenocarcinoma is a subset of lung adenocarcinoma with low incidence rate. The clinical features and CT findings are non-specific. A histopathological diagnosis is of fundamental importance in preventing misdiagnosis.

Factors affecting the rapid changes of protein under short-term heat stress.

BACKGROUND: Protein content determines the state of cells. The variation in protein abundance is crucial when organisms are in the early stages of heat stress, but the reasons affecting their changes are largely unknown. RESULTS: We quantified 47,535 mRNAs and 3742 proteins in the filling grains of wheat in two different thermal environments. The impact of mRNA abundance and sequence features involved in protein translation and degradation on protein expression was evaluated by regression analysis. Transcription, codon usage and amino acid frequency were the main drivers of changes in protein expression under heat stress, and their combined contribution explains 58.2 and 66.4% of the protein variation at 30 and 40 °C (20 °C as control), respectively. Transcription contributes more to alterations in protein content at 40 °C (31%) than at 30 °C (6%). Furthermore, the usage of codon AAG may be closely related to the rapid alteration of proteins under heat stress. The contributions of AAG were 24 and 13% at 30 and 40 °C, respectively. CONCLUSION: In this study, we analyzed the factors affecting the changes in protein expression in the early stage of heat stress and evaluated their influence.

BRS1 mediates plant redox regulation and cold responses.

BACKGROUND: Brassinosteroid-insensitive 1 suppressor 1 (BRS1) is a serine carboxypeptidase that mediates brassinosteroid signaling and participates in multiple developmental processes in Arabidopsis. However, little is known about the precise role of BRS1 in this context. RESULTS: In this study, we analyzed transcriptional and proteomic profiles of Arabidopsis seedlings overexpressing BRS1 and found that this gene was involved in both cold stress responses and redox regulation. Further proteomic evidence showed that BRS1 regulated cell redox by indirectly interacting with cytosolic NADP + -dependent isocitrate dehydrogenase (cICDH). One novel alternative splice form of BRS1 was identified in over-expression mutants brs1-1D, which may confer a new role in plant development and stress responses. CONCLUSIONS: This study highlights the role of BRS1 in plant redox regulation and stress responses, which extends our understanding of extracellular serine carboxypeptidases.

Auxin efflux controls orderly nucellar degeneration and expansion of the female gametophyte in Arabidopsis.

The nucellus tissue in flowering plants provides nutrition for the development of the female gametophyte (FG) and young embryo. The nucellus degenerates as the FG develops, but the mechanism controlling the coupled process of nucellar degeneration and FG expansion remains largely unknown. The degeneration process of the nucellus and spatiotemporal auxin distribution in the developing ovule before fertilization were investigated in Arabidopsis thaliana. Nucellar degeneration before fertilization occurs through vacuolar cell death and in an ordered degeneration fashion. This sequential nucellar degeneration is controlled by the signalling molecule auxin. Auxin efflux plays the core role in precisely controlling the spatiotemporal pattern of auxin distribution in the nucellus surrounding the FG. The auxin efflux carrier PIN1 transports maternal auxin into the nucellus while PIN3/PIN4/PIN7 further delivers auxin to degenerating nucellar cells and concurrently controls FG central vacuole expansion. Notably, auxin concentration and auxin efflux are controlled by the maternal tissues, acting as a key communication from maternal to filial tissue.

Hybrid sequencing reveals insight into heat sensing and signaling of bread wheat.

Wheat (Triticum aestivum L.), a globally important crop, is challenged by increasing temperatures (heat stress, HS). However its polyploid nature, the incompleteness of its genome sequences and annotation, the lack of comprehensive HS-responsive transcriptomes and the unexplored heat sensing and signaling of wheat hinder our full understanding of its adaptations to HS. The recently released genome sequences of wheat, as well as emerging single-molecular sequencing technologies, provide an opportunity to thoroughly investigate the molecular mechanisms of the wheat response to HS. We generated a high-resolution spatio-temporal transcriptome map of wheat flag leaves and filling grain under HS at 0 min, 5 min, 10 min, 30 min, 1 h and 4 h by combining full-length single-molecular sequencing and Illumina short reads sequencing. This hybrid sequencing newly discovered 4947 loci and 70 285 transcripts, generating the comprehensive and dynamic list of HS-responsive full-length transcripts and complementing the recently released wheat reference genome. Large-scale analysis revealed a global landscape of heat adaptations, uncovering unexpected rapid heat sensing and signaling, significant changes of more than half of HS-responsive genes within 30 min, heat shock factor-dependent and -independent heat signaling, and metabolic alterations in early HS-responses. Integrated analysis also demonstrated the differential responses and partitioned functions between organs and subgenomes, and suggested a differential pattern of transcriptional and alternative splicing regulation in the HS response. This study provided comprehensive data for dissecting molecular mechanisms of early HS responses in wheat and highlighted the genomic plasticity and evolutionary divergence of polyploidy wheat.

Brassinosteroid Regulates Root Development with Highly Redundant Genes in Hexaploid Wheat.

Brassinosteroid (BR) plays an important role in plant development and biotic and abiotic stress tolerance, but its specific function remains largely unknown in wheat (Triticum aestivum L.), preventing its utilization in this important crop. In this study, the function of BR and its underlying cytological role in wheat root development were comprehensively investigated. Our findings demonstrated that BR has a conserved function in regulating root length in wheat, and novel roles in regulating lateral root emergence and root diameter were uncovered. Analyses of BR homologous gene composition and evolutionary divergence demonstrated that the genetic framework of the wheat BR pathway was close to that of rice, but contained highly redundant homologous copies of genes from the subgenome A, B and D. These homologous copies showed active expression and shared a conserved BR response. The expression of wheat DWF4 and glycogen synthase kinase (GSK) genes in Arabidopsis confirmed that multiple homologous copies maintained their conserved function in regulating root development, highlighting their redundant status and indicating that a special challenge exists in wheat gene modification to deal with this high redundancy. However, our results suggested that the hypermorphic effect of T. aestivum GSK (TaGSK) genes with point mutations may be an effective approach to overcome this redundancy in the manipulation of BR signaling in wheat. Our study provides fundamental data uncovering the function of BR in wheat root development, the underlying genetic basis and a possible strategy to manipulate BR signaling in hexaploid wheat.

Global profiling of alternative splicing landscape responsive to drought, heat and their combination in wheat (Triticum aestivum L.).

Plant can acquire tolerance to environmental stresses via transcriptome reprogramming at transcriptional and alternative splicing (AS) levels. However, how AS coordinates with transcriptional regulation to contribute to abiotic stresses responses is still ambiguous. In this study, we performed genome-wide analyses of AS responses to drought stress (DS), heat stress (HS) and their combination (HD) in wheat seedlings, and further compared them with transcriptional responses. In total, we found 200, 3576 and 4056 genes exhibiting significant AS pattern changes in response to DS, HS and HD, respectively, and combined drought and heat stress can induce specific AS compared with individual one. In addition, wheat homeologous genes exhibited differential AS responses under stress conditions that more AS events occurred on B subgenome than on A and D genomes. Comparison of genes regulated at AS and transcriptional levels showed that only 12% of DS-induced AS genes were subjected to transcriptional regulation, whereas the proportion increased to ~40% under HS and HD. Functional enrichment analysis revealed that abiotic stress-responsive pathways tended to be highly overrepresented among these overlapped genes under HS and HD. Thus, we proposed that transcriptional regulation may play a major role in response to DS, which coordinates with AS regulation to contribute to HS and HD tolerance in wheat.

Metabolic adaptation of wheat grain contributes to a stable filling rate under heat stress.

Wheat (Triticum aestivum) is particularly vulnerable to heat stress during the grain filling stage, and this can adversely affect the final yield. However, the underlying physiological and molecular mechanisms are largely unknown. In this study, the effects of heat stress on grain filling were investigated using wheat varieties with different levels of thermotolerance. Decreased grain weights and filling durations, increased protein contents, and stable filling rates across diverse varieties under different heat regimes suggested a general mechanism for heat adaptation. Proteomic analysis identified 309 heat-responsive proteins (HRPs), and revealed a general decrease in protein synthesis components and metabolic proteins, but a significant increase in stress-response proteins and storage proteins. Metabolomic analysis identified 98 metabolites specifically changed by heat stress, and suggested a global decrease in the content of carbohydrate metabolites, an increased content of amino acids, and stable levels of starch synthesis precursors. The energy-consuming HRPs suggested that less energy was channelled into metabolism and protein synthesis, whereas more energy was allocated to the stress response under elevated heat conditions. Collectively, the data demonstrated a widely distributed mechanism for heat adaptation of metabolism, in which the assimilation and energy required for metabolism and protein synthesis are reallocated to heat protection and deposition of reserves, resulting in increased storage protein accumulation and a stable filling rate.

BRS1 Function in Facilitating Lateral Root Emergence in Arabidopsis.

The BRS1 (BRI1 Suppressor 1) gene encodes a serine carboxypeptidase that plays a critical role in the brassinosteroid signaling pathway. However, its specific biological function remains unclear. In this study, the developmental role of BRS1 was investigated in Arabidopsis thaliana. We found that overexpressing BRS1 resulted in significantly more lateral roots in different Arabidopsis ecotypes (WS2 and Col-0) and in brassinosteroid mutants (bri1-5 and det2-28). Further research showed that BRS1 facilitates the process whereby lateral root primordia break through the endodermis, cortex, and epidermis. Consistent with this, BRS1 was found to be highly expressed in the root endodermis and accumulated in the extracellular space around the dome of the lateral root primordia. Taken together, these results highlight the role of BRS1 in the process of lateral root emergence and provide new insight into the role of serine carboxypeptidases in plant root development.

Vascular endothelial growth factor B coordinates metastasis of non-small cell lung cancer.

Neovascularization is critical for the invasion and metastasis of non-small cell lung cancer (NSCLC). However, the molecular mechanism underlying the control of neovascularization of NSCLC is not completely understood. Both vascular endothelial growth factor B (VEGF-B) and matrix metalloproteinases 9 (MMP9) play essential roles in neovascularization of NSCLC. Here, we examined whether VEGF-B and MMP9 may affect each other to coordinate the neovascularization process in NSCLC. We found strong positive correlation of VEGF-B and MMP9 levels in the NSCLC from the patients. Moreover, patients that had NSCLC with metastasis had significantly higher levels of VEGF-B and MMP9 in the primary cancer. Using a human NSCLC line A549, we found that overexpression of VEGF-B increased expression of MMP9, while inhibition of VEGF-B decreased expression of MMP9. On the other hand, overexpression of MMP9 increased expression of VEGF-B, while inhibition of MMP9 decreased expression of VEGF-B. These data suggest that expression of VEGF-B and MMP9 may activate each other to enhance neovascularization. We then analyzed the underlying mechanism. Application of a specific ERK/MAPK inhibitor but not a PI3K/Akt inhibitor to VEGF-B-overexpressing A549 cells substantially abolished the effect of VEGF-B on MMP9 activation, while application of a specific PI3K/Akt inhibitor but not an ERK/MAPK inhibitor to MMP9-overexpressing A549 cells substantially abolished the effect of MMP9 on VEGF-B activation, suggesting that VEGF-B may activate MMP9 via ERK/MAPK signaling pathway, while MMP9 may activate VEGF-B via PI3K/Akt signaling pathway. Thus, our data highlight a coordinating relationship between VEGF-B and MMP9 in the regulation of neovascularization in NSCLC.

Genetic evidence for an indispensable role of somatic embryogenesis receptor kinases in brassinosteroid signaling.

The Arabidopsis thaliana somatic embryogenesis receptor kinases (SERKs) consist of five members, SERK1 to SERK5, of the leucine-rich repeat receptor-like kinase subfamily II (LRR-RLK II). SERK3 was named BRI1-Associated Receptor Kinase 1 (BAK1) due to its direct interaction with the brassinosteroid (BR) receptor BRI1 in vivo, while SERK4 has also been designated as BAK1-Like 1 (BKK1) for its functionally redundant role with BAK1. Here we provide genetic and biochemical evidence to demonstrate that SERKs are absolutely required for early steps in BR signaling. Overexpression of four of the five SERKs-SERK1, SERK2, SERK3/BAK1, and SERK4/BKK1-suppressed the phenotypes of an intermediate BRI1 mutant, bri1-5. Overexpression of the kinase-dead versions of these four genes in the bri1-5 background, on the other hand, resulted in typical dominant negative phenotypes, resembling those of null BRI1 mutants. We isolated and generated single, double, triple, and quadruple mutants and analyzed their phenotypes in detail. While the quadruple mutant is embryo-lethal, the serk1 bak1 bkk1 triple null mutant exhibits an extreme de-etiolated phenotype similar to a null bri1 mutant. While overexpression of BRI1 can drastically increase hypocotyl growth of wild-type plants, overexpression of BRI1 does not alter hypocotyl growth of the serk1 bak1 bkk1 triple mutant. Biochemical analysis indicated that the phosphorylation level of BRI1 in serk1 bak1 bkk1 is incapable of sensing exogenously applied BR. As a result, the unphosphorylated level of BES1 has lost its sensitivity to the BR treatment in the triple mutant, indicating that the BR signaling pathway has been completely abolished in the triple mutant. These data clearly demonstrate that SERKs are essential to the early events of BR signaling.

Deciphering the Transcriptional Regulatory Network Governing Starch and Storage Protein Biosynthesis in Wheat for Breeding Improvement.

Starch and seed storage protein (SSP) composition profoundly impact wheat grain yield and quality. To unveil regulatory mechanisms governing their biosynthesis, transcriptome, and epigenome profiling is conducted across key endosperm developmental stages, revealing that chromatin accessibility, H3K27ac, and H3K27me3 collectively regulate SSP and starch genes with varying impact. Population transcriptome and phenotype analyses highlight accessible promoter regions' crucial role as a genetic variation resource, influencing grain yield and quality in a core collection of wheat accessions. Integration of time-serial RNA-seq and ATAC-seq enables the construction of a hierarchical transcriptional regulatory network governing starch and SSP biosynthesis, identifying 42 high-confidence novel candidates. These candidates exhibit overlap with genetic regions associated with grain size and quality traits, and their functional significance is validated through expression-phenotype association analysis among wheat accessions and loss-of-function mutants. Functional analysis of wheat abscisic acid insensitive 3-A1 (TaABI3-A1) with genome editing knock-out lines demonstrates its role in promoting SSP accumulation while repressing starch biosynthesis through transcriptional regulation. Excellent TaABI3-A1Hap1 with enhanced grain weight is selected during the breeding process in China, linked to altered expression levels. This study unveils key regulators, advancing understanding of SSP and starch biosynthesis regulation and contributing to breeding enhancement.

BAK1 directly regulates brassinosteroid perception and BRI1 activation.

Plants utilize plasma membrane-localized receptor-like kinases (RLKs) to sense extracellular signals to coordinate growth, development, and innate immune responses. BAK1 regulates multiple signaling pathways acting as a co-receptor of several distinct ligand-binding RLKs. It has been debated whether BAK1 serves as an essential regulatory component or only a signal amplifier without pathway specificity. This issue has been clarified recently. Genetic and structural analyses indicated that BAK1 and its homologs play indispensible roles in mediating brassinosteroid (BR) signaling pathway by directly perceiving the ligand BR and activating the receptor of BR, BRI1. The mechanism revealed by these studies now serves as a paradigm for how a pair of RLKs can function together in ligand binding and subsequent initiation of signaling. [Figure: see text] Jia Li (Corresponding author).

Wheat genomic study for genetic improvement of traits in China.

Bread wheat (Triticum aestivum L.) is a major crop that feeds 40% of the world's population. Over the past several decades, advances in genomics have led to tremendous achievements in understanding the origin and domestication of wheat, and the genetic basis of agronomically important traits, which promote the breeding of elite varieties. In this review, we focus on progress that has been made in genomic research and genetic improvement of traits such as grain yield, end-use traits, flowering regulation, nutrient use efficiency, and biotic and abiotic stress responses, and various breeding strategies that contributed mainly by Chinese scientists. Functional genomic research in wheat is entering a new era with the availability of multiple reference wheat genome assemblies and the development of cutting-edge technologies such as precise genome editing tools, high-throughput phenotyping platforms, sequencing-based cloning strategies, high-efficiency genetic transformation systems, and speed-breeding facilities. These insights will further extend our understanding of the molecular mechanisms and regulatory networks underlying agronomic traits and facilitate the breeding process, ultimately contributing to more sustainable agriculture in China and throughout the world.