Defense-related Genes Research Articles

Overexpression of the First Peanut-Susceptible Gene, AhS5H1 or AhS5H2, Enhanced Susceptibility to Pst DC3000 in Arabidopsis.

Salicylic acid (SA) serves as a pivotal plant hormone involved in regulating plant defense mechanisms against biotic stresses, but the extent of its biological significance in relation to peanut resistance is currently lacking. This study elucidated the involvement of salicylic acid (SA) in conferring broad-spectrum disease resistance in peanuts through the experimental approach of inoculating SA-treated leaves. In several other plants, the salicylate hydroxylase genes are the typical susceptible genes (S genes). Here, we characterized two SA hydroxylase genes (AhS5H1 and AhS5H2) as the first S genes in peanut. Recombinant AhS5H proteins catalyzed SA in vitro, and showed SA 5-ydroxylase (S5H) activity. Overexpression of AhS5H1 or AhS5H2 decreased SA content and increased 2,5-DHBA levels in Arabidopsis, suggesting that both enzymes had a similar role in planta. Moreover, overexpression of each AhS5H gene increased susceptibility to Pst DC3000. Analysis of the transcript levels of defense-related genes indicated that the expression of AhS5H genes, AhNPR1 and AhPR10 was simultaneously induced by chitin. Overexpression of each AhS5H in Arabidopsis abolished the induction of AtPR1 or AtPR2 upon chitin treatment. Eventually, AhS5H2 expression levels were highly correlated with SA content in different tissues of peanut. Hence, the expression of AhS5H1 and AhS5H2 was tissue-specific.

RECOMBINANT PROTEIN APPLICATION INDUCED DEFENSE MECHANISM IN HOST PLANT AGAINST PAPAYA DIEBACK DISEASE

Erwinia mallotivora is a Gram-negative bacterium that causes the papaya dieback disease in Malaysia. Currently, no effective disease control method is documented. In this regard, the adoption of harpin proteins in promoting plant defense mechanisms has been reported to be a promising control method for this disease. This study used, two recombinant harpin proteins, Hrp I and Hrp II, to control the disease in the glasshouse and field conditions. The results of foliar application in the glasshouse showed protective index of 70.8% and 35.7% for Hrp I and Hrp II, respectively. Meanwhile, the field trial for Hrp I showed a promising protection index of 72.3%. Moreover, the plant growth-promoting attributes were also significantly improved in the case of the Hrp I -treated plants. The effectiveness of Hrp I and II as inducers of systemic acquired resistance (SAR) was further validated by profiling defense-related genes using RT-qPCR analysis. The results showed that the treated papaya plants with Hrp I possess the highest expression of defense genes such as peroxidase, osmotin, and PRID in the glasshouse and field samples. In conclusion, the application of Hrp I is a promising disease control approach in managing papaya dieback disease in Malaysia.

Pseudomonas aeruginosa LasI-dependent plant growth promotion requires the host nitrate transceptor AtNRT1.1/CHL1 and the nitrate reductases NIA1 and NIA2.

In P. aeruginosa, mutation of the gene encoding N-acyl-L-homoserine lactone synthase LasI drives defense and plant growth promotion, and this latter trait requires adequate nitrate nutrition. Cross-kingdom communication with bacteria is crucial for plant growth and productivity. Here, we show a strong induction of genes for nitrate uptake and assimilation in Arabidopsis seedlings co-cultivated with P. aeruginosa WT (PAO1) or ΔlasI mutants defective on the synthesis of the quorum-sensing signaling molecule N-(3-oxododecanoyl)-L-homoserine lactone. Along with differential induction of defense-related genes, the change from plant growth repression to growth promotion upon bacterial QS disruption, correlated with upregulation of the dual-affinity nitrate transceptor CHL1/AtNRT1/NPF6.3 and the nitrate reductases NIA1 and NIA2. CHL1-GUS was induced in Arabidopsis primary root tips after transfer onto P. aeruginosa ΔlasI streaks at low and high N availability, whereas this bacterium required high concentrations of nitrogen to potentiate root and shoot biomass production and to improve root branching. Arabidopsis chl1-5 and chl1-12 mutants and double mutants in NIA1 and NIA2 nitrate reductases showed compromised growth under low nitrogen availability and failed to mount an effective growth promotion and root branching response even at high NH4NO3. WT P. aeruginosa PAO1 and P. aeruginosa ΔlasI mutant promoted the accumulation of nitric oxide (NO) in roots of both the WT and nia1nia2 double mutants, whereas NO donors SNP or SNAP did not improve growth or root branching in nia1nia2 double mutants with or without bacterial cocultivation. Thus, inoculation of Arabidopsis roots with P. aeruginosa drives gene expression for improved nitrogen acquisition and this macronutrient is critical for the plant growth-promoting effects upon disruption of the LasI quorum-sensing system.

Stripe rust effector Pst21674 compromises wheat resistance by targeting transcription factor TaASR3.

Pathogens compromise host defense responses by strategically secreting effector proteins. However, the molecular mechanisms by which effectors manipulate disease-resistance factors to evade host surveillance remain poorly understood. In this study, we characterized a Puccinia striiformis f. sp. tritici (Pst) effector Pst21674 with a signal peptide. Pst21674 was significantly upregulated during Pst infections in wheat (Triticum aestivum L.) and knocking down Pst21674 by host-induced gene silencing led to reduced Pst pathogenicity and restricted hyphal spread in wheat. Pst21674 interaction with the abscisic acid-, stress-, and ripening-induced protein TaASR3 was validated mainly in the nucleus. Size exclusion chromatography, bimolecular fluorescence complementation, and luciferase complementation imaging assays confirmed that TaASR3 could form a functional tetramer. Virus-induced gene silencing and overexpression demonstrated that TaASR3 contributes to wheat resistance to stripe rust by promoting accumulation of reactive oxygen species and cell death. Additionally, transcriptome analysis revealed that the expression of defense-related genes was regulated in transgenic wheat plants overexpressing TaASR3. Interaction between Pst21674 and TaASR3 interfered with the polymerization of TaASR3 and suppressed TaASR3-mediated transcriptional activation of defense-related genes. These results indicate that Pst21674 serves as an important virulence factor secreted into the host nucleus to impede wheat resistance to Pst, possibly by targeting and preventing polymerization of TaASR3.

A geraniol synthase regulates plant defense via alternative splicing in tea plants.

Geraniol is an important contributor to the pleasant floral scent of tea products and one of the most abundant aroma compounds in tea plants; however, its biosynthesis and physiological function in response to stress in tea plants remain unclear. The proteins encoded by the full-length terpene synthase (CsTPS1) and its alternative splicing isoform (CsTPS1-AS) could catalyze the formation of geraniol when GPP was used as a substrate in vitro, whereas the expression of CsTPS1-AS was only significantly induced by Colletotrichum gloeosporioides and Neopestalotiopsis sp. infection. Silencing of CsTPS1 and CsTPS1-AS resulted in a significant decrease of geraniol content in tea plants. The geraniol content and disease resistance of tea plants were compared when CsTPS1 and CsTPS1-AS were silenced. Down-regulation of the expression of CsTPS1-AS reduced the accumulation of geraniol, and the silenced tea plants exhibited greater susceptibility to pathogen infection than control plants. However, there was no significant difference observed in the geraniol content and pathogen resistance between CsTPS1-silenced plants and control plants in the tea plants infected with two pathogens. Further analysis showed that silencing of CsTPS1-AS led to a decrease in the expression of the defense-related genes PR1 and PR2 and SA pathway-related genes in tea plants, which increased the susceptibility of tea plants to pathogens infections. Both in vitro and in vivo results indicated that CsTPS1 is involved in the regulation of geraniol formation and plant defense via alternative splicing in tea plants. The results of this study provide new insights into geraniol biosynthesis and highlight the role of monoterpene synthases in modulating plant disease resistance via alternative splicing.

Systemic screening of Fusarium oxysporum candidate effectors reveals FoSSP17 that suppresses plant immunity and contributes to virulence

Fusarium oxysporum f. sp. cubense (Foc) causes Fusarium wilt of banana (Musa spp.), a notorious soil-borne vascular fungal disease threatening the global banana industry. Phytopathogens secrete effectors to suppress plant immunity. However, little is known about the effectors of Foc race 4 (Foc4). In this study, we built a streamlined screening system (candidate effector prediction, RNA-seq-based expression level analysis, and cell death manipulative activity assessment based on transient expression in Nicotiana benthamiana) to identify candidate virulence-related effectors. In total, 80 candidate effector genes (CEGs) differentially expressed during plant colonization were predicted; 12 out of 15 characterized CEGs, including FoSSP17, could suppress BAX-triggered programmed cell death (PCD) in N. benthamiana and were induced during the infection of plants. FoSSP17 encodes a novel protein conserved in the Fusarium genus. FoSSP17 gene deletion mutants were not affected in vegetative growth and conidiation but showed reduced virulence. Furthermore, the deletion mutants triggered higher expression levels of host defense-related genes including PR1, PR3, PR5, and PR10. Signal peptide activity assay and subcellular localization assay suggested that FoSSP17 is a conventional secretory protein that exerts cell-death-suppressive activity inside plant cells. In addition, FoSSP17 suppressed pattern-triggered immunity in plants by inhibiting reactive oxygen species (ROS) accumulation, reducing callose deposition, and suppressing the expression of NbLOX and NbERF1 genes related to jasmonic acid (JA)-pathway and ethylene (ET)-pathway, respectively. Overall, a systemic screening of Foc4 candidate effectors reveals that FoSSP17 contributes to the virulence of Foc4 and suppresses pattern-triggered immunity in plants.

Defence responses triggered during the plant-pathogen interaction between strawberry (Fragaria x ananassa) and Colletotrichum acutatum

Strawberry (Fragaria x ananassa Duch.) production is an important economic activity in Argentina. Anthracnose, caused by Colletotrichum spp., is the most destructive fungal disease for strawberry and causes a huge economic loss every year. The gene-regulatory networks and metabolic pathways involved in the interaction between Fragaria ananassa and Colletotrichum acutatum are poorly understood. Sixteen strawberry cultivars were characterized in a local strain, M11, of C. acutatum, and the results showed that the Camarosa and Pajaro cultivars were the most tolerant and susceptible, respectively. Metabolic, biochemical and molecular analyses were used to study pathogen and strawberry interaction. The results showed that (1) after being infected by the pathogen, the Camarosa cultivar showed early induction of stomatal closure, callose and lignin accumulation; (2) the metabolic profile of the Camarosa cv. infected by C. acutatum showed high levels of carbohydrate accumulation, while the Pajaro cv. was characterized by accumulation of amino acids and their derivatives; (3) the expression of defence-related genes was induced earlier in the Camarosa cv. The above results demonstrated that an early and complex network of defence responses is triggered in the tolerant cultivar (Camarosa cv.), when infected by C. acutatum. Altogether, these results led us to expand the boundaries of knowledge of the metabolic pathways and gene-regulatory networks involved in the interaction between strawberry and Colletotrichum acutatum.

GmTOC1b negatively regulates resistance to Soybean mosaic virus

Soybean (Glycine max) is a major oil and feed crop worldwide. Soybean mosaic virus (SMV) is a globally occurring disease that severely reduces the yield and quality of soybean. Here, we characterized the role of the clock gene TIMING OF CAB EXPRESSION 1b (GmTOC1b) in the resistance of soybean to SMV. Homozygous Gmtoc1b mutants exhibited increased tolerance to SMV strain SC3 due to the activation of programmed cell death triggered by a hypersensitive response. Transcriptome deep sequencing and RT-qPCR analysis suggested that GmTOC1b likely regulates the expression of target genes involved in the salicylic acid (SA) signaling pathway. GmTOC1b binds to the promoter of GmWRKY40, which encodes a protein that activates the expression of SA-mediated defense-related genes. Moreover, we revealed that the GmTOC1bH1 haplotype, which confers increased tolerance to SMV, was artificially selected in improved cultivars from the Northern and Huang-Huai regions of China. Our results therefore identify a previously unknown SMV resistance component that could be deployed in the molecular breeding of soybean to enhance SMV resistance.

Determination of the antibacterial effect of bee venom against rainbow trout pathogens and antibiotic resistance gene expression

Abstract Bee venom (BV) is a rich source of secondary metabolites from honeybees (Apis mellifera L.). It contains a variety of bioactive ingredients including peptides, proteins, enzymes, and volatile metabolites. This study investigated the antibacterial effects of the bee venom obtained from honey bees (Apis mellifera L.) against bacterial fish pathogens, such as Lactococcus garvieae (Lg1, Lg2, Lg3), Vibrio anguillarum (Va1, Va2, Va3), Yersinia ruckeri (Yr1, Yr2, Yr3), and Aeromonas hydrophila (Ah1, Ah2, Ah3) and the expression levels on the antibiotic resistance genes hly and fbp (hemolysin and fibronectin-binding prot) of them. It was determined that bee venom had an antibacterial effect against L. garvieae, L. anguillarum, and Y. ruckeri strains, while it had no effect only against Ah3 and Ah2 bacterial strains. As staded by the gene expression of hly (hemolysin) and fbp (fibronectin-binding protein), among the antibiotic resistance genes the effect levels of bee venom on bacterial species varied, although it affected antibiotic resistance and gene expression level in all bacteria. It was revealed that the expression level was the highest for V. anguillarum strains, whereas it was below the control group for L. garvieae. i.e the effect of bee venom on the resistance mechanism for L. garvieae was much less compared to V. anguillarum. Based on the results in the current study it could be concluded that applying bee venom to pathogenic bacteria that cause mortality in the aquaculture sector could induce the defense-related gene and change the broad-spectrum biocontrol activity at the molecular level.

Volatile linalool activates grapevine resistance against downy mildew with changes in the leaf metabolome

Volatile organic compounds (VOCs) are produced by plants in response to biotic and abiotic stimuli. In grapevine, volatile terpenoids are triggered by downy mildew infection (caused by Plasmopara viticola), suggesting their involvement in plant defense responses. In particular, linalool was detected in leaves of downy mildew-resistant genotypes, but no information is available on its involvement in the defense mechanisms against P. viticola. The aim of this study was to investigate the defense mechanisms activated by linalool in grapevine leaves against P. viticola and to identify metabolic changes associated with linalool-induced resistance. Linalool treatment reduced downy mildew severity on leaf disks of susceptible grapevines (cultivar Pinot noir) and stimulated callose deposition at the sites of P. viticola infection. Moreover, the upregulation of defense-related genes was found in linalool-treated leaf disks, indicating the activation of grapevine defense mechanisms of salicylic acid and jasmonic acid pathways. Linalool treatment caused changes in the leaf metabolome of mock-inoculated and P. viticola-inoculated samples at one and six days post inoculation, as revealed by ultra-high pressure liquid chromatography-electrospray ionization-high-resolution quadrupole time of flight-mass spectrometry. Pathway analysis of annotated features with significant increases and decreases in abundance revealed the reprogramming of amino acid, phenylpropanoid, and terpenoid metabolisms in response to linalool treatment and P. viticola inoculation. In particular, features with significant increases in abundance in linalool-treated samples mainly belonged to putative phenylpropanoids, putative terpenoids, putative lipids, and lipid-like compounds, including molecules possibly associated with plant defense against pathogens, such as 2-phenylethanol, 2,4-heptadienal, α-terpineol, citral, and geraniol. These results demonstrated that linalool induces grapevine resistance against downy mildew, acting as a signaling molecule for plant resistance induction.

Genome-wide identification of calmodulin-binding protein 60 gene family and function of SmCBP60A1 in eggplant response to salt stress

Calmodulin-binding protein 60 (CBP60) members are essential in plant response to pathogen attack, and growth and development. Salt stress is one of the main abiotic stress affecting growth, development, and production in plants. However, the functions of CBP60 gene family members in plant response to abiotic stresses, especial salt stress, are largely unknown. Herein, we identified 10 CBP60 members in the eggplant (Solanum melongena) genome (SmCBP60) and analyzed their corresponding sequences and structures to explore their expression patterns. Further analysis showed that all 10 SmCBP60 proteins located in nuclei in the epidermic cells of Nicotiana benthamiana leaves, and the transcript expression levels of SmCBP60s including SmCBP60A1, SmCBP60A3, SmCBP60C1, and SmCBP60C2 were significantly up-regulated in the root of eggplant treated with salt stress. The silencing of SmCBP60A1 by virus-induced gene silencing enhanced eggplant susceptibility to salt stress, accompanied by down-regulation of transcript expression levels of salt stress defense-related marker genes Dehydrin 1 (SmDHN1), SmABA8’HO, SmDHNX1, and SmGSTU10, and decreased the content of proline and catalase (CAT) enzyme activity. These results suggest that SmCBP60A1 acts as a positive regulator in eggplant response to salt stress, and may be valuable for the improvement of eggplant varieties to improve its tolerance to salt stress.

Enhancing defense against rice blast disease: Unveiling the role of leaf endophytic firmicutes in antifungal antibiosis and induced systemic resistance

Rice remains the primary staple for more than half of the world's population, yet its cultivation faces numerous challenges, including both biotic and abiotic stresses. One significant obstacle is the prevalence of rice blast disease, which substantially diminishes productivity and increases cultivation costs due to frequent fungicide applications. Consequently, the presence of fungicide residues in rice raises concerns about compliance with international maximum residue limits (MRLs). While host resistance has proven effective, it often remains vulnerable to new variants of the Magnaporthe oryzae pathogen. Therefore, there is a critical need to explore innovative management strategies that can complement or enhance existing methods. An unexplored avenue involves harnessing endophytic bacterial communities. To this end, the present study investigates the potential of eleven endophytic Bacillus spp. in suppressing Pyricularia oryzae, promoting plant growth, and eliciting a defense response through phyllobacterization. The results indicate that the secreted metabolome and volatilome of seven tested isolates demonstrate inhibitory effects against P.oryzae, ranging from a minimum of 40% to a maximum of 70%. Bacillus siamensis L34, B. amyloliquefaciens RA37, B. velezensis L12, and B. subtilis B18 produce antifungal antibiotics targeting P.oryzae. Additionally, B. subtilis S4 and B. subtilis S6 emerge as excellent inducers of systemic resistance against blast disease, as evidenced by elevated activity of biochemical defense enzymes such as peroxidase, polyphenol oxidase, and total phenol content. However, a balance between primary metabolic activity (e.g., chlorophyll content, chlorophyll fluorescence, and photosynthetic rate) and defense activity is observed. Furthermore, specific endophytic Bacillus spp. significantly stimulates defense-related genes, including OsPAD4, OsFMO1, and OsEDS1. These findings underscore the multifaceted potential of endophytic Bacillus in managing blast disease through antibiosis and induced systemic resistance. In conclusion, this study highlights the promising role of endophytic Bacillus spp. as a viable option for blast disease management. Their ability to inhibit the pathogen and induce systemic resistance makes them a valuable addition to the existing strategies. However, it is crucial to consider the trade-off between primary metabolic activity and defense response when implementing these bacteria-based approaches.

NILR1 perceives a nematode ascaroside triggering immune signaling and resistance

Plants use pattern recognition receptors (PRRs) to perceive conserved molecular patterns derived from pathogens and pests, thereby activating a sequential set of rapid cellular immune responses, including activation of mitogen-activated protein kinases (MAPKs) and Ca2+-dependent protein kinases (CDPKs), transcriptional reprogramming (particularly the induction of defense-related genes), ion fluxes, and production of reactive oxygen species.1 Plant PRRs belong to the multi-membered protein families of receptor-like kinases (RLKs) or receptor-like proteins (RLPs). RLKs consist of a ligand-binding ectodomain, a single-pass transmembrane domain, and an intracellular kinase domain, while RLPs possess the same functional domains, except for the intracellular kinase domain.2 The most abundant nematode ascaroside, Ascr18, is a nematode-associated molecular pattern (NAMP) that induces immune signaling and enhances resistance to pathogens and pests in various plant species.3 In this study, we found that the Arabidopsis NEMATODE-INDUCED LRR-RLK1 (NILR1) protein4 physically interacts with the Ascr18 elicitor, as indicated by a specific direct interaction between NILR1 and Ascr18, and NILR1 is genetically required for Ascr18-triggered immune signaling and resistance to both bacterium and nematode, as manifested by the abolishment of these immune responses in the nilr1 mutant. These results suggest that NILR1 is the immune receptor of the nematode NAMP Ascr18, mediating Ascr18-triggered immune signaling and resistance to pathogens and pests.

Small RNAs contribute to citrus Huanglongbing tolerance by manipulating methyl salicylate signaling and exogenous methyl salicylate primes citrus groves from emerging infection.

Citrus production is severely threatened by the devastating Huanglongbing (HLB) disease globally. By studying and analyzing the defensive behaviors of an HLB-tolerant citrus cultivar 'Shatangju', we discovered that citrus can sense Candidatus Liberibacter asiaticus (CLas) infection and induce immune responses against HLB, which can be further strengthened by both endogenously produced and exogenously applied methyl salicylate (MeSA). This immune circuit is turned on by an miR2977-SAMT (encoding a citrus Salicylate [SA] O-methyltransferase) cascade, by which CLas infection leads to more in planta MeSA production and aerial emission. We provided both transgenic and multi-year trail evidences that MeSA is an effective community immune signal. Ambient MeSA accumulation and foliage application can effectively induce defense gene expression and significantly boost citrus performance. We also found that miRNAs are battle fields between citrus and CLas, and about 30% of the differential gene expression upon CLas infection are regulated by miRNAs. Furthermore, CLas hijacks host key processes by manipulating key citrus miRNAs, and citrus employs miRNAs that coordinately regulate defense-related genes. Based on our results, we proposed that miRNAs and associated components are key targets for engineering or breeding resistant citrus varieties. We anticipate that MeSA-based management, either induced expression or external application, would be a promising tool for HLB control.

LysM-mediated signaling in Marchantia polymorpha highlights the conservation of pattern-triggered immunity in land plants

Pattern-recognition receptor (PRR)-triggered immunity (PTI) wards off a wide range of pathogenic microbes, playing a pivotal role in angiosperms. The model liverwort Marchantia polymorpha triggers defense-related gene expression upon sensing components of bacterial and fungal extracts, suggesting the existence of PTI in this plant model. However, the molecular components of the putative PTI in M.polymorpha and the significance of PTI in bryophytes have not yet been described. We here show that M.polymorpha has four lysin motif (LysM)-domain-containing receptor homologs, two of which, LysM-receptor-like kinase (LYK) MpLYK1 and LYK-related (LYR) MpLYR, are responsible for sensing chitin and peptidoglycan fragments, triggering a series of characteristic immune responses. Comprehensive phosphoproteomic analysis of M.polymorpha in response to chitin treatment identified regulatory proteins that potentially shape LysM-mediated PTI. The identified proteins included homologs of well-described PTI components in angiosperms as well as proteins whose roles in PTI are not yet determined, including the blue-light receptor phototropin MpPHOT. We revealed that MpPHOT is required for negative feedback of defense-related gene expression during PTI. Taken together, this study outlines the basic framework of LysM-mediated PTI in M.polymorpha and highlights conserved elements and new aspects of pattern-triggered immunity in land plants.

MHP1 and MHL generate odd-chain fatty acids from 2-hydroxy fatty acids in sphingolipids and are related to immunity in Arabidopsis thaliana

In plants, the 2-hydroxy fatty acids (HFAs) of sphingolipids are important for plant growth and stress responses. Although the synthetic pathway of HFAs is well understood, their degradation has not yet been elucidated. In Saccharomyces cerevisiae, Mpo1 has been identified as a dioxygenase that degrades HFAs. This study examined the functions of two homologs of yeast Mpo1, MHP1 and MHL, in Arabidopsis thaliana. The mhp1 and mhp1mhl mutants showed a dwarf phenotype compared to that of the wild type. Lipid analysis of the mutants revealed the involvement of MHP1 and MHL in synthesizing odd-chain fatty acids (OCFAs), possibly by the degradation of HFAs. OCFAs are present in trace amounts in plants; however, their physiological significance is largely unknown. RNA sequence analysis of the mhp1mhl mutant revealed that growth-related genes decreased, whereas genes involved in stress response increased. Additionally, the mhp1mhl mutant had increased expression of defense-related genes and increased resistance to infection by Pseudomonas syringae pv. tomato DC3000 (Pto), and Pto carrying the effector AvrRpt2. Phytohormone analysis demonstrated that jasmonic acid in mhp1mhl was higher than that in the wild type. These results indicate that MHP1 and MHL are involved in synthesizing OCFAs and immunity in Arabidopsis.

SET Domain Group 703 Regulates Planthopper Resistance by Suppressing the Expression of Defense-Related Genes.

Plant defense responses against insect pests are intricately regulated by highly complex regulatory networks. Post-translational modifications (PTMs) of histones modulate the expression of genes involved in various biological processes. However, the role of PTMs in conferring insect resistance remains unclear. Through the screening of a T-DNA insertion activation-tagged mutant collection in rice, we identified the mutant planthopper susceptible 1 (phs1), which exhibits heightened expression of SET domain group 703 (SDG703). This overexpression is associated with increased susceptibility to the small brown planthopper (SBPH), an economically significant insect pest affecting rice crops. SDG703 is constitutively expressed in multiple tissues and shows substantial upregulation in response to SBPH feeding. SDG703 demonstrates the activity of histone H3K9 methyltransferase. Transcriptomic analysis revealed the downregulation of genes involved in effector-triggered immunity (ETI) and pattern-triggered immunity (PTI) in plants overexpressing SDG703. Among the downregulated genes, the overexpression of SDG703 in plants resulted in a higher level of histone H3K9 methylation compared to control plants. Collectively, these findings indicate that SDG703 suppresses the expression of defense-related genes through the promotion of histone methylation, consequently leading to reduced resistance against SBPH. The defense-related genes regulated by histone methylation present valuable targets for developing effective pest management strategies in future studies. Furthermore, our study provides novel insight into the epigenetic regulation involved in plant-insect resistance.

Pangenome analysis provides insights into the genetic diversity, metabolic versatility, and evolution of the genus Flavobacterium.

Members of the genus Flavobacterium are widely distributed and produce various polysaccharide-degrading enzymes. Many species in the genus have been isolated and characterized. However, few studies have focused on marine isolates or fish pathogens, and in-depth genomic analyses, particularly comparative analyses of isolates from different habitat types, are lacking. Here, we isolated 20 strains of the genus from various environments in South Korea and sequenced their full-length genomes. Combined with published sequence data, we examined genomic traits, evolution, environmental adaptation, and putative metabolic functions in total 187 genomes of isolated species in Flavobacterium categorized as marine, host-associated, and terrestrial including freshwater. A pangenome analysis revealed a correlation between genome size and coding or noncoding density. Flavobacterium spp. had high levels of diversity, allowing for novel gene repertories via recombination events. Defense-related genes only accounted for approximately 3% of predicted genes in all Flavobacterium genomes. While genes involved in metabolic pathways did not differ with respect to isolation source, there was substantial variation in genomic traits; in particular, the abundances of tRNAs and rRNAs were higher in the host-associdated group than in other groups. One genome in the host-associated group contained a Microviridae prophage closely related to an enterobacteria phage. The proteorhodopsin gene was only identified in four terrestrial strains isolated for this study. Furthermore, recombination events clearly influenced genomic diversity and may contribute to the response to environmental stress. These findings shed light on the high genetic variation in Flavobacterium and functional roles in diverse ecosystems as a result of their metabolic versatility. IMPORTANCE The genus Flavobacterium is a diverse group of bacteria that are found in a variety of environments. While most species of this genus are harmless and utilize organic substrates such as proteins and polysaccharides, some members may play a significant role in the cycling for organic substances within their environments. Nevertheless, little is known about the genomic dynamics and/or metabolic capacity of Flavobacterium. Here, we found that Flavobacterium species may have an open pangenome, containing a variety of diverse and novel gene repertoires. Intriguingly, we discovered that one genome (classified into host-associated group) contained a Microviridae prophage closely related to that of enterobacteria. Proteorhodopsin may be expressed under conditions of light or oxygen pressure in some strains isolated for this study. Our findings significantly contribute to the understanding of the members of the genus Flavobacterium diversity exploration and will provide a framework for the way for future ecological characterizations.

Early and Late Transcriptomic and Metabolomic Responses of Rhododendron 'Xiaotaohong' Petals to Infection with Alternaria sp.

In recent years, petal blight disease caused by pathogens has become increasingly epidemic in Rhododendron. Breeding disease-resistant rhododendron is considered to be a more environmentally friendly strategy than is the use of chemical reagents. In this study, we aimed to investigate the response mechanisms of rhododendron varieties to petal blight, using transcriptomics and metabolomics analyses. Specifically, we monitored changes in gene expression and metabolite accumulation in Rhododendron 'Xiaotaohong' petals infected with the Alternaria sp. strain (MR-9). The infection of MR-9 led to the development of petal blight and induced significant changes in gene transcription. Differentially expressed genes (DEGs) were predominantly enriched in the plant-pathogen interaction pathway. These DEGs were involved in carrying out stress responses, with genes associated with H2O2 production being up-regulated during the early and late stages of infection. Correspondingly, H2O2 accumulation was detected in the vicinity of the blight lesions. In addition, defense-related genes, including PR and FRK, exhibited significant up-regulated expression during the infection by MR-9. In the late stage of the infection, we also observed significant changes in differentially abundant metabolites (DAMs), including flavonoids, alkaloids, phenols, and terpenes. Notably, the levels of euscaphic acid, ganoderol A, (-)-cinchonidine, and theophylline in infected petals were 21.8, 8.5, 4.5, and 4.3 times higher, respectively, compared to the control. Our results suggest that H2O2, defense-related genes, and DAM accumulation are involved in the complex response mechanisms of Rhododendron 'Xiaotaohong' petals to MR-9 infection. These insights provide a deeper understanding of the pathogenesis of petal blight disease and may have practical implications for developing disease-resistant rhododendron varieties.

Defense-related gene expression in response to the application of biological control agents in banana

Black Sigatoka, caused by P. fijiensis, is the most important banana disease in Latin America as increasing applications of chemical fungicides used for its management result in both higher banana production costs and pathogen resistance. Spores of Bacillus subtilis, a proprietary Trichoderma sp., and a biological fermentation product composed of Saccharomyces cerevisiae cell walls and copper sulfate, were applied separately to evaluate potential defense responses in banana plants. The leaves were artificially inoculated with the pathogen, and the biological control agents were applied to the soil to avoid direct antagonism with the pathogen. Significantly lower (P < 0.05) area under disease progress curve values were observed among all treated plants compared with the control, with the lowest value measured in the treatment with a 5 % (w/v) concentration of a yeast cell wall product. In a second trial, the same biological control agents were applied to banana plants at 5 % (w/v) concentration to determine the relative expression of defense-related genes. Higher relative expression (P < 0.05) of PR3 and PR9 was observed at 3 and 24 h after application in the plants treated with B. subtilis and Trichoderma sp., respectively. In the plants treated with the yeast cell wall product, higher relative expression (P < 0.05) of PR3 was measured 48 h after application. The findings indicate that plant defenses may be activated by the biological control agents.