Transcriptome analysis reveals the mechanism of zinc ion-mediated plant resistance to TMV in Nicotiana benthamiana

ETHYLENE RESPONSE FACTOR6, A Central Regulator of Plant Growth in Response to Stress

ETHYLENE RESPONSE FACTOR6 (ERF6) has emerged as a central player in stress-induced plant growth inhibition. It orchestrates complex pathways that enable plants to acclimate and thrive in challenging environments. In response to various abiotic and biotic stresses, ERF6 is promptly activated through both ethylene-dependent and -independent pathways, and contributes to enhanced stress tolerance mechanisms by activating a broad spectrum of genes at various developmental stages. Despite the crucial role of ERF6, there is currently a lack of published comprehensive insights into its function in plant growth and stress response. In this respect, based on the tight connection between ethylene and ERF6, we review the latest research findings on how ethylene regulates stress responses and the mechanisms involved. In addition, we summarize the trends and advances in ERF6-mediated plant performance under optimal and stressful conditions. Finally, we also highlight key questions and suggest potential paths to unravel the ERF6 regulon in future research.

A resilient mutualistic interaction between cucumber mosaic virus and its natural host to adapt to an excess zinc environment and drought stress

A perennial pseudometallophyte Arabidopsis halleri is frequently infected with cucumber mosaic virus (CMV) in its natural habitat. The purpose of this study was to characterize the effect of CMV infection on the environmental adaptation of its natural host A. halleri. The CMV(Ho) strain isolated from A. halleri was inoculated into clonal virus-free A. halleri plants, and a unique plant-virus system consisting of CMV(Ho) and its natural wild plant host was established. In a control environment with ambient zinc supplementation, CMV(Ho) infection retarded growth in the above-ground part of host plants but conferred strong drought tolerance. On the other hand, in an excess zinc environment, simulating a natural edaphic environment of A halleri, host plants hyperaccumulated zinc and CMV(Ho) infection did not cause any symptoms to host plants while conferring mild drought tolerance. We also demonstrated in Nicotiana benthamiana as another host that similar effects were induced by the combination of excess zinc and CMV(Ho) infection. Transcriptomic analysis indicated that the host plant recognized CMV(Ho) as a mutualistic symbiont rather than a parasitic pathogen. These results suggest a resilient mutualistic interaction between CMV(Ho) and its natural host A. halleri in its natural habitat.

Inhibition of Monilinia fructicola sporulation and pathogenicity through eucalyptol-mediated targeting of MfCat2 by Streptomyces lincolnensis strain JCP1-7

Peach brown rot, attributed to Monilinia fructicola, presents a significant threat to postharvest peach cultivation, causing losses of up to 80%. With an increasing number of countries, spearheaded by the European Union, imposing bans on chemical agents in fruit production, there is a growing interest in mining highly active antibacterial compounds from biological control strains for postharvest disease management. In this study, we highlight the unique ability of Streptomyces lincolnensis strain JCP1-7 to inhibit M. fructicola sporulation, despite its limited antimicrobial efficacy. Through GC-MS analysis, eucalyptol was identified as the key compound. Fumigation of diseased fruits with eucalyptol at a concentration of 0.0335 μg cm-3 demonstrated an in vivo inhibition rate against M. fructicola of 93.13%, completely suppressing spore formation. Transcriptome analysis revealed the impact of eucalyptol on multiple pathogenesis-related pathways, particularly through the inhibition of catalase 2 (Cat2) expression. Experiments with a MfCat2 knockout strain (ΔMfCat2) showed reduced pathogenicity and sensitivity to JCP1-7 and eucalyptol, suggesting MfCat2 as a potential target of JCP1-7 and eucalyptol against M. fructicola. Our findings elucidate that eucalyptol produced by S. lincolnensis JCP1-7 inhibits M. fructicola sporulation by regulating MfCat2, thereby effectively reducing postharvest peach brown rot occurrence. The use of fumigation of eucalyptol offers insights into peach brown rot management on a large scale, thus making a significant contribution to agricultural research.

Transcriptomics, proteomics, and metabolomics interventions prompt crop improvement against metal(loid) toxicity

The escalating challenges posed by metal(loid) toxicity in agricultural ecosystems, exacerbated by rapid climate change and anthropogenic pressures, demand urgent attention. Soil contamination is a critical issue because it significantly impacts crop productivity. The widespread threat of metal(loid) toxicity can jeopardize global food security due to contaminated food supplies and pose environmental risks, contributing to soil and water pollution and thus impacting the whole ecosystem. In this context, plants have evolved complex mechanisms to combat metal(loid) stress. Amid the array of innovative approaches, omics, notably transcriptomics, proteomics, and metabolomics, have emerged as transformative tools, shedding light on the genes, proteins, and key metabolites involved in metal(loid) stress responses and tolerance mechanisms. These identified candidates hold promise for developing high-yielding crops with desirable agronomic traits. Computational biology tools like bioinformatics, biological databases, and analytical pipelines support these omics approaches by harnessing diverse information and facilitating the mapping of genotype-to-phenotype relationships under stress conditions. This review explores: (1) the multifaceted strategies that plants use to adapt to metal(loid) toxicity in their environment; (2) the latest findings in metal(loid)-mediated transcriptomics, proteomics, and metabolomics studies across various plant species; (3) the integration of omics data with artificial intelligence and high-throughput phenotyping; (4) the latest bioinformatics databases, tools and pipelines for single and/or multi-omics data integration; (5) the latest insights into stress adaptations and tolerance mechanisms for future outlooks; and (6) the capacity of omics advances for creating sustainable and resilient crop plants that can thrive in metal(loid)-contaminated environments.

A high rain-erosion resistant bio-based nanogel with continuous immunity induction for plant virus inhibition

Tobacco mosaic virus (TMV) is the most widely spread and harmful virus in the world, causing serious economic losses annually. However, the low anti-erosion ability of the pesticides for TMV management make it easy to be washed by the rain, which makes the effective duration of the pesticides shorter. In this paper, a new bio-based nanogel with superior antiviral activity was reported, and its slow-release behavior, rain erosion resistance and the antiviral mechanism was systematically studied. The results determined that the nanogels (Zn2+@ALGNP and Zn2+@ALGNP@PL) exhibited sustained releasing of Zn2+ with a 7 days duration, and the ε-PL coating could enhance the releasing rate of Zn2+. Moreover, Zn2+@ALGNP@PL displayed a lower contact angle, indicating greater adhesion to the leaf surface, and in consequence imposed better resistance to simulate rain erosion than pure Zn2+. Strikingly, Zn2+@ALGNP@PL could inhibit plant virus infection by aggregating the virions and reducing its coat protein stability, as well as inducing the efficient expression of reactive oxygen species, antioxidant enzymes and resistance genes to enhance plant resistance and promote plant growth. Overall, this study had successfully developed a high rain-erosion resistant bio-based nanogel capable of continue to induce resistant plants and promote plant growth.

Role of bZIP Transcription Factors in Response to NaCl Stress in Tamarix ramosissima under Exogenous Potassium (K+)

Salt stress is a significant environmental factor affecting plant growth and development, with NaCl stress being one of the most common types of salt stress. The halophyte, Tamarix ramosissima Ledeb (T. ramosissima), is frequently utilized for the afforestation of saline-alkali soils. Indeed, there has been limited research and reports by experts and scholars on the regulatory mechanisms of basic leucine zipper (bZIP) genes in T. ramosissima when treated with exogenous potassium (K+) to alleviate the effects of NaCl stress. This study focused on the bZIP genes in T. ramosissima roots under NaCl stress with additional KCl applied. We identified key candidate genes and metabolic pathways related to bZIP and validated them through quantitative real-time PCR (qRT-PCR). The results revealed that under NaCl stress with additional KCl applied treatments at 0 h, 48 h, and 168 h, based on Pfam protein domain prediction and physicochemical property analysis, we identified 20 related bZIP genes. Notably, four bZIP genes (bZIP_2, bZIP_6, bZIP_16, and bZIP_18) were labeled with the plant hormone signal transduction pathway, showing a predominant up-regulation in expression levels. The results suggest that these genes may mediate multiple physiological pathways under NaCl stress with additional KCl applied at 48 h and 168 h, enhancing signal transduction, reducing the accumulation of ROS, and decreasing oxidative damage, thereby enhancing the tolerance of T. ramosissima to NaCl stress. This study provides gene resources and a theoretical basis for further breeding of salt-tolerant Tamarix species and the involvement of bZIP transcription factors in mitigating NaCl toxicity.

Synthesis of chitin nanocrystals supported Zn2+ with high activity against tobacco mosaic virus

Chitin is a kind of natural nitrogenous organic polysaccharide. It contains antibacterial and antiviral properties, and it can induce plant disease resistance and promote plant growth. However, its application is constrained due to its insolubility and intricate molecular structure. Tobacco mosaic disease is caused by tobacco mosaic virus (TMV) infection, which seriously harms tobacco production. Zinc-containing chemical agents are commonly used to control tobacco mosaic disease, but overuse of chemical agents will cause serious environmental pollution. In this study, a novel nanomaterial (ChNC@Zn) was prepared by using chitin nanocrystals loaded with Zn2+, which has the function of inducing disease resistance to plants and reducing virus activity. When the Zn2+ concentration of ChNC@Zn is 105.6 μg/mL, it shows higher resistance to TMV than Lentinan (LNT). ChNC@Zn can improve the enzymes activities of peroxidase (POD) and catalase (CAT) in tobacco, and reduce the damage of reactive oxygen species (ROS) caused by TMV infection, thereby inducing resistance to TMV in tobacco. Besides, it can promote the growth of tobacco. As a result, ChNC@Zn can exhibit strong antiviral activity at low Zn2+ concentration and minimize the pollution of Zn2+ to the environment, which has high potential application value in the control of virus disease.

Transcriptomic and functional analyses reveal the molecular mechanisms underlying Fe-mediated tobacco resistance to potato virus Y infection

Potato virus Y (PVY) mainly infects Solanaceous crops, resulting in considerable losses in the yield and quality. Iron (Fe) is involved in various biological processes in plants, but its roles in resistance to PVY infection has not been reported. In this study, foliar application of Fe could effectively inhibit early infection of PVY, and a full-length transcriptome and Illumina RNA sequencing was performed to investigate its modes of action in PVY-infected Nicotiana tabacum. The results showed that 18,074 alternative splicing variants, 3,654 fusion transcripts, 3,086 long non-coding RNAs and 14,403 differentially expressed genes (DEGs) were identified. Specifically, Fe application down-regulated the expression levels of the DEGs related to phospholipid hydrolysis, phospholipid signal, cell wall biosynthesis, transcription factors (TFs) and photosystem I composition, while those involved with photosynthetic electron transport chain (PETC) were up-regulated at 1 day post inoculation (dpi). At 3 dpi, these DEGs related to photosystem II composition, PETC, molecular chaperones, protein degradation and some TFs were up-regulated, while those associated with light-harvesting, phospholipid hydrolysis, cell wall biosynthesis were down-regulated. At 9 dpi, Fe application had little effects on resistance to PVY infection and transcript profiles. Functional analysis of these potentially critical DEGs was thereafter performed using virus-induced gene silencing approaches and the results showed that NbCat-6A positively regulates PVY infection, while the reduced expressions of NbWRKY26, NbnsLTP, NbFAD3 and NbHSP90 significantly promote PVY infection in N. benthamiana. Our results elucidated the regulatory network of Fe-mediated resistance to PVY infection in plants, and the functional candidate genes also provide important theoretical bases to further improve host resistance against PVY infection.

Reactive oxygen species-related genes participate in resistance to cucumber green mottle mosaic virus infection regulated by boron in Nicotiana benthamiana and watermelon

Cucumber green mottle mosaic virus (CGMMV) infection causes acidification and rot of watermelon flesh, resulting in serious economic losses. It is widely reported the interaction relationship between boron and reactive oxygen species (ROS) in regulating normal growth and disease resistance in plants. Our previous results demonstrated that exogenous boron could improve watermelon resistance to CGMMV infection. However, the roles of ROS-related genes regulated by boron in resistance to CGMMV infection are unclear. Here, we demonstrated that CGMMV symptoms were alleviated, and viral accumulations were decreased by boron application in Nicotiana benthamiana, indicating that boron contributed to inhibiting CGMMV infection. Meanwhile, we found that a number of differentially expressed genes (DEGs) associated with inositol biosynthesis, ethylene synthesis, Ca²⁺ signaling transduction and ROS scavenging system were up-regulated, while many DEGs involved in ABA catabolism, GA signal transduction and ascorbic acid metabolism were down-regulated by boron application under CGMMV infection. Additionally, we individually silenced nine ROS-related genes to explore their anti-CGMMV roles using a tobacco rattle virus (TRV) vector. The results showed that NbCat1, NbGME1, NbGGP and NbPrx Q were required for CGMMV infection, while NbGST and NbIPS played roles in resistance to CGMMV infection. The similar results were obtained in watermelon by silencing of ClCat, ClPrx or ClGST expression using a pV190 vector. This study proposed a new strategy for improving plant resistance to CGMMV infection by boron-regulated ROS pathway and provided several target genes for watermelon disease resistance breeding.