Expression and functional characterization of two pathogenesis-related protein 10 genes from Zea mays

Walnut PR10/Bet v1-like proteins interact with chitinase in response to anthracnose stress

Walnut is a significant woody oil tree species that has been increasingly affected by anthracnose in recent years. Effective anthracnose control is crucial for walnut yield and quality, which requires a comprehensive understanding of the response mechanisms to Colletotrichum gloeosporioides. The PR10/Bet v1-like proteins are involved in defense against various diseases, therefore, in this study, seven JrBet v1s were identified from the walnut transcriptome (named JrBet v1-1~1-7), whose open reading frame was 414~483 bp in length with isoelectric point ranging from 4.96 to 6.11. These JrBet v1s were classified into three groups, with the MLP/RRP and Dicot PR-10 subfamilies each comprising three members (the largest ones), indicating that the proteins within these two subfamilies may have evolved from a shared ancestral gene within the broader PR10/Bet v1 protein family. The cis-elements in the promoters of JrBet v1s were involved in response to hormones, coercive, and plant growth metabolism. Most JrBet v1s could be significantly upregulated by walnut anthracnose, JrBet v1-1, JrBet v1-2, JrBet v1-4, and JrBet v1-6 peaked at 12 days of anthracnose stress, showing a 2.85- to 63.12-fold increase compared to the control, while JrBet v1-3, JrBet v1-5 and JrBet v1-7 peaked at 9 days, with a 3.23- to 27.67-fold increase. Furthermore, the significant correlation of the upregulation under anthracnose stress of JrBet v1s and JrChit02-1 as well as JrChit02-2, the genes encoding chitinase, suggesting that during the long process of microevolution in walnut-C. gloeosporioides interactions, walnut has developed a Bet v1-chitinase defense mechanism to counteract pathogen invasion.

Impact of homologous overexpression of PR10a gene on improving salt stress tolerance in transgenic Solanum tuberosum

Abiotic stresses severely affected crop productivity and considered to be a major yield limiting factor for crop plant. The tolerance to these stresses is a very complex phenomenon involving a wide array of molecular, biochemical and physiological changes in plant cells. Therefore, it is challenging to understand the molecular basis of abiotic stress tolerance to manipulate it for improving abiotic stress tolerance of major crops. Biotechnological approaches and genetic engineering including homologous gene overexpression can be implemented to understand gene functions under well-defined conditions. The Pathogenesis-related proteins (PR10) such as PR10a play multiple roles in biotic and abiotic stress tolerance and, hence, plant development. A PR10a gene from potato cv. Deseree was introduced into three cultivars of potato (Solanum tuberosum L.) by Agrobacterium tumefaciens-mediated genetic transformation. Transgenic plants were selected on a medium containing 1.0 mg/l phosphinothricin (PPT) and confirmed by polymerase chain reaction (PCR), herbicide (BASTA®) leaf paint assay, and Real-Time- quantitative PCR analyses (qPCR). All of the selected transformants showed completely tolerance to the application of PPT application. Experiments designed for testing salt tolerance revealed that there was enhanced salt tolerance of the transgenic lines in vitro in terms of morphological (plant FW, plant DW and plant height) and antioxidant activates as compared to the non-transgenic control plants. qRT-PCR showed that the expression of PR10a gene in the transgenic potato is higher than that in non-transgenic control under salt stress. The relative PR10a gene-expression patterns in the transgenic plants shed lights into the molecular response of homologues overexpressed PR10a potato to salt-stress conditions. The obtained results provide insights on the fact that PR10a plays a major role regarding salt stress tolerance in potato plants.

The ZmCPK39-ZmDi19-ZmPR10 immune module regulates quantitative resistance to multiple foliar diseases in maize

Gray leaf spot, northern leaf blight and southern leaf blight are three of the most destructive foliar diseases affecting maize (Zea mays L.). Here we identified a gene, ZmCPK39, that encodes a calcium-dependent protein kinase and negatively regulates quantitative resistance to these three diseases. The ZmCPK39 allele in the resistant line displayed significantly lower pathogen-induced gene expression than that in the susceptible line. A marked decrease in ZmCPK39 abundance mitigated the phosphorylation and degradation of the transcription factor ZmDi19. This led to elevated expression of ZmPR10, a gene known to encode an antimicrobial protein, thereby enhancing maize resistance to foliar diseases. Moreover, the F1 hybrid with reduced ZmCPK39 expression favored disease resistance, thereby increasing yield. Hence, the discovery of the ZmCPK39-ZmDi19-ZmPR10 immune module provides insight into the mechanisms underlying broad-spectrum quantitative disease resistance and also offers a new avenue for the genetic control of maize foliar diseases.

Two transcription factors, RhERF005 and RhCCCH12, regulate rose resistance to Botrytis cinerea by modulating cytokinin levels

Gray mold caused by the necrotrophic fungal pathogen Botrytis cinerea is one of the most destructive diseases in rose (Rosa spp.). Rose infection by B. cinerea leads to severe economic losses due to necrosis, tissue collapse, and rot. In rose, cytokinins (CKs) positively regulate a defense response to B. cinerea, but little is known about the underlying molecular mechanisms. Here, we characterized two ethylene/jasmonic acid-regulated transcription factors, RhEFR005 and RhCCCH12, that bind to the promoter region of PATHOGENESIS-RELATED 10.1 (RhPR10.1) and promote its transcription, leading to decreased susceptibility to B. cinerea. The RhEFR005/RhCCCH12-RhPR10.1 module regulated cytokinin content in rose, and the susceptibility of RhEFR005-, RhCCCH12-, and RhPR10.1-silenced rose petals can be rescued by exogenous CK. In summary, our results reveal that the RhERF005/RhCCCH12-RhPR10.1 module regulates the CK-induced defense response of rose to B. cinerea.

Genome-wide identification of rubber tree pathogenesis-related 10 (PR-10) proteins with biological relevance to plant defense

Pathogenesis-related 10 (PR-10) is a group of small intracellular proteins that is one of 17 subclasses of pathogenesis-related proteins in plants. The PR-10 proteins have been studied extensively and are well-recognized for their contribution to host defense against phytopathogens in several plant species. Interestingly, the accumulation of PR-10 proteins in the rubber tree, one of the most economically important crops worldwide, after being infected by pathogenic organisms has only recently been reported. In this study, the homologous proteins of the PR-10 family were systemically identified from the recently available rubber tree genomes in the NCBI database. The sequence compositions, structural characteristics, protein physical properties, and phylogenetic relationships of identified PR-10 proteins in rubber trees support their classification into subgroups, which mainly consist of Pru ar 1-like major allergens and major latex-like (MLP) proteins. The rubber tree PR10-encoding genes were majorly clustered on chromosome 15. The potential roles of rubber tree PR-10 proteins are discussed based on previous reports. The homologous proteins in the PR-10 family were identified in the recent genomes of rubber trees and were shown to be crucial in host responses to biotic challenges. The genome-wide identification conducted here will accelerate the future study of rubber tree PR-10 proteins. A better understanding of these defense-related proteins may contribute to alternative ways of developing rubber tree clones with desirable traits in the future.

Pathogenesis-related protein 10 in resistance to biotic stress: progress in elucidating functions, regulation and modes of action

Introduction

The Family of pathogenesis-related proteins 10 (PR-10) is widely distributed in the plant kingdom. PR-10 are multifunctional proteins, constitutively expressed in all plant tissues, playing a role in growth and development or being induced in stress situations. Several studies have investigated the preponderant role of PR-10 in plant defense against biotic stresses; however, little is known about the mechanisms of action of these proteins. This is the first systematic review conducted to gather information on the subject and to reveal the possible mechanisms of action that PR-10 perform.

Methods

Therefore, three databases were used for the article search: PubMed, Web of Science, and Scopus. To avoid bias, a protocol with inclusion and exclusion criteria was prepared. In total, 216 articles related to the proposed objective of this study were selected.

Results

The participation of PR-10 was revealed in the plant's defense against several stressor agents such as viruses, bacteria, fungi, oomycetes, nematodes and insects, and studies involving fungi and bacteria were predominant in the selected articles. Studies with combined techniques showed a compilation of relevant information about PR-10 in biotic stress that collaborate with the understanding of the mechanisms of action of these molecules. The up-regulation of PR-10 was predominant under different conditions of biotic stress, in addition to being more expressive in resistant varieties both at the transcriptional and translational level.

Discussion

Biological models that have been proposed reveal an intrinsic network of molecular interactions involving the modes of action of PR-10. These include hormonal pathways, transcription factors, physical interactions with effector proteins or pattern recognition receptors and other molecules involved with the plant's defense system.

Conclusion

The molecular networks involving PR-10 reveal how the plant's defense response is mediated, either to trigger susceptibility or, based on data systematized in this review, more frequently, to have plant resistance to the disease.

Identification of the Function of the Pathogenesis-Related Protein GmPR1L in the Resistance of Soybean to Cercospora sojina Hara

Pathogenesis-related proteins, often used as molecular markers of disease resistance in plants, can enable plants to obtain systemic resistance. In this study, a gene encoding a pathogenesis-related protein was identified via RNA-seq sequencing analysis performed at different stages of soybean seedling development. Because the gene sequence showed the highest similarity with PR1L sequence in soybean, the gene was named GmPR1-9-like (GmPR1L). GmPR1L was either overexpressed or silenced in soybean seedlings through Agrobacterium-mediated transformation to examine the resistance of soybean to infection caused by Cercospora sojina Hara. The results revealed that GmPR1L-overexpressing soybean plants had a smaller lesion area and improved resistance to C. sojina infection, whereas GmPR1L-silenced plants had low resistance to C. sojina infection. Fluorescent real-time PCR indicated that overexpression of GmPR1L induced the expression of genes such as WRKY, PR9, and PR14, which are more likely to be co-expressed during C. sojina infection. Furthermore, the activities of SOD, POD, CAT, and PAL were significantly increased in GmPR1L-overexpressing soybean plants after seven days of infection. The resistance of the GmPR1L-overexpressing lines OEA1 and OEA2 to C. sojina infection was significantly increased from a neutral level in wild-type plants to a moderate level. These findings predominantly reveal the positive role of GmPR1L in inducing resistance to C. sojina infection in soybean, which may facilitate the production of improved disease-resistant soybean cultivars in the future.

A novel rubber tree PR-10 protein involved in host-defense response against the white root rot fungus Rigidoporus microporus

BACKGROUND

White root rot disease in rubber trees, caused by the pathogenic fungi Rigidoporus microporus, is currently considered a major problem in rubber tree plantations worldwide. Only a few reports have mentioned the response of rubber trees occurring at the non-infection sites, which is crucial for the disease understanding and protecting the yield losses.

RESULTS

Through a comparative proteomic study using the two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) technique, the present study reveals some distal-responsive proteins in rubber tree leaves during the plant-fungal pathogen interaction. From a total of 12 selected differentially expressed protein spots, several defense-related proteins such as molecular chaperones and ROS-detoxifying enzymes were identified. The expression of 6 candidate proteins was investigated at the transcript level by Reverse Transcription Quantitative PCR (RT-qPCR). In silico, a highly-expressed uncharacterized protein LOC110648447 found in rubber trees was predicted to be a protein in the pathogenesis-related protein 10 (PR-10) class. In silico promoter analysis and structural-related characterization of this novel PR-10 protein suggest that it plays a potential role in defending rubber trees against R. microporus infection. The promoter contains WRKY-, MYB-, and other defense-related cis-acting elements. The structural model of the novel PR-10 protein predicted by I-TASSER showed a topology of the Bet v 1 protein family, including a conserved active site and a ligand-binding hydrophobic cavity.

CONCLUSIONS

A novel protein in the PR-10 group increased sharply in rubber tree leaves during interaction with the white root rot pathogen, potentially contributing to host defense. The results of this study provide information useful for white root rot disease management of rubber trees in the future.

Isolation and characterization of a pathogenesis-related protein 1 (SlPR1) gene with induced expression in tomato (Solanum lycopersicum) during Ralstonia solanacearum infection

In order to explore the function of pathogenesis-related (PR) proteins in regulating tomato (Solanum lycopersicum) biological stress response, a PR protein gene (SlPR1) (Gen ID: Solyc01g106620.2) was isolated from tomato by RT-PCR. The full-length cDNA was 760 bp, which encoded a total of 179 amino acids. The cDNA contained a 42 bp 5' non-coding region, a 178 bp 3' non-coding region, and an open reading frame (ORF) of 540 bp. Homologous sequence alignment and phylogenetic analysis indicated that SlPR1 was highly homologous with a S. tuberosum PR1 protein, followed by S. pennellii. The predicted molecular weight of SlPR1 was 20,123.47 Da, the isoelectric point was 8.48, and the protein was found to be a secreted protein with a transmembrane structure. Quantitative real-time PCR (qRT-PCR) revealed that SlPR1 gene expression was highest in tomato stems, and could be induced by infection with Ralstonia solanacearum, and treatment with salicylic acid (SA) and methyl jasmonate acid (MeJA).Virus-induced gene silencing (VIGS) of SlPR1 decreased plant resistance to bacterial wilt, suggesting that SlPR1 positively regulates tomato resistance to this disease.This study provides a reference for the further exploration of the role of SlPR1 in the response of tomato to bacterial wilt and other stressors.

Identification and expression analysis of maize NF-YA subunit genes

NF-YAs encode subunits of the nuclear factor-Y (NF-Y) gene family. NF-YAs represent a kind of conservative transcription factor in plants and are involved in plant growth and development, as well as resistance to biotic and abiotic stress. In this study, 16 maize (Zea mays) NF-YA subunit genes were identified using bioinformatics methods, and they were divided into three categories by a phylogenetic analysis. A conserved domain analysis showed that most contained a CCAAT-binding transcription factor (CBFB) _NF-YA domain. Maize NF-YA subunit genes showed very obvious tissue expression characteristics. The expression level of the NF-YA subunit genes significantly changed under different abiotic stresses, including Fusarium graminearum infection and salicylic acid (SA) or jasmonic acid (JA) treatments. After inoculation with Setosphaeria turcica and Cochliobolus heterostrophus, the lesion areas of nfya01 and nfya06 were significantly larger than that of B73, indicating that ZmNFYA01 and ZmNFYA06 positively regulated maize disease resistance. ZmNFYA01 and ZmNFYA06 may regulated maize disease resistance by affecting the transcription levels of ZmPRs. Thus, NF-YA subunit genes played important roles in promoting maize growth and development and resistance to stress. The results laid a foundation for clarifying the functions and regulatory mechanisms of NF-YA subunit genes in maize.

Meta-analysis and co-expression analysis revealed stable QTL and candidate genes conferring resistances to Fusarium and Gibberella ear rots while reducing mycotoxin contamination in maize

Fusarium (FER) and Gibberella ear rots (GER) are the two most devastating diseases of maize (Zea mays L.) which reduce yield and affect grain quality worldwide, especially by contamination with mycotoxins. Genetic improvement of host resistance to effectively tackle FER and GER diseases requires the identification of stable quantitative trait loci (QTL) to facilitate the application of genomics-assisted breeding for improving selection efficiency in breeding programs. We applied improved meta-analysis algorithms to re-analyze 224 QTL identified in 15 studies based on dense genome-wide single nucleotide polymorphisms (SNP) in order to identify meta-QTL (MQTL) and colocalized genomic loci for fumonisin (FUM) and deoxynivalenol (DON) accumulation, silk (SR) and kernel (KR) resistances of both FER and GER, kernel dry-down rate (KDD) and husk coverage (HC). A high-resolution genetic consensus map with 36,243 loci was constructed and enabled the projection of 164 of the 224 collected QTL. Candidate genes (CG) mining was performed within the most refined MQTL, and identified CG were cross-validated using publicly available transcriptomic data of maize under Fusarium graminearum infection. The meta-analysis revealed 40 MQTL, of which 29 were associated each with 2-5 FER- and/or GER-related traits. Twenty-eight of the 40 MQTL were common to both FER and GER resistances and 19 MQTL were common to silk and kernel resistances. Fourteen most refined MQTL on chromosomes 1, 2, 3, 4, 7 and 9 harbored a total of 2,272 CG. Cross-validation identified 59 of these CG as responsive to FER and/or GER diseases. MQTL ZmMQTL2.2, ZmMQTL9.2 and ZmMQTL9.4 harbored promising resistance genes, of which GRMZM2G011151 and GRMZM2G093092 were specific to the resistant line for both diseases and encoded "terpene synthase21 (tps21)" and "flavonoid O-methyltransferase2 (fomt2)", respectively. Our findings revealed stable refined MQTL harboring promising candidate genes for use in breeding programs for improving FER and GER resistances with reduced mycotoxin accumulation. These candidate genes can be transferred into elite cultivars by integrating refined MQTL into genomics-assisted backcross breeding strategies.

Assessment of root-specific promoters in banana and tobacco and identification of a banana TIP2 promoter with strong root activity

Genetic modification is one possible strategy to generate bananas (Musa spp.) with resistance to the soil-borne pathogen causing Fusarium wilt. The availability of banana root-specific promoters to target transgene expression to the sites of infection would be beneficial. We have assessed 18 promoter sequences derived from a range of plant species for their expression profiles in banana tissues to identify those with root-specific activity. Promoter sequences were isolated and fused to the β-glucuronidase (GUS) gene to assess their expression levels and tissue specificity in both banana and the model plant tobacco. Two heterologous promoters conferring high root expression levels in banana were identified, including a β-glucosidase 1 (GLU1) promoter from maize and the RB7-type tonoplast intrinsic protein (TIP)-2 promoter from strawberry. Further, a novel Musa TIP2-2 promoter sequence was isolated and characterized which, when fused to the GUS gene, conferred very high GUS expression levels in banana roots. These promoters will expand the options for the control of gene expression in genetically modified bananas, providing a tool to develop plants with resistance not only to soil-borne diseases such as Fusarium wilt, but also for the improvement of other traits, such as nematode resistance, nutrition or abiotic stress resistance.

Gene Co-expression Network Analysis of the Comparative Transcriptome Identifies Hub Genes Associated With Resistance to Aspergillus flavus L. in Cultivated Peanut (Arachis hypogaea L.)

Cultivated peanut (Arachis hypogaea L.), a cosmopolitan oil crop, is susceptible to a variety of pathogens, especially Aspergillus flavus L., which not only vastly reduce the quality of peanut products but also seriously threaten food safety for the contamination of aflatoxin. However, the key genes related to resistance to Aspergillus flavus L. in peanuts remain unclear. This study identifies hub genes positively associated with resistance to A. flavus in two genotypes by comparative transcriptome and weighted gene co-expression network analysis (WGCNA) method. Compared with susceptible genotype (Zhonghua 12, S), the rapid response to A. flavus and quick preparation for the translation of resistance-related genes in the resistant genotype (J-11, R) may be the drivers of its high resistance. WGCNA analysis revealed that 18 genes encoding pathogenesis-related proteins (PR10), 1-aminocyclopropane-1-carboxylate oxidase (ACO1), MAPK kinase, serine/threonine kinase (STK), pattern recognition receptors (PRRs), cytochrome P450, SNARE protein SYP121, pectinesterase, phosphatidylinositol transfer protein, and pentatricopeptide repeat (PPR) protein play major and active roles in peanut resistance to A. flavus. Collectively, this study provides new insight into resistance to A. flavus by employing WGCNA, and the identification of hub resistance-responsive genes may contribute to the development of resistant cultivars by molecular-assisted breeding.

Comparative transcriptome profiling and co-expression network analysis uncover the key genes associated withearly-stage resistance to Aspergillus flavus in maize

BACKGROUND

The fungus Aspergillus flavus (A. flavus) is a serious threat to maize (Zea mays) production worldwide. It causes considerable yield and economic losses, and poses a health risk to humans and livestock due to the high toxicity of aflatoxin. However, key genes and regulatory networks conferring maize resistance to A. flavus are not clear, especially at the early stage of infection. Here, we performed a comprehensive transcriptome analysis of two maize inbred lines with contrasting resistance to A. flavus infection.

RESULTS

The pairwise comparisons between mock and infected kernels in each line during the first 6 h post inoculation (hpi) showed that maize resistance to A. flavus infection was specific to the genotype and infection stage, and defense pathways were strengthened in the resistant line. Further comparison of the two maize lines revealed that the infection-induced up-regulated differentially expressed genes (DEGs) in the resistant line might underlie the enhanced resistance. Gene co-expression network analysis by WGCNA (weighted gene co-expression network analysis) identified 7 modules that were significantly associated with different infection stages, and 110 hub genes of these modules. These key regulators mainly participate in the biosynthesis of fatty acid and antibiotics. In addition, 90 candidate genes for maize resistance to A. flavus infection and/or aflatoxin contamination obtained in previous studies were confirmed to be differentially expressed between the resistant and susceptible lines within the first 6 hpi.

CONCLUSION

This work unveiled more A. flavus resistance genes and provided a detailed regulatory network of early-stage resistance to A. flavus in maize.

Review: Biological functions of major latex-like proteins in plants

Major latex-like proteins (MLPs) have been identified in dicots and monocots. They are members of the birch pollen allergen Bet v 1 family as well as pathogenesis-related proteins class 10. MLPs have two main features. One is binding affinity toward various hydrophobic compounds, such as long-chain fatty acids, steroids, and systemic acquired resistance signals, via its internal hydrophobic cavity or hydrophobic residues on its surface. MLPs transport such compounds to other organs via phloem and xylem vessels and contribute to the expression of physiologically important ligands' activity in the particular organs. The second feature is responses to abiotic and biotic stresses. MLPs are involved in drought and salt tolerance through the mediation of plant hormone signaling pathways. MLPs generate resistance against pathogens by the induction of pathogenesis-related protein genes. Therefore, MLPs play crucial roles in drought and salt tolerance and resistance against pathogens. However, knowledge of MLPs is fragmented, and an overview of them is needed. Herein, we summarize the current knowledge of the biological functions of MLPs, which to our knowledge, is the first review about MLPs that has been reported.

In-vitro anti-fungal assay and association analysis reveal a role for the Pinus monticola PR10 gene (PmPR10-3.1) in quantitative disease resistance to white pine blister rust

Pathogenesis-related (PR) proteins play important roles in plant defense response. However, functional investigation of PR10 genes is still limited and their physiological roles have not been conclusively characterized in biological processes of conifer trees. Here, we identified multiple novel members in the western white pine (Pinus monticola) PmPR10 family by bioinformatic mining available transcriptomic data. Phylogenetic analysis of protein sequences revealed four PR10 and two PR10-like clusters with a high synteny across different species of five-needle pines. Of 10 PmPR10 genes, PmPR10-3.1 was selected and expressed in Escherichia coli. The purified recombinant protein exhibited inhibitory effects on spore hyphal growth of fungal pathogens Cronartium ribicola, Phoma exigua, and Phoma argillacea by in-vitro anti-fungal analysis. Genetic variation analysis detected a total of 21 single nucleotide polymorphisms (SNPs) within PmPR10-3.1 in a collection of P. monticola seed families. A nonsynonymous SNP (t178g) showed significant association with relative levels of quantitative disease resistance (QDR), explaining about 8.7% of phenotypic variation as the peak value across all SNPs. Our results provide valuable insight into the genetic architecture underlying P. monticola QDR and imply that PmPR10-3.1 may function as an important component in conifer basal immunity for non-specific resistance to a wide spectrum of pathogens.

Enhanced Abiotic Stress Tolerance of Vicia faba L. Plants Heterologously Expressing the PR10a Gene from Potato

Pathogenesis-related (PR) proteins are known to play relevant roles in plant defense against biotic and abiotic stresses. In the present study, we characterize the response of transgenic faba bean (Vicia faba L.) plants encoding a PR10a gene from potato (Solanum tuberosum L.) to salinity and drought. The transgene was under the mannopine synthetase (pMAS) promoter. PR10a-overexpressing faba bean plants showed better growth than the wild-type plants after 14 days of drought stress and 30 days of salt stress under hydroponic growth conditions. After removing the stress, the PR10a-plants returned to a normal state, while the wild-type plants could not be restored. Most importantly, there was no phenotypic difference between transgenic and non-transgenic faba bean plants under well-watered conditions. Evaluation of physiological parameters during salt stress showed lower Na⁺-content in the leaves of the transgenic plants, which would reduce the toxic effect. In addition, PR10a-plants were able to maintain vegetative growth and experienced fewer photosystem changes under both stresses and a lower level of osmotic stress injury under salt stress compared to wild-type plants. Taken together, our findings suggest that the PR10a gene from potato plays an important role in abiotic stress tolerance, probably by activation of stress-related physiological processes.

A Valsa mali Effector Protein 1 Targets Apple (Malus domestica) Pathogenesis-Related 10 Protein to Promote Virulence

To successfully colonize the plants, the pathogenic microbes secrete a mass of effector proteins which manipulate host immunity. Apple valsa canker is a destructive disease caused by the weakly parasitic fungus Valsa mali. A previous study indicated that the V. mali effector protein 1 (VmEP1) is an essential virulence factor. However, the pathogenic mechanism of VmEP1 in V. mali remains poorly understood. In this study, we found that the apple (Malus domestica) pathogenesis-related 10 proteins (MdPR10) are the virulence target of VmEP1 using a yeast two-hybrid screening. By bimolecular fluorescence (BiFC) and coimmunoprecipitation (Co-IP), we confirmed that the VmEP1 interacts with MdPR10 in vivo. Silencing of MdPR10 notably enhanced the V. mali infection, and overexpression of MdPR10 markedly reduced its infection, which corroborates its positive role in plant immunity against V. mali. Furthermore, we showed that the co-expression of VmEP1 with MdPR10 compromised the MdPR10-mediated resistance to V. mali. Taken together, our results revealed a mechanism by which a V. mali effector protein suppresses the host immune responses by interfering with the MdPR10-mediated resistance to V. mali during the infection.

Differential regulation of the durum wheat Pathogenesis-related protein (PR1) by Calmodulin TdCaM1.3 protein

In plants, pathogenesis-related 1 protein (PR1) is considered as important defense protein. The production and accumulation of PR proteins in plants are one of the important responses to several biotic and abiotic stresses. In this regard, PR1 gene was isolated from Triticum turgidum ssp durum and was named as TdPR1.2. The amino acid sequence of TdPR1.2 protein showed 100%, 97.13%, and 44.41% with known PR1 proteins isolated from Triticum aestivum TdPR1-18, PRB1.2 of Aegilops tauschii subsp. tauschii and Arabidopsis thaliana respectively. qRT-PCR showed that TdPR1.2 was induced specially in leaves of durum wheat treated with Salicylic acid for 48 h. Besides, bioinformatic analysis showed that the durum wheat TdPR1.2 harbors a calmodulin binding domain located in it's C-terminal part and that this domain is conserved among different PR1 proteins isolated so far. However, no information is available about the regulation of PR genes by calmodulin and Ca²⁺ complex (CaM/Ca²⁺). Here, we showed that TdPR1.2 gene exhibits an antibacterial effect as revealed by the in vitro tests against 8 different bacteria and against the fungi Septoria tritici. In addition, we demonstrate for the first time that PR1 proteins are able to bind to CaM in a Ca²⁺-dependent manner via a GST-Pull down assay. Finally, in presence of Mn²⁺ cations, CaM/Ca²⁺ complex stimulated the antimicrobial effect of TdPR1.2. Such effects were not reported so far, and raise a possible role for CaM/Ca²⁺ complex in the regulation of plant PRs during cellular response to external signals.

Physico-chemical characterization and topological analysis of pathogenesis-related proteins from Arabidopsis thaliana and Oryza sativa using in-silico approaches

Plants are constantly under the threat of various biotic and abiotic stress conditions and to overcome these stresses, they have evolved multiple mechanisms including systematic accumulation of different phytohormones, phytoalexins and pathogenesis related (PR) proteins. PR proteins are cluster of proteins with low molecular weight which get incited in plants under different stresses. In this paper, in-silico approaches are used to compare the physico-chemical properties of 6 PR proteins (PR1, PR2, PR5, PR9, PR10, PR12) of Arabidopsis thaliana and Oryza sativa. Topological analysis revealed the presence of transmembrane localization of PR2 and absence of transmembrane domain in PR10 of both model plants studied. Amino acid composition shows the dominance of small aliphatic amino acids i.e. alanine, glycine and serine in both plants studied. These results highlights the similarities and differences between PRs of both model plants, which provides clue towards their diversified roles in plants.

Functional Biology and Molecular Mechanisms of Host-Pathogen Interactions for Aflatoxin Contamination in Groundnut (Arachis hypogaea L.) and Maize (Zea mays L.)

Aflatoxins are secondary metabolites produced by soilborne saprophytic fungus Aspergillus flavus and closely related species that infect several agricultural commodities including groundnut and maize. The consumption of contaminated commodities adversely affects the health of humans and livestock. Aflatoxin contamination also causes significant economic and financial losses to producers. Research efforts and significant progress have been made in the past three decades to understand the genetic behavior, molecular mechanisms, as well as the detailed biology of host-pathogen interactions. A range of omics approaches have facilitated better understanding of the resistance mechanisms and identified pathways involved during host-pathogen interactions. Most of such studies were however undertaken in groundnut and maize. Current efforts are geared toward harnessing knowledge on host-pathogen interactions and crop resistant factors that control aflatoxin contamination. This study provides a summary of the recent progress made in enhancing the understanding of the functional biology and molecular mechanisms associated with host-pathogen interactions during aflatoxin contamination in groundnut and maize.

A Pathogenesis-Related Protein-Like Gene Is Involved in the Panax notoginseng Defense Response to the Root Rot Pathogen

Pathogenesis-related proteins (PRs) are a class of proteins that accumulate in response to biotic and abiotic stresses to protect plants from damage. In this study, a gene encoding a PR-like protein (PnPR-like) was isolated from Panax notoginseng, which is used in traditional Chinese herbal medicines. An analysis of gene expression in P. notoginseng indicated that PnPR-like was responsive to an infection by the root rot pathogen Fusarium solani. The expression of this gene was induced by several signaling molecules, including methyl jasmonate, ethephon, hydrogen peroxide, and salicylic acid. The PnPR-like-GFP fusion gene was transiently expressed in onion (Allium cepa) epidermal cells, which revealed that PnPR-like is a cytoplasmic protein. The purified recombinant PnPR-like protein expressed in Escherichia coli had antifungal effects on F. solani and Colletotrichum gloeosporioides as well as inhibited the spore germination of F. solani. Additionally, the in vitro ribonuclease (RNase) activity of the recombinant PnPR-like protein was revealed. The PnPR-like gene was inserted into tobacco (Nicotiana tabacum) to verify its function. The gene was stably expressed in T₂ transgenic tobacco plants, which exhibited more RNase activity and greater disease resistance than the wild-type tobacco. Moreover, the transient expression of hairpin RNA targeting PnPR-like in P. notoginseng leaves increased the susceptibility to F. solani and decreased the PnPR-like expression level. In conclusion, the cytoplasmic protein PnPR-like, which has RNase activity, is involved in the P. notoginseng defense response to F. solani.

Transgenic expression of Hyp-1 gene from Hypericum perforatum L. alters expression of defense-related genes and modulates recalcitrance to Agrobacterium tumefaciens

MAIN CONCLUSION

Phenolic oxidative coupling protein (Hyp-1) isolated from Hypericum perforatum L. was characterized as a defense gene involved in H. perforatum recalcitrance to Agrobacterium tumefaciens-mediated transformation Hypericum perforatum L. is a reservoir of high-value secondary metabolites of increasing interest to researchers and to the pharmaceutical industry. However, improving their production via genetic manipulation is a challenging task, as H. perforatum is recalcitrant to Agrobacterium tumefaciens-mediated transformation. Here, phenolic oxidative coupling protein (Hyp-1), a pathogenesis-related (PR) class 10 family gene, was selected from a subtractive cDNA library from A. tumefaciens-treated H. perforatum suspension cells. The role of Hyp-1 in defense against A. tumefaciens was analyzed in transgenic Nicotiana tabacum and Lactuca sativa overexpressing Hyp-1, and in Catharanthus roseus silenced for its homologous Hyp-1 gene, CrIPR. Results showed that Agrobacterium-mediated expression efficiency greatly decreased in Hyp-1 transgenic plants. However, silencing of CrIPR induced CrPR-5 expression and decreased expression efficiency of Agrobacterium. The expression of core genes involved in several defense pathways was also analyzed in Hyp-1 transgenic tobacco plants. Overexpression of Hyp-1 led to an ample down-regulation of key genes involved in auxin signaling, microRNA-based gene silencing, detoxification of reactive oxygen species, phenylpropanoid pathway and PRs. Moreover, Hyp-1 was detected in the nucleus, plasma membrane and the cytoplasm of epidermal cells by confocal microscopy. Overall, our findings suggest Hyp-1 modulates recalcitrance to A. tumefaciens-mediated transformation in H. perforatum.

Role of primary metabolites in plant defense against pathogens

Plants under natural environment facing various pathogens, tend to produce defense to maintain their fitness and minimize pathogenic damage. Plant-pathogens interaction is gaining more importance by researches as, their means of the fight are primary metabolites. The ultimate result of either means of defense is pathogenesis or resistance. Plant defense mechanisms can be grouped either into inducible and constitutive defense or chemical, structural and morphological defense. Majority of defense mechanisms have a passive role, i.e. only defensive against pathogens, but a few are very active. Plant primary metabolites are catching interest in their immunity role. Deep information of molecular mechanisms involved during the plant-pathogen system is need of the day for future disease control. This review will highlight the role of primary metabolites and their mechanism of action in plant defense.

Glycine rich proline rich protein from Sorghum bicolor serves as an antimicrobial protein implicated in plant defense response

KEY MESSAGE

Sorghum glycine rich proline rich protein (SbGPRP1) exhibit antimicrobial properties and play a crucial role during biotic stress condition. Several proteins in plants build up the innate immune response system in plants which get triggered during the occurrence of biotic stress. Here we report the functional characterization of a glycine-rich proline-rich protein (SbGPRP1) from Sorghum which was previously demonstrated to be involved in abiotic stresses. Expression studies carried out with SbGPRP1 showed induced expression upon application of phytohormones like salicylic acid which might be the key in fine-tuning the expression level. Upon challenging the Sorghum plants with a compatible pathogen the SbGprp1 transcript was found to be upregulated. SbGPRP1 encodes a 197 amino acid polypeptide which was bacterially-expressed and purified for in vitro assays. Gram-positive bacteria like Bacillus and phytopathogen Rhodococcus fascians showed inhibited growth in the presence of the protein. The NPN assay, electrolytic leakage and SEM analysis showed membrane damage in bacterial cells. Ectopic expression of SbGPRP1 in tobacco plants led to enhanced tolerance towards infection caused by R. fascians. Though the N-terminal part of the protein showed disorderness the C-terminal end was quite capable of forming several α-helices which was correlated with CD spectroscopic analysis. Here, we have tried to determine the structural model for the protein and predicted the association of antimicrobial activity with the C-terminal region of the protein.

Bacillomycin D inhibits growth of Rhizopus stolonifer and induces defense-related mechanism in cherry tomato

The inhibitory effect of Bacillomycin D, a cyclic lipopeptide, on Rhizopus stolonifer colonization of cherry tomato was studied, and its possible mechanism of action was explored. Bacillomycin D showed a direct inhibitory effect on R. stolonifer spore germination and mycelial growth in vitro. It conferred both a direct inhibitory effect on R. stolonifer growth in cherry tomato in vivo and induced host resistance in cherry tomato. Moreover, Bacillomycin D treatment significantly increased the activities of plant defense-related enzymes, including chitinase (CHI), β-1,3-glucanase (GLU), phenylalanine ammonia-lyase (PAL), and peroxidase (POD). Real-time PCR (RT-PCR) showed that defense-related genes involved in the salicylic acid defense signaling pathway and genes encoding pathogenesis-related proteins were up-regulated in Bacillomycin D treatment. Furthermore, Bacillomycin D-C16 resulted in direct inhibition and a remarkable induced resistance to R. stolonifer which was higher than as induced by Bacillomycin D-C14. Together, the data indicated that Bacillomycin D can control the growth of R. stolonifer through both the direct inhibition of the fungus and the activation of defense-related genes and enzymes in cherry tomato.

Phosphorylation-dependent ribonuclease activity of Fra a 1 proteins

Abiotic and biotic stress situations cause the upregulation of the transcription of a number of plant defence genes. They code for so-called pathogenesis-related (PR) proteins such as PR proteins of class-10 (PR-10), whose biological functions are still unclear. PR10 proteins are members of the Bet v 1 (major birch pollen allergen) superfamily including related proteins from the cultivated strawberry Fragaria × ananassa (Fra a 1 proteins). Here, we analyzed the expression of 21 Fra a 1 genes in different tissues of the strawberry plant by quantitative real-time PCR. Thirteen members were mainly expressed in roots, three in stems, two in red fruits and leaves, and one in flowers. Five genes (Fra a 1.04-1.08) were selected based on their expression profiles, heterologously expressed in Escherichia coli, and their recombinant proteins functionally characterized. Ribonuclease activity, demonstrated by in-solution and in-gel RNA degradation assays, indicated complete hydrolysis of RNA only by Fra a 1.06. Moreover, phosphorylation assays showed that except for Fra a 1.06, the remaining four recombinant proteins were phosphorylated. Consequently, we investigated whether the phosphorylation status of the proteins affects their ribonuclease activity. Using an in-solution as well as an in-gel RNase activity assay, results demonstrated that the four recombinant proteins, dephosphorylated with phosphatases, exhibited ribonucleolytic activity against total RNA. Thus, the PR10 related proteins characterized in this study harbour a phosphorylation-dependent RNase activity. The results shed new light on the assumed function of PR10 proteins in plant defence.

Purification and characterization of two pathogenesis-related class 10 protein isoforms with ribonuclease activity from the fresh Angelica sinensis roots

In this study, two pathogenesis-related (PR) class 10 protein isoforms, ASPR-1 and ASPR-2, were purified from fresh roots of the Chinese medicinal plant Angelica sinensis (A. sinensis) using 80% ammonium sulfate precipitation, Sephadex G50 gel filtration chromatography, and DEAE-Sepharose ion-exchange chromatography. The molecular masses of ASPR-1 and ASPR-2 were estimated to be 16.66 kDa and 16.46 kDa, respectively, using sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The isoforms are both glycoproteins containing glycosyl contents of 1.8% (ASPR-1) and 3.4% (ASPR-2). The two isoforms were predominantly present as monomers, but they partially dimerized in solution. The 15 N-terminal amino acids of ASPR-1 were determined to be GIQKTEVEAPSTVSA, with significant sequence homology to certain PR-10 proteins. ASPR-2 was also identified using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS) analysis to be a PR-10 protein. The isoforms both exhibited ribonuclease (RNase) activity, with ASPR-2 having higher specific activity (128.85 U mg^-1) than ASPR-1 (68.67 U mg^-1). The isoforms had the same optimal temperature of 50 °C but different optimal pH values of 5.0 (ASPR-1) and 6.0 (ASPR-2). The RNase activities of the isoforms were both stable for 30 min at 50 °C, rapidly decreasing at higher or lower processing temperatures. However, ASPR-1 retained higher residual activity (89.4%-80.9%) than ASPR-2 (74.3%-67.9%) at temperatures from 40 °C to 60 °C. These results provide additional information to enrich the current knowledge of poorly annotated A. sinensis proteins.

Pathogenesis-related proteins and peptides as promising tools for engineering plants with multiple stress tolerance

Pathogenesis-related (PR) proteins and antimicrobial peptides (AMPs) are a group of diverse molecules that are induced by phytopathogens as well as defense related signaling molecules. They are the key components of plant innate immune system especially systemic acquired resistance (SAR), and are widely used as diagnostic molecular markers of defense signaling pathways. Although, PR proteins and peptides have been isolated much before but their biological function remains largely enigmatic despite the availability of new scientific tools. The earlier studies have demonstrated that PR genes provide enhanced resistance against both biotic and abiotic stresses, which make them one of the most promising candidates for developing multiple stress tolerant crop varieties. In this regard, plant genetic engineering technology is widely accepted as one of the most fascinating approach to develop the disease resistant transgenic crops using different antimicrobial genes like PR genes. Overexpression of PR genes (chitinase, glucanase, thaumatin, defensin and thionin) individually or in combination have greatly uplifted the level of defense response in plants against a wide range of pathogens. However, the detailed knowledge of signaling pathways that regulates the expression of these versatile proteins is critical for improving crop plants to multiple stresses, which is the future theme of plant stress biology. Hence, this review provides an overall overview on the PR proteins like their classification, role in multiple stresses (biotic and abiotic) as well as in various plant defense signaling cascades. We also highlight the success and snags of transgenic plants expressing PR proteins and peptides.

PR-10 proteins as potential mediators of melatonin-cytokinin cross-talk in plants: crystallographic studies of LlPR-10.2B isoform from yellow lupine

LlPR-10.2B, a Pathogenesis-related class 10 (PR-10) protein from yellow lupine (Lupinus luteus) was crystallized in complex with melatonin, an emerging important plant regulator and antioxidant. The structure reveals two molecules of melatonin bound in the internal cavity of the protein, plus a very well-defined electron density near the cavity entrance, corresponding to an unknown ligand molecule comprised of two flat rings, which is most likely a product of melatonin transformation. In a separate LlPR-10.2B co-crystallization experiment with an equimolar mixture of melatonin and trans-zeatin, which is a cytokinin phytohormone well recognized as a PR-10-binding partner, a quaternary 1 : 1 : 1 : 1 complex was formed, in which one of the melatonin-binding sites has been substituted with trans-zeatin, whereas the binding of melatonin at the second binding site and binding of the unknown ligand are undisturbed. This unusual complex, when compared with the previously described PR-10/trans-zeatin complexes and with the emerging structural information about melatonin binding by PR-10 proteins, provides intriguing insights into the role of PR-10 proteins in phytohormone regulation in plants, especially with the involvement of melatonin, and implicates the PR-10 proteins as low-affinity melatonin binders under the conditions of elevated melatonin concentration.

DATABASES

Atomic coordinates and processed structure factors corresponding to the final models of the LlPR-10.2B/melatonin and LlPR-10.2B/melatonin + trans-zeatin complexes have been deposited with the Protein Data Bank (PDB) under the accession codes 5MXB and 5MXW. The corresponding raw X-ray diffraction images have been deposited in the RepOD Repository at the Interdisciplinary Centre for Mathematical and Computational Modelling (ICM) of the University of Warsaw, Poland, and are available for download with the following Digital Object Identifiers (DOI): https://doi.org/10.18150/repod.9923638 and https://doi.org/10.18150/repod.6621013.

Transcriptome profiling of two maize inbreds with distinct responses to Gibberella ear rot disease to identify candidate resistance genes

Background

Gibberella ear rot (GER) is one of the most economically important fungal diseases of maize in the temperate zone due to moldy grain contaminated with health threatening mycotoxins. To develop resistant genotypes and control the disease, understanding the host-pathogen interaction is essential.

Results

RNA-Seq-derived transcriptome profiles of fungal- and mock-inoculated developing kernel tissues of two maize inbred lines were used to identify differentially expressed transcripts and propose candidate genes mapping within GER resistance quantitative trait loci (QTL). A total of 1255 transcripts were significantly (P ≤ 0.05) up regulated due to fungal infection in both susceptible and resistant inbreds. A greater number of transcripts were up regulated in the former (1174) than the latter (497) and increased as the infection progressed from 1 to 2 days after inoculation. Focusing on differentially expressed genes located within QTL regions for GER resistance, we identified 81 genes involved in membrane transport, hormone regulation, cell wall modification, cell detoxification, and biosynthesis of pathogenesis related proteins and phytoalexins as candidate genes contributing to resistance. Applying droplet digital PCR, we validated the expression profiles of a subset of these candidate genes from QTL regions contributed by the resistant inbred on chromosomes 1, 2 and 9.

Conclusion

By screening global gene expression profiles for differentially expressed genes mapping within resistance QTL regions, we have identified candidate genes for gibberella ear rot resistance on several maize chromosomes which could potentially lead to a better understanding of Fusarium resistance mechanisms.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4513-4) contains supplementary material, which is available to authorized users.

Improvement of Verticillium Wilt Resistance by Applying Arbuscular Mycorrhizal Fungi to a Cotton Variety with High Symbiotic Efficiency under Field Conditions

Arbuscular mycorrhizal fungi (AMF) play an important role in nutrient cycling processes and plant stress resistance. To evaluate the effect of Rhizophagus irregularis CD1 on plant growth promotion (PGP) and Verticillium wilt disease, the symbiotic efficiency of AMF (SEA) was first investigated over a range of 3% to 94% in 17 cotton varieties. The high-SEA subgroup had significant PGP effects in a greenhouse. From these results, the highest-SEA variety of Lumian 1 was selected for a two-year field assay. Consistent with the performance from the greenhouse, the AMF-mediated PGP of Lumian 1 also produced significant results, including an increased plant height, stem diameter, number of petioles, and phosphorus content. Compared with the mock treatment, AMF colonization obviously inhibited the symptom development of Verticillium dahliae and more strongly elevated the expression of pathogenesis-related genes and lignin synthesis-related genes. These results suggest that AMF colonization could lead to the mycorrhiza-induced resistance (MIR) of Lumian 1 to V. dahliae. Interestingly, our results indicated that the AMF endosymbiont could directly inhibit the growth of phytopathogenic fungi including V. dahliae by releasing undefined volatiles. In summary, our results suggest that stronger effects of AMF application result from the high-SEA.

A sugarcane pathogenesis-related protein, ScPR10, plays a positive role in defense responses under Sporisorium scitamineum, SrMV, SA, and MeJA stresses

KEY MESSAGE

A pathogenesis-related gene, ScPR10 , was isolated from sugarcane and its bio-function was characterized, demonstrating that ScPR10 was involved in plant defense responses to Sporisorium scitamineum , SrMV, SA, and MeJA stresses. Plant fungal and viral diseases are the major concerns in sugarcane industry. Many anti-fungal and antivirus components, including pathogenesis-related (PR) proteins, have been identified. The pathogenesis-related protein 10 (PR10) is the dominant group in PR families, involved in the plant defense mechanism. In this study, ScPR10 (GenBank Acc. No. KT887884), a 701-bp-length PR10 gene with a 483 bp-length open reading frame, was isolated from sugarcane. Its transient expression in the leaves of Nicotiana benthamiana indicated that the function role of ScPR10 is likely in the nucleus, and it increased the level of H2O2 accumulation in leaf cells. Moreover, ScPR10 could also enhance the resistance of N. benthamiana leaves to infection by Pseudomonas solanacearum and Fusarium solani var. coeruleum. Quantitative real-time PCR analysis revealed that ScPR10 was not constitutively expressed in sugarcane tissues due to its high expression in the buds and scant presence in root tips. In addition, the transcript of ScPR10 could be induced by a pathogenic fungus (Sporisorium scitamineum) and a virus (Sorghum mosaic virus, SrMV) in the resistant sugarcane cultivars, while it was down-regulated in the susceptible ones. After exposure to salicylic acid (SA) and methyl jasmonate (MeJA), ScPR10 peaked at 6 and 12 h, respectively. These results suggest that ScPR10 can play a positive role in sugarcane defense responses to S. scitamineum, SrMV, SA, and MeJA stresses.

Functional roles of the pepper leucine-rich repeat protein and its interactions with pathogenesis-related and hypersensitive-induced proteins in plant cell death and immunity

Pepper leucine-rich repeat protein (CaLRR1) interacts with defense response proteins to regulate plant cell death and immunity. This review highlights the current understanding of the molecular functions of CaLRR1 and its interactor proteins. Plant cell death and immune responses to microbial pathogens are controlled by complex and tightly regulated molecular signaling networks. Xanthomonas campestris pv. vesicatoria (Xcv)-inducible pepper (Capsicum annuum) leucine-rich repeat protein 1 (CaLRR1) serves as a molecular marker for plant cell death and immunity signaling. In this review, we discuss recent advances in elucidating the functional roles of CaLRR1 and its interacting plant proteins, and understanding how they are involved in the cell death and defense responses. CaLRR1 physically interacts with pepper pathogenesis-related proteins (CaPR10 and CaPR4b) and hypersensitive-induced reaction protein (CaHIR1) to regulate plant cell death and defense responses. CaLRR1 is produced in the cytoplasm and trafficked to the extracellular matrix. CaLRR1 binds to CaPR10 in the cytoplasm and CaPR4b and CaHIR1 at the plasma membrane. CaLRR1 synergistically accelerates CaPR10-triggered hypersensitive cell death, but negatively regulates CaPR4b- and CaHIR1-triggered cell death. CaHIR1 interacts with Xcv filamentous hemagglutinin (Fha1) to trigger disease-associated cell death. The subcellular localization and cellular function of these CaLRR1 interactors during plant cell death and defense responses were elucidated by Agrobacterium-mediated transient expression, virus-induced gene silencing, and transgenic overexpression studies. CaPR10, CaPR4b, and CaHIR1 positively regulate defense signaling mediated by salicylic acid and reactive oxygen species, thereby activating hypersensitive cell death and disease resistance. A comprehensive understanding of the molecular functions of CaLRR1 and its interacting protein partners in cell death and defense responses will provide valuable information for the molecular genetics of plant disease resistance, which could be exploited as a sustainable disease management strategy.

Expression Profiling of Strawberry Allergen Fra a during Fruit Ripening Controlled by Exogenous Auxin

Strawberry fruit contain the allergenic Fra a proteins, members of the pathogenesis-related 10 protein family that causes oral allergic syndrome symptoms. Fra a proteins are involved in the flavonoid biosynthesis pathway, which might be important for color development in fruits. Auxin is an important plant hormone in strawberry fruit that controls fruit fleshiness and ripening. In this study, we treated strawberry fruits with exogenous auxin or auxin inhibitors at pre- and post-harvest stages, and analyzed Fra a transcriptional and translational expression levels during fruit development by real-time PCR and immunoblotting. Pre-harvest treatment with 1-naphthaleneacetic acid (NAA) alone did not affect Fra a expression, but applied in conjunction with achene removal NAA promoted fruit pigmentation and Fra a protein accumulation. The response was developmental stage-specific: Fra a 1 was highly expressed in immature fruit, whereas Fra a 2 was expressed in young to ripe fruit. In post-harvest treatments, auxin did not contribute to Fra a induction. Auxin inhibitors delayed fruit ripening; as a result, they seemed to influence Fra a 1 expression. Thus, Fra a expression was not directly regulated by auxin, but might be associated with the ripening process and/or external factors in a paralog-specific manner.

Cloning, Overexpression and in vitro Antifungal Activity of Zea Mays PR10 Protein

Background

Plants have various defense mechanisms such as production of antimicrobial peptides, particularly pathogenesis related proteins (PR proteins). PR10 family is an essential member of this group, with antifungal, antibacterial and antiviral activities.

Objective

The goal of this study is to assess the antifungal activity of maize PR10 against some of fungal phytopathogens.

Materials and Methods

Zea mays PR10 gene (TN-05-147) was cloned from genomic DNA and cDNA and overexpressed in Escherichia coli. The existence of a 77- bp intron and two exons in PR10 was confi rmed by comparing the genomic and cDNA sequences. The PR10 cDNA was cloned in pET26b (+) expression vector and transformed into E. coli strain Rosetta DE3 in order to express PR10 recombinant protein. Expression of the recombinant protein was checked by western analysis. Recombinant PR10 appeared as insoluble inclusion bodies and thus solubilized and refolded. PR10 was isolated using Ni- NTA column. The activity of the refolded protein was confi rmed by DNA degradation test. The antifungal activity of PR10 was assessed using radial diff usion, disc diff usion and spore germination. The hemolytic assay was performed to investigate the biosafety of recombinant PR10.

Results

Recombinant maize PR10 exerted broad spectrum antifungal activity against Botrytis cinerea, Sclerotinia sclerotiorum, Fusarium oxysporum, Verticillium dahlia and Alternaria solani. Hemolysis biosafety test indicated that the protein is not poisonous to mammalian cells.

Conclusions

Maize PR10 has the potential to be used as the antifungal agent against diff erent fungal phytopathogens. Therefore, this protein can be used in order to produce antifungal agents and fungi resistance transgenic plants.

Comparative Histological and Transcriptional Analysis of Maize Kernels Infected with Aspergillus flavus and Fusarium verticillioides

Aspergillus flavus and Fusarium verticillioides infect maize kernels and contaminate them with the mycotoxins aflatoxin, and fumonisin, respectively. Genetic resistance in maize to these fungi and to mycotoxin contamination has been difficult to achieve due to lack of identified resistance genes. The objective of this study was to identify new candidate resistance genes by characterizing their temporal expression in response to infection and comparing expression of these genes with genes known to be associated with plant defense. Fungal colonization and transcriptional changes in kernels inoculated with each fungus were monitored at 4, 12, 24, 48, and 72 h post inoculation (hpi). Maize kernels responded by differential gene expression to each fungus within 4 hpi, before the fungi could be observed visually, but more genes were differentially expressed between 48 and 72 hpi, when fungal colonization was more extensive. Two-way hierarchal clustering analysis grouped the temporal expression profiles of the 5,863 differentially expressed maize genes over all time points into 12 clusters. Many clusters were enriched for genes previously associated with defense responses to either A. flavus or F. verticillioides. Also within these expression clusters were genes that lacked either annotation or assignment to functional categories. This study provided a comprehensive analysis of gene expression of each A. flavus and F. verticillioides during infection of maize kernels, it identified genes expressed early and late in the infection process, and it provided a grouping of genes of unknown function with similarly expressed defense related genes that could inform selection of new genes as targets in breeding strategies.

Overexpression of a Pathogenesis-Related Protein 10 Enhances Biotic and Abiotic Stress Tolerance in Rice

Pathogenesis-related proteins play multiple roles in plant development and biotic and abiotic stress tolerance. Here, we characterize a rice defense related gene named "jasmonic acid inducible pathogenesis-related class 10" (JIOsPR10) to gain an insight into its functional properties. Semi-quantitative RT-PCR analysis showed up-regulation of JIOsPR10 under salt and drought stress conditions. Constitutive over-expression JIOsPR10 in rice promoted shoot and root development in transgenic plants, however, their productivity was unaltered. Further experiments exhibited that the transgenic plants showed reduced susceptibility to rice blast fungus, and enhanced salt and drought stress tolerance as compared to the wild type. A comparative proteomic profiling of wild type and transgenic plants showed that overexpression of JIOsPR10 led to the differential modulation of several proteins mainly related with oxidative stresses, carbohydrate metabolism, and plant defense. Taken together, our findings suggest that JIOsPR10 plays important roles in biotic and abiotic stresses tolerance probably by activation of stress related proteins.

Multiple Patterns of Regulation and Overexpression of a Ribonuclease-Like Pathogenesis-Related Protein Gene, OsPR10a, Conferring Disease Resistance in Rice and Arabidopsis

An abundant 17 kDa RNase, encoded by OsPR10a (also known as PBZ1), was purified from P_i-starved rice suspension-cultured cells. Biochemical analysis showed that the range of optimal temperature for its RNase activity was 40–70°C and the optimum pH was 5.0. Disulfide bond formation and divalent metal ion Mg²⁺ were required for the RNase activity. The expression of OsPR10a::GUS in transgenic rice was induced upon phosphate (P_i) starvation, wounding, infection by the pathogen Xanthomonas oryzae pv. oryzae (Xoo), leaf senescence, anther, style, the style-ovary junction, germinating embryo and shoot. We also provide first evidence in whole-plant system, demonstrated that OsPR10a-overexpressing in rice and Arabidopsis conferred significant level of enhanced resistance to infection by the pathogen Xoo and Xanthomona campestris pv. campestris (Xcc), respectively. Transgenic rice and Arabidopsis overexpressing OsPR10a significantly increased the length of primary root under phosphate deficiency (-P_i) condition. These results showed that OsPR10a might play multiple roles in phosphate recycling in phosphate-starved cells and senescing leaves, and could improve resistance to pathogen infection and/or against chewing insect pests. It is possible that P_i acquisition or homeostasis is associated with plant disease resistance. Our findings suggest that gene regulation of OsPR10a could act as a good model system to unravel the mechanisms behind the correlation between P_i starvation and plant-pathogen interactions, and also provides a potential application in crops disease resistance.

Molecular Cloning and Expression Analysis of hyp-1 Type PR-10 Family Genes in Hypericum perforatum

Hypericum perforatum L. is an important medicinal plant for the treatment of depression. The plant contains bioactive hypericins that accumulate in dark glands present especially in reproductive parts of the plant. In this study, pathogenesis-related class 10 (PR-10) family genes were identified in H. perforatum, including three previously unidentified members with sequence homology to hyp-1, a phenolic coupling protein that has earlier been suggested to participate in biosynthesis and binding/transportation of hypericin. The PR-10 genes showed constitutive but variable expression patterns in different H. perforatum tissues. They were all expressed at relatively high levels in leaves, variably in roots and low levels in stem and reproductive parts of the plant with no specific association with dark glands. The gene expression was up-regulated in leaves after salicylic acid, abscisic acid and wounding treatments but with variable levels. To study exact location of the gene expression, in situ hybridization of hyp-1 transcripts was performed and the accumulation of the Hyp-1 protein was examined in various tissues. The presence of Hyp-1 protein in H. perforatum tissues mostly paralleled with the mRNA levels. In situ RNA hybridization localized the hyp-1 transcripts predominantly in vascular tissues in root and stem, while in leaf the mRNA levels were high also in mesophyll cells in addition to vasculature. Our results indicate that the studied PR-10 genes are likely to contribute to the defense responses in H. perforatum. Furthermore, despite the location of the hyp-1 transcripts in vasculature, no support for the transportation of the Hyp-1 protein to dark glands was found in the current study. The present results together with earlier data question the role of the hyp-1 as a key gene responsible for the hypericin biosynthesis in dark glands of H. perforatum.

High efficiency transformation of banana [Musa acuminata L. cv. Matti (AA)] for enhanced tolerance to salt and drought stress through overexpression of a peanut salinity-induced pathogenesis-related class 10 protein

Bananas and plantains (Musa spp. L.) are important subsistence crops and premium export commodity in several countries, and susceptible to a wide range of environmental and biotic stress conditions. Here, we report efficient, rapid, and reproducible Agrobacterium-mediated transformation and regeneration of an Indian niche cultivar of banana [M. acuminata cv. Matti (AA)]. Apical meristem-derived highly proliferative multiple shoot clump (MSC) explants were transformed with the Agrobacterium strain EHA105 harboring a binary vector pCAMBIA-1301 carrying hptII and uidA. Sequential agro-infiltration (10 min, 400 mmHg), infection (additional 35 min, Agrobacterium density A 600 = 0.8) and co-cultivation (18 h) regimen in 100 µM acetosyringone containing liquid medium were critical factors yielding high transformation efficiency (~81 %) corroborated by transient GUS expression assay. Stable transgenic events were recovered following two cycles of meristem initiation and selection on hygromycin containing medium. Histochemical GUS assay in several tissues of transgenic plants and molecular analyses confirmed stable integration and expression of transgene. The protocol described here allowed recovery of well-established putative transgenic plantlets in as little as 5 months. The transgenic banana plants could be readily acclimatized under greenhouse conditions, and were phenotypically similar to the wild-type untransformed control plants (WT). Transgenic plants overexpressing Salinity-Induced Pathogenesis-Related class 10 protein gene from Arachis hypogaea (AhSIPR10) in banana cv. Matti (AA) showed better photosynthetic efficiency and less membrane damage (P < 0.05) in the presence of NaCl and mannitol in comparison to WT plants suggesting the role of AhSIPR10 in better tolerance of salt stress and drought conditions.

Induction of systemic resistance in Panax ginseng against Phytophthora cactorum by native Bacillus amyloliquefaciens HK34

BACKGROUND

Korean ginseng (Panax ginseng Meyer) is a perennial herb prone to various root diseases, with Phytophthora cactorum being considered one of the most dreaded pathogens. P. cactorum causes foliar blight and root rot. Although chemical pesticides are available for disease control, attention has been shifted to viable, eco-friendly, and cost-effective biological means such as plant growth-promoting rhizobacteria (PGPR) for control of diseases.

METHODS

Native Bacillus amyloliquefaciens strain HK34 was isolated from wild ginseng and assessed as a biological control agent for ginseng. Leaves from plants treated with HK34 were analyzed for induced systemic resistance (ISR) against P. cactorum in square plate assay. Treated plants were verified for differential expression of defense-related marker genes using quantitative reverse transcription polymerase chain reaction.

RESULTS

A total of 78 native rhizosphere bacilli from wild P. ginseng were isolated. One of the root-associated bacteria identified as B. amyloliquefaciens strain HK34 effectively induced resistance against P. cactorum when applied as soil drench once (99.1% disease control) and as a priming treatment two times in the early stages (83.9% disease control). A similar result was observed in the leaf samples of plants under field conditions, where the percentage of disease control was 85.6%. Significant upregulation of the genes PgPR10, PgPR5, and PgCAT in the leaves of plants treated with HK34 was observed against P. cactorum compared with untreated controls and only pathogen-treated plants.

CONCLUSION

The results of this study indicate HK34 as a potential biocontrol agent eliciting ISR in ginseng against P. cactorum.

Isolation and Characterization of a Novel Pathogenesis-Related Protein Gene (GmPRP) with Induced Expression in Soybean (Glycine max) during Infection with Phytophthora sojae

Pathogenesis-related proteins (PR proteins) play crucial roles in the plant defense system. A novel PRP gene was isolated from highly resistant soybean infected with Phytophthora sojae (P. sojae) and was named GmPRP (GenBank accession number: KM506762). The amino acid sequences of GmPRP showed identities of 74%, 73%, 72% and 69% with PRP proteins from Vitis vinifera, Populus trichocarpa, Citrus sinensis and Theobroma cacao, respectively. Quantitative real-time reverse transcription PCR (qRT-PCR) data showed that the expression of GmPRP was highest in roots, followed by the stems and leaves. GmPRP expression was upregulated in soybean leaves infected with P. sojae. Similarly, GmPRP expression also responded to defense/stress signaling molecules, including salicylic acid (SA), ethylene (ET), abscisic acid (ABA) and jasmonic acid (JA). GmPRP was localized in the cell plasma membrane and cytoplasm. Recombinant GmPRP protein exhibited ribonuclease activity and significant inhibition of hyphal growth of P. sojae 1 in vitro. Overexpression of the GmPRP gene in T2 transgenic tobacco and T2 soybean plants resulted in enhanced resistance to Phytophthora nicotianae (P. nicotianae) and P. sojae race 1, respectively. These results indicated that the GmPRP protein played an important role in the defense of soybean against P. sojae infection.

ZmGns, a maize class I β-1,3-glucanase, is induced by biotic stresses and possesses strong antimicrobial activity

Plant β-1,3-glucanases are members of the pathogenesis-related protein 2 (PR-2) family, which is one of the 17 PR protein families and plays important roles in biotic and abiotic stress responses. One of the differentially expressed proteins (spot 842) identified in a recent proteomic comparison between five pairs of closely related maize (Zea mays L.) lines differing in aflatoxin resistance was further investigated in the present study. Here, the corresponding cDNA was cloned from maize and designated as ZmGns. ZmGns encodes a protein of 338 amino acids containing a potential signal peptide. The expression of ZmGns was detectible in all tissues studied with the highest level in silks. ZmGns was significantly induced by biotic stresses including three bacteria and the fungus Aspergillus flavus. ZmGns was also induced by most abiotic stresses tested and growth hormones including salicylic acid. In vivo, ZmGns showed a significant inhibitory activity against the bacterial pathogen Pseudomonas syringae pv. tomato DC3000 and fungal pathogen Botrytis cinerea when it overexpressed in Arabidopsis. Its high level of expression in the silk tissue and its induced expression by phytohormone treatment, as well as by bacterial and fungal infections, suggest it plays a complex role in maize growth, development, and defense.

Discovery and confirmation of genes/proteins associated with maize aflatoxin resistance

Maize (Zea mays L.) is one of the major crops susceptible to Aspergillus flavus infection and subsequent aflatoxin contamination. Many earlier studies indicated the roles of kernel proteins, especially constitutively expressed proteins, in maize resistance to A. flavus infection and aflatoxin production. In this review, we examined the past and current efforts in identifying maize genes and proteins from kernel, rachis, and silk tissues that may play an important role in resistance to A. flavus infection and aflatoxin contamination, as well as the efforts in determining the importance or involvement of them in maize resistance through biochemical, molecular and genetics studies. Through these studies, we gained a better understanding of host resistance mechanism: resistant lines appear to either express some stress-related and antifungal proteins at higher levels in endosperm, embryo, rachis and silk tissues before A. flavus infection or induce the expression of these proteins much faster compared to susceptible maize lines. In addition, we summarised several recent efforts in enhancing maize resistance to aflatoxin contamination using native genes from maize or heterologous and synthetic genes from other sources as well as from A. flavus. These efforts to either suppress A. flavus growth or aflatoxin production, have all shown some promising preliminary success. For example, maize plants transformed with an ?-amylase inhibitor protein from Lablab purpurea showed reduced aflatoxin levels by 56% in kernel screening assays. The antifungal potentials of transgenic maize plants expressing synthetic lytic peptides, such as cecropin-based D4E1 or tachyplesin-based AGM peptides with demonstrated anti-flavus activity (IC50 = 2.5 to 10 ?M), are yet to be assayed. Further investigation in these areas may provide a more cost-effective alternative to biocontrol in managing aflatoxin contamination in maize and other susceptible crops.

Quantitative Proteomics of the Root of Transgenic Wheat Expressing TaBWPR-1.2 Genes in Response to Waterlogging

Once candidate genes are available, the application of genetic transformation plays a major part to study their function in plants for adaptation to respective environmental stresses, including waterlogging (WL). The introduction of stress-inducible genes into wheat remains difficult because of low transformation and plant regeneration efficiencies and expression variability and instability. Earlier, we found two cDNAs encoding WL stress-responsive wheat pathogenesis-related proteins 1.2 (TaBWPR-1.2), TaBWPR-1.2#2 and TaBWPR-1.2#13. Using microprojectile bombardment, both cDNAs were introduced into "Bobwhite". Despite low transformation efficiency, four independent T₂ homozygous lines for each gene were isolated, where transgenes were ubiquitously and variously expressed. The highest transgene expression was obtained in Ubi:TaBWPR-1.2#2 L#11a and Ubi:TaBWPR-1.2#13 L#4a. Using quantitative proteomics, the root proteins of L#11a were analyzed to explore possible physiological pathways regulated by TaBWPR-1.2 under normal and waterlogged conditions. In L#11a, the abundance of proteasome subunit alpha type-3 decreased under normal conditions, whereas that of ferredoxin precursor and elongation factor-2 increased under waterlogged conditions in comparison with normal plants. Proteomic results suggest that L#11a is one of the engineered wheat plants where TaBWPR-1.2#2 is most probably involved in proteolysis, protein synthesis and alteration in the energy pathway in root tissues via the above proteins in order to gain metabolic adjustment to WL.

Molecular characteristics and biochemical functions of VpPR10s from Vitis pseudoreticulata associated with biotic and abiotic stresses

Grapes are one of the world's oldest and most important fruit crops. They are of high economic value in many countries, but the susceptibility of the dominant winegrape species Vitis vinifera to fungal disease is a significant problem. The Chinese wild grape species are a rich source of disease-resistance genes and these can be used to discover how disease resistance in V. vinifera grapevines might be enhanced. Pathogenesis-related (PR) 10 proteins are involved in the disease-response. Here, we use the genomic DNA of the Chinese wild species Vitis pseudoreticulata accession "Baihe-35-1" as the template to design specific primers based on VvPR10s sequences. We used overlap extension PCR to obtain the sequences: VpPR10.4, VpPR10.6, VpPR10.7 and VpPR10.9. The coding sequences of the VpPR10s were then cloned into the pGEX-4T-1 vector. The purified proteins VpPR10.4, VpPR10.6, VpPR10.7 and VpPR10.9 were used to analyse nuclease activity. Meanwhile, functional analysis of VpPR10s under different biotic and abiotic stresses was carried out to further clarify the disease-resistance mechanisms of the Chinese wild grapevine VpPR10 genes. The analysis of protein structure indicates that VpPR10.4 and VpPR10.7 had the P-loop domain and the Bet v 1 motif, which are a consistent feature of plant PR10. However, there was no P-loop domain or Bet v 1 motif in VpPR10.9 and we could not find the Bet v 1 motif in VpPR10.6. The results of the nuclease activity assay and of the functional analyses of VpPR10s under different biotic and abiotic stresses also confirm that VpPR10.4 and VpPR10.7 proteins have marked RNase, DNase, anti-fungal activities and respond to abiotic stresses. The VpPR10.6 and VpPR10.9 proteins do not have these activities and functions.

Protein profiles reveal diverse responsive signaling pathways in kernels of two maize inbred lines with contrasting drought sensitivity

Drought stress is a major factor that contributes to disease susceptibility and yield loss in agricultural crops. To identify drought responsive proteins and explore metabolic pathways involved in maize tolerance to drought stress, two maize lines (B73 and Lo964) with contrasting drought sensitivity were examined. The treatments of drought and well water were applied at 14 days after pollination (DAP), and protein profiles were investigated in developing kernels (35 DAP) using iTRAQ (isobaric tags for relative and absolute quantitation). Proteomic analysis showed that 70 and 36 proteins were significantly altered in their expression under drought treatments in B73 and Lo964, respectively. The numbers and levels of differentially expressed proteins were generally higher in the sensitive genotype, B73, implying an increased sensitivity to drought given the function of the observed differentially expressed proteins, such as redox homeostasis, cell rescue/defense, hormone regulation and protein biosynthesis and degradation. Lo964 possessed a more stable status with fewer differentially expressed proteins. However, B73 seems to rapidly initiate signaling pathways in response to drought through adjusting diverse defense pathways. These changes in protein expression allow for the production of a drought stress-responsive network in maize kernels.

Isolation and characterization of a pathogenesis-related protein 10 gene (GmPR10) with induced expression in soybean (Glycine max) during infection with Phytophthora sojae

In previous study, a cDNA library enriched for mRNAs encoding ESTs that increased in abundance during infection with Phytophthora sojae was constructed by suppression subtractive hybridization from leaf tissues of a high resistant soybean, and an EST homologous to the class 10 of pathogenesis-related (PR) proteins was identified to be up-regulated by microarray and real-time PCR. Here, the full-length cDNA (termed GmPR10, GenBank accession number FJ960440; ADC31789.1) of the EST was isolated by rapid amplification of cDNA ends, and contains an open reading frame of 474 bp. The GmPR10 protein included a "P-loop'' motif. The constitutive transcript abundance of GmPR10 in soybean was the highest in leaves, followed by roots and stems. Further analysis showed that GmPR10 mRNA abundance was increased during infection with P. sojae following leaf treatments with gibberellin (GA3), hydrogen peroxide (H2O2), salicylic acid (SA), and abscisic acid (ABA). The dialytically renatured GmPR10 protein significantly inhibited P. sojae hyphal growth and exhibited RNase activity. Transgenic tobacco and soybean plants overexpressing GmPR10 showed increased resistance to P. nicotianae Breda and P. sojae, respectively. These results suggest that the GmPR10 protein plays an important role in host defense against P. sojae infection. To the best of our knowledge, this is the first report on the functional characterization of a PR10 protein from soybean in defense against P. sojae.