Nuclear factor OsNF-YC5 modulates rice seed germination by regulating synergistic hormone signaling

StNF-YA8-YB20-YC5 module regulates potato tuber dormancy by modulating gibberellin and abscisic acid pathways

The molecular mechanisms involved in the regulation of potato tuber dormancy are complex, involving a variety of related genes and enzymes, which modulate multiple signaling pathways. Nuclear factor-Y (NF-Y) transcription factors (TFs) are widely found in eukaryotes and are involved in the regulation of plant embryonic development, seed germination, fruit ripening, and in response to biotic and abiotic stress. Previously, we found that StNF-YA8 gene expression was increasing with the release of potato tuber dormancy. In this study, it was found that StNF-YA8 overexpressed tubers broke dormancy earlier than non-transgenic (NT) and StNF-YA8 downregulated tubers. Changes in abscisic acid (ABA) and gibberellin (GA) content of different types of tubers at different dormancy periods confirmed that both GA and ABA hormones influenced the differences in dormancy time. This was confirmed by the expression of GA pathway genes StGA3ox1 and StGA20ox1 genes and ABA pathway genes StCYP707A2 and StPP2CA1 genes in different tubers. The four genes described above were further shown to be target genes of the StNF-YA8 TF, which transcriptionally activates the expression of these genes. In addition, we verified the involvement of StNF-YA8 in the tuber dormancy release process by the interacting proteins StNF-YB20 and StNF-YC5, which are able to bind to the StNF-YA8-B20-C5 module to activate the transcription of GA and ABA pathway genes. Our study reveals the StNF-YA8-C5 module activates the transcription of the StCYP707A2, StPP2CA1, StGA3ox1, and StGA20ox1 genes and alters GA and ABA content, accelerating the release of dormancy in potato tubers.

Overexpressing OsNF-YB12 elevated the content of jasmonic acid and impaired drought tolerance in rice

Nuclear factor Y (NF-Y) is an evolutionarily conserved heterotrimeric transcription factor in eukaryotes. In a previous study, OsNF-YB12 was confirmed to be associated with drought tolerance using the Ecotilling method. In this study, real-time quantitative RT-PCR revealed that OsNF-YB12 was induced by various abiotic stresses and phytohormones, with expression levels differing between leaves and roots. Rice overexpressing OsNF-YB12 was more sensitive to salinity and PEG osmotic stresses at seed germination stage, as well as reduced drought tolerance at seedling stage. Notably, the accumulation of free proline and photosynthetic efficiency was significantly declined in OsNF-YB12 transgenic plants following osmotic stimuli. Transcriptomic analysis of transgenic OsNF-YB12 plants indicated that OsNF-YB12 could upregulate terpene metabolism related to defense responses and the expression levels of JAZ proteins under normal conditions, while downregulating osmotic stress-related regulatory genes under osmotic stress, in comparison to the wild type. Further analysis revealed that overexpressing OsNF-YB12 promoted JA biosynthesis and inhibit seed germination. Haplotype analysis suggested that OsNF-YB12 may have been selected during the differentiation of indica and japonica rice varieties. Therefore, this research provides a potential molecular target for exploring and harnessing the haplotype diversity of OsNF-YB12 to enhance yield stability under drought stress during rice domestication and improvement.

Rice Stripe Mosaic Virus Encoded P6 Interacts with Heading Protein OsHAPL1 to Promote Viral Infection

Rice stripe mosaic virus (RSMV) is the sole cytoplasmic rhabdovirus documented in naturally infected rice plants. It encodes P6, which induces delayed heading and reduces yield in infected rice plants. P6 of RSMV interacts with OsHAPL1, facilitating the interaction between OsHAPL1 and DTH8, resulting in delayed rice heading under long day conditions. Additionally, OsHAPL1 plays a dual role in RSMV infection by positively influencing viral infection while negatively regulating the expression of defense signal genes. These findings elucidate a novel molecular mechanism through which a virus manipulates the host defense system to enhance viral infection and transmission, shedding new light on the crosstalk between rice heading and disease resistance pathways.

The SLR1-OsMADS23-D14 module mediates the crosstalk between strigolactone and gibberellin signaling to control rice tillering

Strigolactones (SLs) and gibberellins (GAs) have been found to inhibit plant branching or tillering, but molecular mechanisms underlying the interplay between SL and GA signaling to modulate tillering remain elusive. We found that the transcription factor OsMADS23 plays a crucial role in the crosslink between SL and GA signaling in rice tillering. Loss-of-function mutant osmads23 shows normal axillary bud formation but defective bud outgrowth, thus reducing the tiller number in rice, whereas overexpression of OsMADS23 significantly increases tillering by promoting tiller bud outgrowth. OsMADS23 physically interacts with DELLA protein SLENDER RICE1 (SLR1), and the interaction reciprocally stabilizes each other. Genetic evidence showed that SLR1 is required for OsMADS23 to control rice tillering. OsMADS23 acts as an upstream transcriptional repressor to inhibit the expression of SL receptor gene DWARF14 (D14), and addition of SLR1 further enhances OsMADS23-mediated transcriptional repression of D14, indicating that D14 is the downstream target gene of OsMADS23-SLR1 complex. Moreover, application of exogenous SL and GA reduces the protein stability of OsMADS23-SLR1 complex and promotes D14 expression. Our results revealed that SLs and GAs synergistically inhibit rice tillering by destabilizing OsMADS23-SLR1 complex, which provides important insights into the molecular networks of SL-GA synergistic interaction during rice tillering.

Marker-Assisted Selection of Jacalin-Related Lectin Genes OsJRL45 and OsJRL40 Derived from Sea Rice 86 Enhances Salt Tolerance in Rice

Soil salinization limits rice growth and is an important restriction on grain yield. Jacalin-related lectins are involved in multiple stress responses, but their role in salt stress responses and use as molecular markers for salt tolerance remain poorly understood. Salt stress treatments and RT-qPCR analyses of Sea Rice 86 (SR86), 9311, and Nipponbare (Nip) showed that OsJRL45 and OsJRL40 enhanced tolerance of salt stress in SR86. Molecular markers based on sequence differences in SR86 and the salt-sensitive variety, 9311, in the intergenic region between OsJRL45 and OsJRL40 were validated in recombinant inbred lines derived from SR86 and 9311, hybrid populations, and common rice varieties. Yeast two-hybrid and bimolecular fluorescence complementation demonstrated that OsJRL45 and OsJRL40 interacted. Co-transformation of Nip with OsJRL45 and OsJRL40 derived from SR86 had no effect on the mature phenotype in T2 plants; however, salt stress at the three-leaf stage led to significant increases in CAT, POD, SOD, and Pro contents, but reduced MDA content in transgenic plants. Transcriptomic analysis identified 834 differentially expressed genes in transgenic plants under salt stress. GO and KEGG enrichment analyses indicated that metabolic pathways related to antioxidant responses and osmotic balance were crucial for salt-stress tolerance. Thus, molecular markers based on nucleotide differences in OsJRL45 and OsJRL40 provide a novel method for identifying salt-tolerant rice varieties.

A pair of nuclear factor Y transcription factors act as positive regulators in jasmonate signaling and disease resistance in Arabidopsis

The plant hormone jasmonate (JA) regulates plant growth and immunity by orchestrating a genome-wide transcriptional reprogramming. In the resting stage, JASMONATE-ZIM DOMAIN (JAZ) proteins act as main repressors to regulate the expression of JA-responsive genes in the JA signaling pathway. However, the mechanisms underlying de-repression of JA-responsive genes in response to JA treatment remain elusive. Here, we report two nuclear factor Y transcription factors NF-YB2 and NF-YB3 (thereafter YB2 and YB3) play key roles in such de-repression in Arabidopsis. YB2 and YB3 function redundantly and positively regulate plant resistance against the necrotrophic pathogen Botrytis cinerea, which are specially required for transcriptional activation of a set of JA-responsive genes following inoculation. Furthermore, YB2 and YB3 modulated their expression through direct occupancy and interaction with histone demethylase Ref6 to remove repressive histone modifications. Moreover, YB2 and YB3 physically interacted with JAZ repressors and negatively modulated their abundance, which in turn attenuated the inhibition of JAZ proteins on the transcription of JA-responsive genes, thereby activating JA response and promoting disease resistance. Overall, our study reveals the positive regulators of YB2 and YB3 in JA signaling by positively regulating transcription of JA-responsive genes and negatively modulating the abundance of JAZ proteins.

An AP2/ERF transcription factor confers chilling tolerance in rice

Cold stress, a prominent adverse environmental factor, severely hinders rice growth and productivity. Unraveling the complex mechanisms governing chilling tolerance in rice is crucial for molecular breeding of cold-tolerant varieties. Here, we identify an APETALA2/Ethylene Responsive Factor (AP2/ERF) transcription factor, OsERF52, as a positive modulator in response to low temperatures. OsERF52 directly regulates the expression of C-Repeat Binding Factor (CBF) genes in rice. In addition, Osmotic Stress/ABA-Activated Protein Kinase 9-mediated phosphorylation of OsERF52 at S261 enhances its stability and interaction with Ideal Plant Architecture 1 and OsbHLH002/OsICE1. This collaborative activation leads to the expression of OsCBFs, thereby initiating the chilling response in rice. Notably, plants with base-edited OsERF52S261D-3HA exhibit enhanced chilling resistance without yield penalty. Our findings unveil the mechanism orchestrated by a regulatory framework involving a protein kinase and transcription factors from diverse families, offering potential genetic resources for developing chilling-tolerant rice varieties.

Soybean steroids improve crop abiotic stress tolerance and increase yield

Sterols have long been associated with diverse fields, such as cancer treatment, drug development, and plant growth; however, their underlying mechanisms and functions remain enigmatic. Here, we unveil a critical role played by a GmNF-YC9-mediated CCAAT-box transcription complex in modulating the steroid metabolism pathway within soybeans. Specifically, this complex directly activates squalene monooxygenase (GmSQE1), which is a rate-limiting enzyme in steroid synthesis. Our findings demonstrate that overexpression of either GmNF-YC9 or GmSQE1 significantly enhances soybean stress tolerance, while the inhibition of SQE weakens this tolerance. Field experiments conducted over two seasons further reveal increased yields per plant in both GmNF-YC9 and GmSQE1 overexpressing plants under drought stress conditions. This enhanced stress tolerance is attributed to the reduction of abiotic stress-induced cell oxidative damage. Transcriptome and metabolome analyses shed light on the upregulation of multiple sterol compounds, including fucosterol and soyasaponin II, in GmNF-YC9 and GmSQE1 overexpressing soybean plants under stress conditions. Intriguingly, the application of soybean steroids, including fucosterol and soyasaponin II, significantly improves drought tolerance in soybean, wheat, foxtail millet, and maize. These findings underscore the pivotal role of soybean steroids in countering oxidative stress in plants and offer a new research strategy for enhancing crop stress tolerance and quality from gene regulation to chemical intervention.

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.

Molecular mechanisms underlying the signal perception and transduction during seed germination

QuerySeed germination is a vital step in the life cycle of a plant, playing a significant role in seedling establishment and crop yield potential. It is also an important factor in the conservation of plant germplasm resources. This complex process is influenced by a myriad of factors, including environmental conditions, the genetic makeup of the seed, and endogenous hormones. The perception of these environmental signals triggers a cascade of intricate signal transduction events that determine whether a seed germinates or remains dormant. Despite considerable progress in uncovering the molecular mechanisms governing these processes, many questions remain unanswered. In this review, we summarize the current progress in the molecular mechanisms underlying the perception of environmental signals and consequent signal transduction during seed germination, and discuss questions that need to be addressed to better understand the process of seed germination and develop novel strategies for germplasm improvement.

Genome-wide association studies identified OsTMF as a gene regulating rice seed germination under salt stress

Introduction

Salt tolerance during seed germination is an important trait for direct seeding and low-cost rice production. Nevertheless, it is still not clear how seed germination under salt stress is regulated genetically.

Methods

In this study, genome-wide association studies (GWAS) were performed to decipher the genetic basis of seed germination under salt stress using 541 rice varieties collected worldwide.

Results and discussion

Three quantitative trait loci (QTLs) were identified including qGRG3-1 on chromosome 3, qGRG3-2 on chromosome 5, and qGRG4 on chromosome 4. Assessment of candidate genes in these loci for their responses to salt stress identified a TATA modulatory factor (OsTMF) in qGRG3-2. The expression of OsTMF was up-regulated in both roots and shoots after exposure to salt stress, and OsTMF knockout mutants exhibited delayed seed germination under salt stress. Haplotype analysis showed that rice varieties carrying OsTMF-Hap2 displayed elevated salt tolerance during seed germination. These results provide important knowledge and resources to improve rice seed germination under salt stress in the future.