Role In Plant-pathogen Interactions Research Articles

Non-Specific Lipid Transfer Protein StLTP6 Promotes Virus Infection by Inhibiting Jasmonic Acid Signalling Pathway in Response to PVS TGB1.

Plant viruses rely on host factors for successful infection. Non-specific lipid transfer proteins (nsLTPs) play critical roles in plant-pathogen interactions; however, their functions and underlying molecular mechanisms in viral infections remain largely unknown. Jasmonic acid (JA) is a crucial regulatory hormone in the process of plant resistance to viral infection. In this study, we screened and verified that StLTP6, a previously identified pro-viral factor, interacts with the silencing suppressor triple gene block1 (TGB1) of potato virus S (PVS). The PVS TGB1 induces the expression of StLTP6, and both co-localize in the cytoplasm. Furthermore, StLTP6 interacts with allene oxide cyclase and inhibits its accumulation, thereby suppressing JA synthesis and attenuating RNA silencing antiviral resistance. In summary, we elucidated the molecular mechanism by which PVS TGB1 interacts with StLTP6 to facilitate PVS infection. These findings broaden our understanding of the biological roles of nsLTPs and provide a new antiviral target for potato research.

Nuclear localization sequence of MoHTR1, a Magnaporthe oryzae effector, for transcriptional reprogramming of immunity genes in rice

Plant pathogens secrete nuclear effectors into the host nuclei to modulate the host immune system. Although several nuclear effectors of fungal pathogens have been recently reported, the molecular mechanism of NLS-associated transport vehicles of nuclear effectors and the roles of NLS in transcriptional reprogramming of host immunity genes remain enigmatic. We previously reported the MoHTR1, a nuclear effector of the rice blast fungus, Magnaporthe oryzae. MoHTR1 is translocated to rice nuclei but not in fungal nuclei. Here, we identify the core NLS (RxKK) responsible for MoHTR1’s nuclear localization. MoHTR1 is translocated in the host nucleus through interaction with rice importin α. MoHTR1 NLS empowers it to translocate the cytoplasmic effectors of M. oryzae into rice nuclei. Furthermore, other nuclear effector candidates of the blast pathogen and rice proteins which have RxKK also exhibit nuclear localization, highlighting the crucial role of RxKK in this process. We also unveil the importance of SUMOylation in the stability of MoHTR1 and translocation of MoHTR1 to host nuclei. Moreover, MoHTR1 NLS is essential for the pathogenicity of M. oryzae by reprogramming immunity-associated genes in the host. Our findings provide insights into the significance of plant-specific NLS on fungal nuclear effectors and its role in plant-pathogen interactions.

Phosphonates of Pectobacterium atrosepticum: Discovery and Role in Plant-Pathogen Interactions.

Many phytopathogens' gene products that contribute to plant-pathogen interactions remain unexplored. In one of the most harmful phytopathogenic bacterium Pectobacterium atrosepticum (Pba), phosphonate-related genes have been previously shown to be among the most upregulated following host plant colonization. However, phosphonates, compounds characterized by a carbon-phosphorus bond in their composition, have not been described in Pectobacterium species and other phytopathogenic bacteria, with the exception of Pseudomonas syringae and Pantoea ananatis. Our study aimed to determine whether Pba synthesizes extracellular phosphonates and, if so, to analyze their physiological functions. We demonstrated that Pba produces two types of extracellular phosphonates: 2-diethoxyphosphorylethanamine and phenylphosphonic acid. Notably, such structures have not been previously described among natural phosphonates. The production of Pba phosphonates was shown to be positively regulated by quorum sensing and in the presence of pectic compounds. Pba phosphonates were found to have a positive effect on Pba stress resistance and a negative effect on Pba virulence. The discovered Pba phosphonates are discussed as metabolites that enable Pba to control its "harmful properties", thereby maintaining its ecological niche (the host plant) in a relatively functional state for an extended period.

Polyamines in Plant-Pathogen Interactions: Roles in Defense Mechanisms and Pathogenicity with Applications in Fungicide Development.

Polyamines (PAs), which are aliphatic polycationic compounds with a low molecular weight, are found in all living organisms and play essential roles in plant-pathogen interactions. Putrescine, spermidine, and spermine, the most common PAs in nature, respond to and function differently in plants and pathogens during their interactions. While plants use certain PAs to enhance their immunity, pathogens exploit PAs to facilitate successful invasion. In this review, we compile recent studies on the roles of PAs in plant-pathogen interactions, providing a comprehensive overview of their roles in both plant defense and pathogen pathogenicity. A thorough understanding of the functions of PAs and conjugated PAs highlights their potential applications in fungicide development. The creation of new fungicides and compounds derived from PAs demonstrates their promising potential for further research and innovation in this field.

Effector MoSDT1 enhances Magnaporthe oryzae virulence and plays a dual role in regulating rice defense.

C2H2 zinc effectors are a class of pathogen proteins that play a dual role in plant-pathogen interactions, promoting pathogenicity and enhancing plant defense. In our previous research, we identified Magnaporthe oryzae Systemic Defense Trigger 1 (MoSDT1) as a C2H2 zinc effector that activates rice (Oryza sativa) defense when overexpressed in rice. However, its regulatory roles in pathogenicity and defense require further investigation. In this study, we generated an MoSDT1 overexpressing strain and 2 knockout strains of M. oryzae to assess the impact of MoSDT1 on pathogenicity, rice defense, and phenotypic characteristics. Our analyses revealed that MoSDT1 substantially influenced vegetative growth, conidia size, and conidiation, and was crucial for the virulence of M. oryzae while suppressing rice defense. MoSDT1 localized to the nucleus and cytoplasm of rice, either dependent or independent of M. oryzae delivery. Through RNA-seq, scRNA-seq, and ChIP-seq, we identified that MoSDT1 modulates rice defense by regulating the phosphorylation and ubiquitination of various rice signaling proteins, including transcription factors, transcription repressors, kinases, phosphatases, and the ubiquitin system. These findings provide valuable insights into the regulatory mechanisms of C2H2 zinc finger effector proteins and offer important foundational information for utilizing their target genes in disease resistance breeding and the design of targets for disease management.

Lipids and Lipid-Mediated Signaling in Plant-Pathogen Interactions.

Plant lipids are essential cell constituents with many structural, storage, signaling, and defensive functions. During plant-pathogen interactions, lipids play parts in both the preexisting passive defense mechanisms and the pathogen-induced immune responses at the local and systemic levels. They interact with various components of the plant immune network and can modulate plant defense both positively and negatively. Under biotic stress, lipid signaling is mostly associated with oxygenated natural products derived from unsaturated fatty acids, known as oxylipins; among these, jasmonic acid has been of great interest as a specific mediator of plant defense against necrotrophic pathogens. Although numerous studies have documented the contribution of oxylipins and other lipid-derived species in plant immunity, their specific roles in plant-pathogen interactions and their involvement in the signaling network require further elucidation. This review presents the most relevant and recent studies on lipids and lipid-derived signaling molecules involved in plant-pathogen interactions, with the aim of providing a deeper insight into the mechanisms underpinning lipid-mediated regulation of the plant immune system.

Regulation of Disease-Resistance Genes against CWMV Infection by NbHAG1-Mediated H3K36ac.

Post-translational modification of proteins plays a critical role in plant-pathogen interactions. Here, we demonstrate in Nicotiana benthamiana that knockout of NbHAG1 promotes Chinese wheat mosaic virus (CWMV) infection, whereas NbHAG1 overexpression inhibits infection. Transcriptome sequencing indicated that a series of disease resistance-related genes were up-regulated after overexpression of NbHAG1. In addition, cleavage under targets and tagmentation (Cut&Tag)-qPCR results demonstrated that NbHAG1 may activate the transcription of its downstream disease-resistance genes by facilitating the acetylation level of H3K36ac. Therefore, we suggest that NbHAG1 is an important positive regulator of resistance to CWMV infestation.

Identification and characterization of the Remorin gene family in Saccharum and the involvement of ScREM1.5e-1/-2 in SCMV infection on sugarcane.

Remorins (REMs) are plant-specific membrane-associated proteins that play important roles in plant-pathogen interactions and environmental adaptations. Group I REMs are extensively involved in virus infection. However, little is known about the REM gene family in sugarcane (Saccharum spp. hyrid), the most important sugar and energy crop around world. Comparative genomics were employed to analyze the REM gene family in Saccharum spontaneum. Transcriptomics or RT-qPCR were used to analyze their expression files in different development stages or tissues under different treatments. Yeast two hybrid, bimolecular fluorescence complementation and co-immunoprecipitation assays were applied to investigate the protein interaction. In this study, 65 REMs were identified from Saccharum spontaneum genome and classified into six groups based on phylogenetic tree analysis. These REMs contain multiple cis-elements associated with growth, development, hormone and stress response. Expression profiling revealed that among different SsREMs with variable expression levels in different developmental stages or different tissues. A pair of alleles, ScREM1.5e-1/-2, were isolated from the sugarcane cultivar ROC22. ScREM1.5e-1/-2 were highly expressed in leaves, with the former expressed at significantly higher levels than the latter. Their expression was induced by treatment with H2O2, ABA, ethylene, brassinosteroid, SA or MeJA, and varied upon Sugarcane mosaic virus (SCMV) infection. ScREM1.5e-1 was localized to the plasma membrane (PM), while ScREM1.5e-2 was localized to the cytoplasm or nucleus. ScREM1.5e-1/-2 can self-interact and interact with each other, and interact with VPgs from SCMV, Sorghum mosaic virus, or Sugarcane streak mosaic virus. The interactions with VPgs relocated ScREM1.5e-1 from the PM to the cytoplasm. These results reveal the origin, distribution and evolution of the REM gene family in sugarcane and may shed light on engineering sugarcane resistance against sugarcane mosaic pathogens.

OsGELP77, a QTL for broad-spectrum disease resistance and yield in rice, encodes a GDSL-type lipase.

Lipids and lipid metabolites have essential roles in plant-pathogen interactions. GDSL-type lipases are involved in lipid metabolism modulating lipid homeostasis. Some plant GDSLs modulate lipid metabolism altering hormone signal transduction to regulate host-defence immunity. Here, we functionally characterized a rice lipase, OsGELP77, promoting both immunity and yield. OsGELP77 expression was induced by pathogen infection and jasmonic acid (JA) treatment. Overexpression of OsGELP77 enhanced rice resistance to both bacterial and fungal pathogens, while loss-of-function of osgelp77 showed susceptibility. OsGELP77 localizes to endoplasmic reticulum and is a functional lipase hydrolysing universal lipid substrates. Lipidomics analyses demonstrate that OsGELP77 is crucial for lipid metabolism and lipid-derived JA homeostasis. Genetic analyses confirm that OsGELP77-modulated resistance depends on JA signal transduction. Moreover, population genetic analyses indicate that OsGELP77 expression level is positively correlated with rice resistance against pathogens. Three haplotypes were classified based on nucleotide polymorphisms in the OsGELP77 promoter where OsGELP77Hap3 is an elite haplotype. Three OsGELP77 haplotypes are differentially distributed in wild and cultivated rice, while OsGELP77Hap3 has been broadly pyramided for hybrid rice development. Furthermore, quantitative trait locus (QTL) mapping and resistance evaluation of the constructed near-isogenic line validated OsGELP77, a QTL for broad-spectrum disease resistance. In addition, OsGELP77-modulated lipid metabolism promotes JA accumulation facilitating grain yield. Notably, the hub defence regulator OsWRKY45 acts upstream of OsGELP77 by initiating the JA-dependent signalling to trigger immunity. Together, OsGELP77, a QTL contributing to immunity and yield, is a candidate for breeding broad-spectrum resistant and high-yielding rice.

Characterization of heteropolysaccharides from Rhizoctonia solani AG1 IA cell wall and comparison of their effect on inducing plant defense

Rhizoctonia solani (R. solani) is an important pathogenic fungus that causes symptoms of sheath blight, and the polysaccharide-rich cell wall plays a major role in plant-pathogen interactions. However, the composition and structure of its cell wall polysaccharides are insufficiently understood, and its specific function in plant-pathogen interactions is unknown, which makes effective control of sheath blight difficult at present. Herein, five cell wall polysaccharides (WF-1, WF-2, CAF-1, HAF-1 and HAF 2-1) were sequentially extracted by boiling water, cold and hot alkali from R. solani AG1 IA. They were heteropolysaccharides containing mainly glucose, mannose and galactose and less fucose, with molecular weights above 1100 kDa. These five polysaccharides mainly composed of →4)-Glcp-(1→, →6)-Glcp-(1→, →4,6)-Glcp-(1→, →3,4)-Glcp-(1→, and Manp-(1→. Several polysaccharides, except WF-1, showed different induced resistance degrees on rice plant, with HAF 2-1 having the most significant effect. Further analysis using NMR confirmed that the backbone of HAF 2-1 mainly consisted of →4)-α-D-Glcp-(1→ and →6)-α-D-Glcp-(1→ with branches of →4,6)-D-Glcp-(1→. HAF 2-1 enhance the resistance of rice against R. solani through salicylic acid (SA)-mediated immune signaling pathway. This work improves our knowledge of the cell wall polysaccharides in plant pathogens and facilitates the study of pathogenic mechanisms and effective disease control.

Initial host invasion of Colletotrichum gloeosporioides is dampened by 1-methylcyclopropene due to blocking ethylene sensitivity of the fungus

Ethylene (ET) is not only a fruit ripening hormone, but also plays important roles in plant-pathogen interactions, as it is involved in both plant defense and fungal virulence. 1-methylcyclopropene (1-MCP) is a competitive inhibitor for ET being applied as a postharvest preservation agent to delay fruit ripening. Plant pathogenic fungi can also sense ET to promote fungal conidial germination, appressorium development, and pathogenicity. However, it is unclear whether 1-MCP could regulate postharvest disease development by interfering with the ET-sensing in pathogenic fungi. In this study, we identified the effects of ET and 1-MCP on the growth and development of Colletotrichum gloeosporioides, a fungal pathogen that causes anthracnose disease in various crops, and explored the regulatory effects of 1-MCP on the pathogenic fungus during its host invasions. The results showed that 1-MCP can inhibit the ET responses of C. gloeosporioides, including the ET-induced conidial germination, appressorium formation, and expression of the ethylene-responsive marker gene. Further analysis revealed that 1-MCP treatment dampened the host invasion of the fungus, and thus decreased disease severity on lime and strawberry fruit. Collectively, this study reveals the action mode of 1-MCP in inhibiting the fungal ET sensitivity and highlights the unexplored potential of using 1-MCP as a postharvest treatment to control postharvest diseases caused by fungal pathogens.

Effects of Intermittent Temperature and Humidity Regulation on Tomato Gray Mold.

Temperature and humidity play an important role in plant-pathogen interactions. However, regulating the temperature and humidity specifically to inhibit the development of plant diseases remains unclear. In this study, we explored the influence of intermittent temperature and humidity variation on tomato gray mold. Intermittent regulation of temperature and humidity (increasing temperature with decreasing humidity for different periods within 24 h) inhibited the disease severity of plants and the infection process of Botrytis cinerea. The 4-h treatment (increasing temperature accompanied by decreasing humidity for 4 h and recovering for 4 h, and so on) effectively inhibited the development of tomato gray mold, reduced the biomass of B. cinerea, delayed the differentiation time of mycelia, and inhibited the accumulation of hydrogen peroxide in tomato leaves at the later stage of infection. The increased expressions of heat-shock protein (HSP) genes HSP20, HSP70, HSP90, BAG6, and BAG7 in tomato were mainly caused by environmental changes and environment-plant-pathogen interactions, and the increased expression of the latter was greater than that of the former in the 2-h (increasing temperature accompanied by decreasing humidity for 2 h and recovering for 2 h, and so on) and 4-h treatments. Pathogen infection induced the expression of defense-related genes in tomato, and the increase in the expressions of FLS2, FEI1, PI2, Pti5, and WRKY75 induced by B. cinerea in the 4-h treatment was greater than that under unregulated temperature and humidity conditions. In general, intermittent temperature and humidity variation can effectively inhibit the development of tomato gray mold, and the 4-h treatment had the best inhibitory effect.

Genome-wide identification of papain-like cysteine proteases in Citrus sinensis and expression analysis in response to Candidatus Liberibacter asiaticus

ABSTRACT Papain-like cysteine proteases (PLCPs) play important roles in plant-pathogen interactions. In citrus, PLCPs are targeted by effectors from Candidatus Liberibacter asiaticus (CLas), the causal agent of Huanglongbing (HLB). To study interactions between Citrus sinensis and CLas, we identified 33 candidate CsPLCP genes by HMMsearch with the Peptidase_C1 domain (PF00112), and further confirmed them using local BLAST with PLCP sequences from Arabidopsis thaliana. The 33 CsPLCPs were classified into 9 subfamilies. Analysis of the cis-acting elements in their promoters indicated that CsPLCPs are responsive to various phytohormones and stressors. Further qPCR analysis indicated that several CsPLCPs were up-regulated during CLas infection. Subcellular localization analysis indicated that five CsPLCPs were localized to the cytoplasm and nucleus, while CsXBCP2 was localized only to the cytoplasm. In summary, this study provides a sound basis for understanding the roles of CsPLCPs in the Citrus-CLas interaction.

Drought stress-mediated differences in phyllosphere microbiome and associated pathogen resistance between male and female poplars.

Phyllosphere-associated microbes play a crucial role in plant-pathogen interactions while their composition and diversity are strongly influenced by drought stress. As dioecious plant species exhibited secondary dimorphism between the two sexes in response to drought stress, whether such difference will lead to sex-specific differences in phyllosphere microbiome and associated pathogen resistance between male and female conspecifics is still unknown. In this study, we subjected female and male full siblings of a dioecious poplar species to a short period of drought treatment followed by artificial infection of a leaf pathogenic fungus. Our results showed that male plants grew better than females with or without drought stress. Female control plants had more leaf lesion area than males after pathogen infection, whereas drought stress reversed such a difference. Further correlation and in vitro toxicity tests suggested that drought-mediated sexual differences in pathogen resistance between the two plant sexes could be attributed to the shifts in structure and function of phyllosphere-associated microbiome rather than the amount of leaf main defensive chemicals contained in plant leaves. Supportively, the microbiome analysis through high-throughput sequencing indicated that female phyllosphere enriched a higher abundance of ecologically beneficial microbes that serve as biological plant protectants, while males harbored abundant phytopathogens under drought-stressed conditions. The results could provide potential implications for the selection of suitable poplar sex to plants in drought or semi-drought habitats.

Cotton 4-coumarate-CoA ligase 3 enhanced plant resistance to Verticillium dahliae by promoting jasmonic acid signaling-mediated vascular lignification and metabolic flux.

Lignins and their antimicrobial-related polymers cooperatively enhance plant resistance to pathogens. Several isoforms of 4-coumarate-coenzyme A ligases (4CLs) have been identified as indispensable enzymes involved in lignin and flavonoid biosynthetic pathways. However, their roles in plant-pathogen interaction are still poorly understood. This study uncovers the role of Gh4CL3 in cotton resistance to the vascular pathogen Verticillium dahliae. The cotton 4CL3-CRISPR/Cas9 mutant (CR4cl) exhibited high susceptibility to V. dahliae. This susceptibility was most probably due to the reduction in the total lignin content and the biosynthesis of several phenolic metabolites, e.g., rutin, catechin, scopoletin glucoside, and chlorogenic acid, along with jasmonic acid (JA) attenuation. These changes were coupled with a significant reduction in 4CL activity toward p-coumaric acid substrate, and it is likely that recombinant Gh4CL3 could specifically catalyze p-coumaric acid to form p-coumaroyl-coenzyme A. Thus, overexpression of Gh4CL3 (OE4CL) showed increasing 4CL activity that augmented phenolic precursors, cinnamic, p-coumaric, and sinapic acids, channeling into lignin and flavonoid biosyntheses and enhanced resistance to V. dahliae. Besides, Gh4CL3 overexpression activated JA signaling that instantly stimulated lignin deposition and metabolic flux in response to pathogen, which all established an efficient plant defense response system, and inhibited V. dahliae mycelium growth. Our results propose that Gh4CL3 acts as a positive regulator for cotton resistance against V. dahliae by promoting JA signaling-mediated enhanced cell wall rigidity and metabolic flux.

Intermittent changes in temperature and humidity repress gray mold in tomato.

Environmental temperature and humidity play a vital role in plant-pathogen interactions, which profoundly affect the occurrence of crop diseases. However, the specific methods and mechanisms through which intermittent changes in temperature and humidity mitigate plant diseases remain unclear. In this study, six temperature and humidity combinations were set, the disease severity of tomatoes, biomass of Botrytis cinerea were analyzed, and the infection process of pathogens was observed using an optical microscope. Furthermore, dual RNA-seq analysis was performed to explore the interactions between plants and pathogens. Results showed that the 24hpi-12h day (regulation was performed at 24hpi (hours post-inoculation) for 12h after inoculation during the day) treatment reduced the gray mold severity and biomass of B. cinerea in plants by the greatest amount and effectively inhibited the growth of mycelia. The 24hpi-12h day treatment induced the up-regulation of light reactions, photorespiration, and Calvin cycle-related genes in tomatoes, whereas fungal genes related to the biosynthesis of sesquiterpene botrydial and polyketide botcinic acid were downregulated. Overall, we identified the optimal combination of temperature and humidity changes to inhibit the development of tomato gray mold, and preliminarily explored the interactions between tomato and B. cinerea under temperature and humidity changes. This work has practical importance and provides a theoretical basis for the ecological control of plant diseases.

Fatty Acid Profiling of Grapevine Extracellular Compartment.

The apoplast is the plant compartment present between the plasma membrane and the cuticle, comprised of the cell wall and the extracellular spaces where the "secretomes" are released and where the apoplastic fluid circulates. Within the many functions attributed to this compartment, its role in plant-pathogen interactions is irrefutable. It is the major point where plant and pathogen secretomes come in contact and several plant and pathogenic secreted proteins and small molecules present in this compartment are already cataloged in the literature. In plant-pathogen interactions, fatty acids and lipid molecules were shown to play a crucial role in the activation of plant immunity; however, the lipid composition of the apoplast is still a black box. Most of the studies performed to understand apoplast dynamics have used proteomic-based techniques; however, knowledge about apoplastic proteins involved in lipid metabolism and transport is still severely limited. In grapevine, only three studies have been published so far focusing on the characterization of this compartment and only one of them deals with grapevine-pathogen interaction. Here we refer to our recently established method for grapevine leaves' apoplastic fluid isolation and describe a direct methylation protocol for the analysis of apoplastic fluid fatty acids. We also point out a novel intracellular marker that may be used to assess apoplastic fluid purity.

Genomic survey of NPF and NRT2 transporter gene families in five inbred maize lines and their responses to pathogens infection

Besides manipulating nitrate uptake and allocation, nitrate transporters (NRTs) are also known to play crucial roles in pathogen defense and stress response. By blasting with the model NRT genes of poplar and Arabidopsis, a total of 408 gene members were identified from 5 maize inbred lines in which the number of NRTs ranged from 72 to 88. Phylogenetic analysis showed that the NRT genes of maize were classified into NRT1/PTR (NPF), NRT2 and NRT3 subfamilies, respectively. Marked divergence of the duplication patterns of NRT genes were identified, which may be a new basis for classification and identification of maize varieties. In terms of biotic stress, NRT2.5A showed an enhanced expression during the pathogen infection of Colletotrichum graminicola, while NRT1c4C was down-regulated, suggesting that maize NRT transporters may have both positive and negative roles in the disease resistance response. This work will promote the further studies of NRT gene families in maize, as well as be beneficial for further understanding of their potential roles in plant-pathogen interactions.

A new in vitro monitoring system reveals a specific influence of Arabidopsis nitrogen nutrition on its susceptibility to Alternaria brassicicola at the seedling stage.

Seedling growth is an early phase of plant development highly susceptible to environmental factors such as soil nitrogen (N) availability or presence of seed-borne pathogens. Whereas N plays a central role in plant-pathogen interactions, its role has never been studied during this early phase for the interaction between Arabidopsis thaliana and Alternaria brassicicola, a seed-transmitted necrotrophic fungus. The aim of the present work was to develop an in vitro monitoring system allowing to study the impact of the fungus on A. thaliana seedling growth, while modulating N nutrition. The developed system consists of square plates placed vertically and filled with nutrient agar medium allowing modulation of N conditions. Seeds are inoculated after sowing by depositing a droplet of conidial suspension. A specific semi-automated image analysis pipeline based on the Ilastik software was developed to quantify the impact of the fungus on seedling aerial development, calculating an index accounting for every aspect of fungal impact, namely seedling death, necrosis and developmental delay. The system also permits to monitor root elongation. The interest of the system was then confirmed by characterising how N media composition [0.1 and 5mM of nitrate (NO3-), 5mM of ammonium (NH4+)] affects the impact of the fungus on three A. thaliana ecotypes. Seedling development was strongly and negatively affected by the fungus. However, seedlings grown with 5mM NO3- were less susceptible than those grown with NH4+ or 0.1mM NO3-, which differed from what was observed with adult plants (rosette stage). The developed monitoring system allows accurate determination of seedling growth characteristics (both on aerial and root parts) and symptoms. Altogether, this system could be used to study the impact of plant nutrition on susceptibility of various genotypes to fungi at the seedling stage.

Sparking a sulfur war between plants and pathogens.

The biochemical versatility of sulfur (S) lends itself to myriad roles in plant-pathogen interactions. This review evaluates the current understanding of mechanisms by which pathogens acquire S from their plant hosts and highlights new evidence that plants can limit S availability during the immune responses. We discuss the discovery of host disease-susceptibility genes related to S that can be genetically manipulated to create new crop resistance. Finally, we summarize future research challenges and propose a research agenda that leverages systems biology approaches for a holistic understanding of this important element's diverse roles in plant disease resistance and susceptibility.