NF-YA transcription factors suppress jasmonic acid-mediated antiviral defense and facilitate viral infection in rice

Two different viral proteins suppress NUCLEAR FACTOR-YC-mediated antiviral immunity during infection in rice

Plant viruses have multiple strategies to counter and evade the host's antiviral immune response. However, limited research has been conducted on the antiviral defense mechanisms commonly targeted by distinct types of plant viruses. In this study, we discovered that NUCLEAR FACTOR-YC (NF-YC) and NUCLEAR FACTOR-YA (NF-YA), 2 essential components of the NF-Y complex, were commonly targeted by viral proteins encoded by 2 different rice (Oryza sativa L.) viruses, rice stripe virus (RSV, Tenuivirus) and southern rice black streaked dwarf virus (SRBSDV, Fijivirus). In vitro and in vivo experiments showed that OsNF-YCs associate with OsNF-YAs and inhibit their transcriptional activation activity, resulting in the suppression of OsNF-YA-mediated plant susceptibility to rice viruses. Different viral proteins RSV P2 and SRBSDV SP8 directly disrupted the association of OsNF-YCs with OsNF-YAs, thereby suppressing the antiviral defense mediated by OsNF-YCs. These findings suggest an approach for conferring broad-spectrum disease resistance in rice and reveal a common mechanism employed by viral proteins to evade the host's antiviral defense by hindering the antiviral capabilities of OsNF-YCs.

NF-YC15 transcription factor activates ethylene biosynthesis and improves cassava disease resistance

The nuclear factor Y (NF-Y) transcription factors play important roles in plant development and physiological responses. However, the relationship between NF-Y, plant hormone and plant stress resistance in tropical crops remains unclear. In this study, we identified MeNF-YC15 gene in the NF-Y family that significantly responded to Xanthomonas axonopodis pv. manihotis (Xam) treatment. Using MeNF-YC15-silenced and -overexpressed cassava plants, we elucidated that MeNF-YC15 positively regulated disease resistance to cassava bacterial blight (CBB). Notably, we illustrated MeNF-YC15 downstream genes and revealed the direct genetic relationship between MeNF-YC15 and 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase (MeACO1)-ethylene module in disease resistance, as evidenced by the rescued disease susceptibility of MeNF-YC15 silenced cassava plants with ethylene treatment or overexpressing MeACO1. In addition, the physical interaction between 2C-type protein phosphatase 1 (MePP2C1) and MeNF-YC15 inhibited the transcriptional activation of MeACO1 by MeNF-YC15. In summary, MePP2C1-MeNF-YC15 interaction modulates ethylene biosynthesis and cassava disease resistance, providing gene network for cassava genetic improvement.

Histone deacetylase OsHDA706 orchestrates rice broad-spectrum antiviral immunity and is impeded by a viral effector

Lysine acetylation is a dynamic post-translational modification of proteins. Extensive studies have revealed that the acetylation modulated by histone acetyltransferases and histone deacetylases (HDACs) plays a crucial role in regulating protein function. However, there has been limited focus on how HDACs regulate jasmonic acid (JA) biosynthesis in plants. Here, we uncover that the protein stability of OsLOX14, a critical enzyme involved in JA biosynthesis, is regulated by a histone deacetylase, OsHDA706, and is hindered by a viral protein. Our results show that OsHDA706 deacetylates OsLOX14 and enhances the stability of OsLOX14, leading to JA accumulation and an improved broad-spectrum rice antiviral defense. Furthermore, we found that the viral protein P2, encoded by the destructive rice stripe virus, disrupts the association of OsHDA706-OsLOX14, promoting viral infection. Overall, our findings reveal how HDAC manipulates the interplay of deacetylation and protein stability of a JA biosynthetic enzyme to enhance plant antiviral responses.

Exploring the shared pathogenic strategies of independently evolved effectors across distinct plant viruses

Plants have developed very diverse strategies to defend themselves against viral pathogens, among which plant hormones play pivotal roles. In response, some viruses have also deployed multifunctional viral effectors that effectively hijack key component hubs to counter or evade plant immune surveillance. Although significant progress has been made toward understanding counter-defense strategies that manipulate plant hormone regulatory molecules, these efforts have often been limited to an individual virus or specific host target/pathway. This review provides new insights into broad-spectrum antiviral responses in rice triggered by key components of phytohormone signaling, and highlights the common features of counter-defense strategies employed by distinct rice-infecting RNA viruses. These strategies involve the secretion of multifunctional virulence effectors that target the sophisticated phytohormone system, dampening immune responses by engaging with the same host targets. Additionally, the review provides an in-depth exploration of various viral effectors, emphasizing tertiary structure-based research and shared host targets. Understanding these conserved characteristics in detail may pave the way for molecular drug design, opening new opportunities to enhance broad-spectrum antiviral trials through precise engineering.

Plant virology in the 21st century in China: Recent advances and future directions

Plant viruses are a group of intracellular pathogens that persistently threaten global food security. Significant advances in plant virology have been achieved by Chinese scientists over the last 20 years, including basic research and technologies for preventing and controlling plant viral diseases. Here, we review these milestones and advances, including the identification of new crop-infecting viruses, dissection of pathogenic mechanisms of multiple viruses, examination of multilayered interactions among viruses, their host plants, and virus-transmitting arthropod vectors, and in-depth interrogation of plant-encoded resistance and susceptibility determinants. Notably, various plant virus-based vectors have also been successfully developed for gene function studies and target gene expression in plants. We also recommend future plant virology studies in China.

Biochemical and Transcriptome Analyses Reveal a Stronger Capacity for Photosynthate Accumulation in Low-Tillering Rice Varieties

Moderate control of rice tillering and the development of rice varieties with large panicles are important topics for future high-yield rice breeding. Herein, we found that low-tillering rice varieties stopped tillering earlier and had a larger leaf area of the sixth leaf. Notably, at 28 days after sowing, the rice seedlings of the low-tillering group had an average single-culm above-ground biomass of 0.84 g, significantly higher than that of the multi-tillering group by 56.26%, and their NSC (non-structural carbohydrate) and starch contents in sheaths were increased by 43.34% and 97.75%, respectively. These results indicated that the low-tillering group of rice varieties had a stronger ability to store photosynthetic products in the form of starch in their sheaths, which was thus more beneficial for their large panicle development. The results of carbon and nitrogen metabolism analyses showed that the low-tillering group had a relatively strong carbon metabolism activity, which was more favorable for the accumulation of photosynthesis products and the following development of large panicles, while the multi-tillering group showed relatively strong nitrogen metabolism activity, which was more beneficial for the development and formation of new organs, such as tillers. Accordingly, in the low-tillering rice varieties, the up-regulated genes were enriched in the pathways mainly related to the synthesis of carbohydrates, while the down-regulated genes were mainly enriched in the nitrogen metabolism pathways. This study provides new insights into the mechanism of rice tillering regulation and promotes the development of new varieties with ideal plant types.

A systematic review of southern rice black-streaked dwarf virus in the age of omics

Southern rice black-streaked dwarf virus (SRBSDV) is one of the most damaging rice viruses. The virus decreases rice quality and yield, and poses a serious threat to food security. From this perspective, this review performed a survey of published studies in recent years to understand the current status of SRBSDV and white-backed planthopper (WBPH, Sogatella furcifera) transmission processes in rice. Recent studies have shown that the interactions between viral virulence proteins and rice susceptibility factors shape the transmission of SRBSDV. Moreover, the transmission of SRBSDV is influenced by the interactions between viral virulence proteins and S. furcifera susceptibility factors. This review focused on the molecular mechanisms of key genes or proteins associated with SRBSDV infection in rice via the S. furcifera vector, and the host defense response mechanisms against viral infection. A sustainable control strategy using RNAi was summarized to address this pest. Finally, we also present a model for screening anti-SRBSDV inhibitors using viral proteins as targets. © 2023 Society of Chemical Industry.

Alternative splicing impacts the rice stripe virus response transcriptome

Alternative splicing (AS) is an important form of post transcriptional modification present in both animals and plants. However, little information was obtained about AS events in response to plant virus infection. In this study, we conducted a genome-wide transcriptome analysis on AS change in rice infected by a devastating virus, Rice stripe virus (RSV). KEGG analysis was performed on the differentially expressed (DE) genes and differentially alternative spliced (DAS) genes. The results showed that DE genes were significantly enriched in the pathway of interaction with plant pathogens. The DAS genes were mainly enriched in basal metabolism and RNA splicing pathways. The heat map clustering showed that DEGs clusters were mainly enriched in regulation of transcription and defense response while differential transcript usage (DTU) clusters were strongly enriched in mRNA splicing and calcium binding. Overall, our results provide a fundamental basis for gene-wide AS changes in rice after RSV infection.

Different viral effectors suppress hormone-mediated antiviral immunity of rice coordinated by OsNPR1

Salicylic acid (SA) and jasmonic acid (JA) are plant hormones that typically act antagonistically in dicotyledonous plants and SA and JA signaling is often manipulated by pathogens. However, in monocotyledonous plants, the detailed SA-JA interplay in response to pathogen invasion remains elusive. Here, we show that different types of viral pathogen can disrupt synergistic antiviral immunity mediated by SA and JA via OsNPR1 in the monocot rice. The P2 protein of rice stripe virus, a negative-stranded RNA virus in the genus Tenuivirus, promotes OsNPR1 degradation by enhancing the association of OsNPR1 and OsCUL3a. OsNPR1 activates JA signaling by disrupting the OsJAZ-OsMYC complex and boosting the transcriptional activation activity of OsMYC2 to cooperatively modulate rice antiviral immunity. Unrelated viral proteins from different rice viruses also interfere with the OsNPR1-mediated SA-JA interplay to facilitate viral pathogenicity, suggesting that this may be a more general strategy in monocot plants. Overall, our findings highlight that distinct viral proteins convergently obstruct JA-SA crosstalk to facilitate viral infection in monocot rice.

Genome-Wide Identification and Functional Analysis of NAP1 in Triticum aestivum

As a main molecular chaperone of histone H2A-H2B, nucleosome assembly protein 1 (NAP1) has been widely researched in many species. However, there is little research investigating the function of NAP1 in Triticum aestivum. To understand the capabilities of the family of NAP1 genes in wheat and the relationship between TaNAP1 genes and plant viruses, we performed comprehensive genome-wide analysis and quantitative real-time polymerase chain reaction (qRT-PCR) for testing expression profiling under hormonal and viral stresses. Our results showed that TaNAP1 was expressed at different levels in different tissues, with higher expression in tissues with high meristematic capacity, such as roots. Furthermore, the TaNAP1 family may participate in plant defense mechanisms. This study provides a systematic analysis of the NAP1 gene family in wheat and lays the foundation for further studies on the function of TaNAP1 in the response of wheat plants to viral infection.

A Rice Receptor-like Protein Negatively Regulates Rice Resistance to Southern Rice Black-Streaked Dwarf Virus Infection

Plants rely on various receptor-like proteins and receptor-like kinases to recognize and defend against invading pathogens. However, research on the role of receptor-like proteins in plant antiviral defense, particularly in rice-virus interactions, is limited. In this study, we identified a receptor-like gene, OsBAP1, which was significantly induced upon infection with southern rice black-streaked dwarf virus (SRBSDV) infection. A viral inoculation assay showed that the OsBAP1 knockout mutant exhibited enhanced resistance to SRBSDV infection, indicating that OsBAP1 plays a negatively regulated role in rice resistance to viral infection. Transcriptome analysis revealed that the genes involved in plant-pathogen interactions, plant hormone signal transduction, oxidation-reduction reactions, and protein phosphorylation pathways were significantly enriched in OsBAP1 mutant plants (osbap1-cas). Quantitative real-time PCR (RT-qPCR) analysis further demonstrated that some defense-related genes were significantly induced during SRBSDV infection in osbap1-cas mutants. Our findings provide new insights into the role of receptor-like proteins in plant immune signaling pathways, and demonstrate that OsBAP1 negatively regulates rice resistance to SRBSDV infection.

Identifying transcription factors associated with Fusarium graminearum virus 2 accumulation in Fusarium graminearum by phenome-based investigation

Fusarium graminearum virus 2 (FgV2) infection induces phenotypic changes like reduction of growth rate and virulence with an alteration of the transcriptome, including various transcription factor (TFs) gene transcripts in Fusarium graminearum. Transcription factors are the primary regulator in many cellular processes and are significant in virus-host interactions. However, a detailed study about specific TFs to understand interactions between FgV2 and F. graminearum has yet to be conducted. We transferred FgV2 to a F. graminearum TF gene deletion mutant library to identify host TFs related to FgV2 infection. FgV2-infected TF mutants were classified into three groups depending on colony growth. The FgV2 accumulation level was generally higher in TF mutants showing more reduced growth. Among these FgV2-infected TF mutants, we found several possible TFs that might be involved in FgV2 accumulation, generation of defective interfering RNAs, and transcriptional regulation of FgDICER-2 and FgAGO-1 in response to virus infection. We also investigated the relation between FgV2 accumulation and production of reactive oxygen species (ROS) and DNA damage in fungal host cells by using DNA damage- or ROS-responsive TF deletion mutants. Our studies provide insights into the host factors related to FgV2 infection and bases for further investigation to understand interactions between FgV2 and F. graminearum.

The NF-Y Transcription Factor Family in Watermelon: Re-Characterization, Assembly of ClNF-Y Complexes, Hormone- and Pathogen-Inducible Expression and Putative Functions in Disease Resistance

Nuclear factor Y (NF-Y) is a heterotrimeric transcription factor that binds to the CCAAT cis-element in the promoters of target genes and plays critical roles in plant growth, development, and stress responses. In the present study, we aimed to re-characterize the ClNF-Y family in watermelon, examine the assembly of ClNF-Y complexes, and explore their possible involvement in disease resistance. A total of 25 ClNF-Y genes (7 ClNF-YAs, 10 ClNF-YBs, and 8 ClNF-YCs) were identified in the watermelon genome. The ClNF-Y family was comprehensively characterized in terms of gene and protein structures, phylogenetic relationships, and evolution events. Different types of cis-elements responsible for plant growth and development, phytohormones, and/or stress responses were identified in the promoters of the ClNF-Y genes. ClNF-YAs and ClNF-YCs were mainly localized in the nucleus, while most of the ClNF-YBs were localized in the cytoplasm of cells. ClNF-YB5, -YB6, -YB7, -YB8, -YB9, and -YB10 interacted with ClNF-YC2, -YC3, -YC4, -YC5, -YC6, -YC7, and -YC8, while ClNF-YB1 and -YB3 interacted with ClNF-YC1. A total of 37 putative ClNF-Y complexes were identified, e.g., ClNF-YA1, -YA2, -YA3, and -YA7 assembled into 13, 8, 8, and 8 ClNF-Y complexes with different ClNF-YB/-YC heterodimers. Most of the ClNF-Y genes responded with distinct expression patterns to defense hormones such as salicylic acid, methyl jasmonate, abscisic acid, and ethylene precursor 1-aminocyclopropane-1-carboxylate, and to infection by the vascular infecting fungus Fusarium oxysporum f. sp. niveum. Overexpression of ClNF-YB1, -YB8, -YB9, ClNF-YC2, and -YC7 in transgenic Arabidopsis resulted in an earlier flowering phenotype. Overexpression of ClNF-YB8 in Arabidopsis led to enhanced resistance while overexpression of ClNF-YA2 and -YC2 resulted in decreased resistance against Botrytis cinerea. Similarly, overexpression of ClNF-YA3, -YB1, and -YC4 strengthened resistance while overexpression of ClNF-YA2 and -YB8 attenuated resistance against Pseudomonas syringae pv. tomato DC3000. The re-characterization of the ClNF-Y family provides a basis from which to investigate the biological functions of ClNF-Y genes in respect of growth, development, and stress response in watermelon, and the identification of the functions of some ClNF-Y genes in disease resistance enables further exploration of the molecular mechanism of ClNF-Ys in the regulation of watermelon immunity against diverse pathogens.

Fine-mapping and candidate gene analysis of qFL-c10-1 controlling fiber length in upland cotton (Gossypium hirsutum L.)

A fiber length QTL, qFL-c10-1, was fine-mapped to a 96.5-kb region containing one gene that has not been characterized in plants. Fiber length is an important component of cotton fiber quality, which is associated with other quality properties such as fiber strength, fiber maturity, and fineness. In our previous studies, a stable QTL qFL-c10-1 controlling fiber length had been identified on chromosome A10 in an upland cotton recombinant inbred line (RIL) population from a cross between Jimian5 and DH962. To fine-map qFL-c10-1, an F₂ population with 1081 individual plants from a cross between a recombinant line DJ61 and Jimian5 was established. Using linkage analysis and progeny recombination experiment, qFL-c10-1 was mapped into a 96.5-kb genomic region that just contained one proper transcript Ghir_A10G022020 (described as GhFL10), an undescribed gene in plants. One 214-bp deletion was identified in the promoter region of DJ61 compared with Jimian5. Quantitative real-time PCR (qRT-PCR) and comparative analysis of parental sequences suggested that GhFL10 was the most promising candidate gene for qFL-c10-1. According to RNA-seq, yeast two-hybrid assay and bimolecular fluorescence complementation (BiFC), we speculate that GhFL10 interacts with NF-YA transcription factors to negatively regulate fiber elongation.

Genome-Wide Identification and Characterization of the NF-YA Gene Family and Its Expression in Response to Different Nitrogen Forms in Populus × canescens

The NF-YA gene family is a class of conserved transcription factors that play important roles in plant growth and development and the response to abiotic stress. Poplar is a model organism for studying the rapid growth of woody plants that need to consume many nutrients. However, studies on the response of the NF-YA gene family to nitrogen in woody plants are limited. In this study, we conducted a systematic and comprehensive bioinformatic analysis of the NF-YA gene family based on Populus × canescens genomic data. A total of 13 PcNF-YA genes were identified and mapped to 6 chromosomes. According to the amino acid sequence characteristics and genetic structure of the NF-YA domains, the PcNF-YAs were divided into five clades. Gene duplication analysis revealed five pairs of replicated fragments and one pair of tandem duplicates in 13 PcNF-YA genes. The PcNF-YA gene promoter region is rich in different cis-acting regulatory elements, among which MYB and MYC elements are the most abundant. Among the 13 PcNF-YA genes, 9 contained binding sites for P. × canescens miR169s. In addition, RT-qPCR data from the roots, wood, leaves and bark of P. × canescens showed different spatial expression profiles of PcNF-YA genes. Transcriptome data and RT-qPCR analysis showed that the expression of PcNF-YA genes was altered by treatment with different nitrogen forms. Furthermore, the functions of PcNF-YA genes in transgenic poplar were analyzed, and the potential roles of PcNF-YA genes in the response of poplar roots to different nitrogen forms were revealed, indicating that these genes regulate root growth and development.