The group I GH3 family genes encoding JA-Ile synthetase act as positive regulator in the resistance of rice to Xanthomonas oryzae pv. oryzae

Molecular insight into auxin signaling and associated network modulating stress responses in rice

Phytohormones are vital regulators of various signaling networks in plants. Among different phytohormones, auxin has been thoroughly studied for its role in regulating plants' growth, development, and stress response. One major function of auxin is modulating the developmental processes in response to environmental cues. Although extensive studies on Arabidopsis have advanced the knowledge of auxin biology, several studies on rice have uncovered key players regulated by auxin that play critical roles in coordinating auxin homeostasis and signaling involved in defense response. The emerging knowledge on auxin biology, auxin-regulated gene expression, and auxin-signaling in rice during various environmental stresses has provided insights into the possible mechanism of rice susceptibility or resistance to different abiotic and biotic stresses. The current review enumerates the possible mechanisms of stress-induced auxin homeostasis in rice. In addition, we provide an overview of the state of knowledge on auxin-mediated defense signaling in rice, highlighting its pivotal role in stress response. In particular, we discuss the auxin pathways and the dynamic regulation in response to biotic and abiotic stress. We highlight the novel findings in the diversity of auxin signaling in the model plant Arabidopsis with an aim to emphasize the need to translate these findings into agronomically and economically important cereals like rice. Addressing the complexity of auxin induction, signaling, and its associated molecular network, an in-depth investigation in rice is required to comprehend auxin-mediated spatial-temporal regulation of developmental processes during stress.

Exploring the response of yellow lupine (Lupinus luteus L.) root to drought mediated by pathways related to phytohormones, lipid, and redox homeostasis

BACKGROUND

Yellow lupine (Lupinus luteus L.) is a high-protein crop of considerable economic and ecological significance. It has the ability to fix atmospheric nitrogen in symbiosis with Rhizobium, enriching marginal soils with this essential nutrient and reducing the need for artificial fertilizers. Additionally, lupine produces seeds with a high protein content, making it valuable for animal feed production. However, drought negatively affects lupine development, its mutualistic relationship with bacteria, and overall yield. To understand how lupine responds to this stress, global transcriptome sequencing was conducted, along with in-depth biochemical, chromatography, and microscopy analyses of roots subjected to drought. The results presented here contribute to strategies aimed at mitigating the effects of water deficit on lupine growth and development.

RESULTS

Based on RNA-seq, drought-specific genes were identified and annotated to biological pathways involved in phytohormone biosynthesis/signaling, lipid metabolism, and redox homeostasis. Our findings indicate that drought-induced disruption of redox balance characterized by the upregulation of reactive oxygen species (ROS) scavenging enzymes, coincided with the accumulation of lipid-metabolizing enzymes, such as phospholipase D (PLD) and lipoxygenase (LOX). This disruption also led to modifications in lipid homeostasis, including increased levels of triacylglycerols (TAG) and free fatty acids (FFA), along with a decrease in polar lipid content. Additionally, the stress response involved alterations in the transcriptional regulation of the linolenic acid metabolism network, resulting in changes in the composition of fatty acids containing 18 carbons.

CONCLUSION

The first comprehensive global transcriptomic profiles of lupine roots, combined with the identification of key stress-responsive molecules, represent a significant advancement in understanding lupine's responses to abiotic stress. The increased expression of the Δ12DESATURASE gene and enhanced PLD activity lead to higher level of linoleic acid (18:2), which is subsequently oxidized by LOX, resulting in membrane damage and malondialdehyde (MDA) accumulation. Oxidative stress elevates the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT), while the conversion of FFAs into TAGs provides protection against ROS. This research offers valuable molecular and biochemical candidates with significant potential to enhance drought tolerance . It enables innovative strategies in lupine breeding and crop improvement to address critical agricultural challenges.

MdABCI17 acts as a positive regulator to enhance apple resistance to Botryosphaeria dothidea

The ATP-binding cassette (ABC) superfamily is involved in numerous complex biological processes. However, the understanding of ABCs in plant pathogen defense, particularly against Botryosphaeria dothidea, remains limited. In this study, we identified MdABCI17 that plays a positive role in apple resistance to B. dothidea. Overexpression of MdABCI17 significantly enhanced the resistance of apple calli and fruits to B. dothidea. Our findings revealed that the jasmonic acid (JA) content and the expression of genes associated with JA biosynthesis and signal transduction were higher in stable MdABCI17-overexpressing apple calli than that of wild-type after inoculation with B. dothidea. Similar results were obtained for apple fruits with transient overexpression of MdABCI17. Our research indicates that MdABCI17 enhances apple resistance to B. dothidea through the JA signaling pathway. We further determined that MdABCI17 plays a crucial role in the apple's response to JA signaling. Moreover, exogenous methyl jasmonate (MeJA) treatment significantly enhanced the effectiveness of MdABCI17 in boosting apple resistance to B. dothidea. We proposed a positive feedback regulatory loop between MdABCI17-mediated apple resistance to B. dothidea and JA signal. In summary, our study offers new insights into the role of ABC superfamily members in the control of plant disease resistance.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11032-024-01501-9.

Jasmonic acid (JA)-mediating MYB transcription factor1, JMTF1, coordinates the balance between JA and auxin signalling in the rice defence response

The plant hormone jasmonic acid (JA) is a signalling compound involved in the regulation of cellular defence and development in plants. In this study, we investigated the roles of a JA-responsive MYB transcription factor, JMTF1, in the JA-regulated defence response against rice bacterial blight caused by Xanthomonas oryzae pv. oryzae (Xoo). JMTF1 did not interact with any JASMONATE ZIM-domain (JAZ) proteins. Transgenic rice plants overexpressing JMTF1 showed a JA-hypersensitive phenotype and enhanced resistance against Xoo. JMTF1 upregulated the expression of a peroxidase, OsPrx26, and monoterpene synthase, OsTPS24, which are involved in the biosynthesis of lignin and antibacterial monoterpene, γ-terpinene, respectively. OsPrx26 was mainly expressed in the vascular bundle. Transgenic rice plants overexpressing OsPrx26 showed enhanced resistance against Xoo. In addition to the JA-hypersensitive phenotype, the JMTF1-overexpressing rice plants showed a typical auxin-related phenotype. The leaf divergence and shoot gravitropic responses were defective, and the number of lateral roots decreased significantly in the JMTF1-overexpressing rice plants. JMTF1 downregulated the expression of auxin-responsive genes but upregulated the expression of OsIAA13, a suppressor of auxin signalling. The rice gain-of-function mutant Osiaa13 showed high resistance against Xoo. Transgenic rice plants overexpressing OsEXPA4, a JMTF1-downregulated auxin-responsive gene, showed increased susceptibility to Xoo. JMTF1 is selectively bound to the promoter of OsPrx26 in vivo. These results suggest that JMTF1 positively regulates disease resistance against Xoo by coordinating crosstalk between JA- and auxin-signalling in rice.

Evolutionary Analysis of the Melon (Cucumis melo L.) GH3 Gene Family and Identification of GH3 Genes Related to Fruit Growth and Development

The indole-3-acetic acid (IAA) auxin is an important endogenous hormone that plays a key role in the regulation of plant growth and development. In recent years, with the progression of auxin-related research, the function of the Gretchen Hagen 3 (GH3) gene has become a prominent research topic. However, studies focusing on the characteristics and functions of melon GH3 family genes are still lacking. This study presents a systematic identification of melon GH3 gene family members based on genomic data. The evolution of melon GH3 family genes was systematically analyzed by means of bioinformatics, and the expression patterns of the GH3 family genes in different melon tissues during different fruit developmental stages and with various levels of 1-naphthaleneacetic acid (NAA) induction were analyzed with transcriptomics and RT-qPCR. The melon genome contains 10 GH3 genes distributed across seven chromosomes, and most of these genes are expressed in the plasma membrane. According to evolutionary analysis and the number of GH3 family genes, these genes can be divided into three subgroups, and they have been conserved throughout the evolution of melon. The melon GH3 gene has a wide range of expression patterns across distinct tissue types, with expression generally being higher in flowers and fruit. Through promoter analysis, we found that most cis-acting elements contained light- and IAA-responsive elements. Based on the RNA-seq and RT-qPCR analyses, it can be speculated that CmGH3-5, CmGH3-6 and CmGH3-7 may be involved in the process of melon fruit development. In conclusion, our findings suggest that the GH3 gene family plays an important role in the development of melon fruit. This study provides an important theoretical basis for further research on the function of the GH3 gene family and the molecular mechanism underlying the development of melon fruit.

Multi-omics analysis provides insight into the phytotoxicity of chicken manure and cornstalk on seed germination

To minimize environmental risks and the phytotoxic influence of organic materials on crop growth, it is necessary to test their phytotoxicity and maturity when they were used in farmland. However, the stress response of seed germination to chicken manure and cornstalks is not clear. This study used multi-omics analysis to investigate the inhibition mechanism of seed germination by chicken manure and cornstalk. Chicken manure caused destructive inhibition of seed germination with higher phytotoxicity (GI = 0). Cornstalk also had a low GI (8.81 %), while it mainly inhibited radicle growth (RL = 9.39 %) rather than seed germination (GR = 93.33 %). The response of radish seed germination to chicken manure and cornstalk phytotoxic stresses was accompanied by metabolic adjustments of storage substance accumulation, antioxidant enzyme activity change, phytohormone induction, and expression of specific proteins and gene regulation. Combined transcriptomic and proteomic analysis revealed that differential expression of 13,090 (5944 upregulated/7146 downregulated) and 3850 (2389 upregulated/1461 downregulated) genes (DEGs), and 1041 (82 upregulated/932 downregulated) and 575 (111 upregulated/464 downregulated) proteins (DEPs) at chicken manure and cornstalk treatment, respectively. Most down-regulated genes and proteins were involved in phenylpropanoid biosynthesis under chicken manure stress, which caused irreversible inhibition of seed germination. Down-regulation of phytohormone signal transduction-related genes under cornstalk stress resulted in inhibition of radicle growth, but the inhibitory stress was restorable. These findings provide new insight into the phytotoxicity of livestock manure and cornstalk on seed germination.

Genome-Wide Identification of Auxin-Responsive GH3 Gene Family in Saccharum and the Expression of ScGH3-1 in Stress Response

Gretchen Hagen3 (GH3), one of the three major auxin-responsive gene families, is involved in hormone homeostasis in vivo by amino acid splicing with the free forms of salicylic acid (SA), jasmonic acid (JA) or indole-3-acetic acid (IAA). Until now, the functions of sugarcane GH3 (SsGH3) family genes in response to biotic stresses have been largely unknown. In this study, we performed a systematic identification of the SsGH3 gene family at the genome level and identified 41 members on 19 chromosomes in the wild sugarcane species, Saccharum spontaneum. Many of these genes were segmentally duplicated and polyploidization was the main contributor to the increased number of SsGH3 members. SsGH3 proteins can be divided into three major categories (SsGH3-I, SsGH3-II, and SsGH3-III) and most SsGH3 genes have relatively conserved exon-intron arrangements and motif compositions. Diverse cis-elements in the promoters of SsGH3 genes were predicted to be essential players in regulating SsGH3 expression patterns. Multiple transcriptome datasets demonstrated that many SsGH3 genes were responsive to biotic and abiotic stresses and possibly had important functions in the stress response. RNA sequencing and RT-qPCR analysis revealed that SsGH3 genes were differentially expressed in sugarcane tissues and under Sporisorium scitamineum stress. In addition, the SsGH3 homolog ScGH3-1 gene (GenBank accession number: OP429459) was cloned from the sugarcane cultivar (Saccharum hybrid) ROC22 and verified to encode a nuclear- and membrane-localization protein. ScGH3-1 was constitutively expressed in all tissues of sugarcane and the highest amount was observed in the stem pith. Interestingly, it was down-regulated after smut pathogen infection but up-regulated after MeJA and SA treatments. Furthermore, transiently overexpressed Nicotiana benthamiana, transduced with the ScGH3-1 gene, showed negative regulation in response to the infection of Ralstonia solanacearum and Fusarium solani var. coeruleum. Finally, a potential model for ScGH3-1-mediated regulation of resistance to pathogen infection in transgenic N. benthamiana plants was proposed. This study lays the foundation for a comprehensive understanding of the sequence characteristics, structural properties, evolutionary relationships, and expression of the GH3 gene family and thus provides a potential genetic resource for sugarcane disease-resistance breeding.

The Mutation of Rice MEDIATOR25, OsMED25, Induces Rice Bacterial Blight Resistance through Altering Jasmonate- and Auxin-Signaling

Rice bacterial blight disease caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most severe diseases of rice. However, the regulatory mechanisms of rice defense against Xoo remain poorly understood. The rice MEDIATOR25, OsMED25—a subunit of the mediator multiprotein complex that acts as a universal adaptor between transcription factors (TFs) and RNA polymerase II—plays an important role in jasmonic acid (JA)-mediated lateral root development in rice. In this study, we found that OsMED25 also plays an important role in JA- and auxin-mediated resistance responses against rice bacterial blight. The osmed25 loss-of-function mutant exhibited high resistance to Xoo. The expression of JA-responsive defense-related genes regulated by OsMYC2, which is a positive TF in JA signaling, was downregulated in osmed25 mutants. Conversely, expression of some OsMYC2-independent JA-responsive defense-related genes was upregulated in osmed25 mutants. Furthermore, OsMED25 interacted with some AUXIN RESPONSE FACTORS (OsARFs) that regulate auxin signaling, whereas the mutated osmed25 protein did not interact with the OsARFs. The expression of auxin-responsive genes was downregulated in osmed25 mutants, and auxin-induced susceptibility to Xoo was not observed in osmed25 mutants. These results indicate that OsMED25 plays an important role in the stable regulation of JA- and auxin-mediated signaling in rice defense response.

Using Transcriptome Analysis to Explore Gray Mold Resistance-Related Genes in Onion (Allium cepa L.)

Gray mold disease caused by Botrytis in onions (Allium cepa L.) during growth and storage negatively affects their yield and quality. Exploring the genes related to gray mold resistance in onion and their application to the breeding of resistant onion lines will support effective and ecological control methods of the disease. Here, the genetic relationship of 54 onion lines based on random amplified polymorphic DNA (RAPD) and in vitro-cultured onion lines infected with gray mold were used for screening resistance and susceptibility traits. Two genetically related onion lines were selected, one with a resistant and one with a susceptible phenotype. In vitro gray mold infection was repeated with these two lines, and leaf samples were collected for gene expression studies in time series. Transcript sequences obtained by RNA sequencing were subjected to DEG analysis, variant analysis, and KEGG mapping. Among the KEGG pathways, ‘α-linoleic acid metabolism’ was selected because the comparison of the time series expression pattern of Jasmonate resistant 1 (JAR1), Coronatine-insensitive protein 1 (COI 1), and transcription factor MYC2 (MYC2) genes between the resistant and susceptible lines revealed its significant relationship with gray-mold-resistant phenotypes. Expression pattern and SNP of the selected genes were verified by quantitative real-time PCR and high-resolution melting (HRM) analysis, respectively. The results of this study will be useful for the development of molecular marker and finally breeding of gray-mold-resistant onions.

The GH3 amidosynthetases family and their role in metabolic crosstalk modulation of plant signaling compounds

The Gretchen Hagen 3 (GH3) genes encoding proteins belonging to the ANL superfamily are widespread in the plant kingdom. The ANL superfamily consists of three groups of adenylating enzymes: aryl- and acyl-CoA synthetases, firefly luciferase, and amino acid-activating adenylation domains of the nonribosomal peptide synthetases (NRPS). GH3s are cytosolic, acidic amidosynthetases of the firefly luciferase group that conjugate auxins, jasmonates, and benzoate derivatives to a wide group of amino acids. In contrast to auxins, which amide conjugates mainly serve as a storage pool of inactive phytohormone or are involved in the hormone degradation process, conjugation of jasmonic acid (JA) results in biologically active phytohormone jasmonyl-isoleucine (JA-Ile). Moreover, GH3s modulate salicylic acid (SA) concentration by conjugation of its precursor, isochorismate. GH3s, as regulators of the phytohormone level, are crucial for normal plant development as well as plant defense response to different abiotic and biotic stress factors. Surprisingly, recent studies indicate that FIN219/JAR1/GH3.11, one of the GH3 proteins, may act not only as an enzyme but is also able to interact with tau-class glutathione S-transferase (GSTU) and constitutive photomorphogenic 1 (COP1) proteins and regulate light and stress signaling pathways. The aim of this work is to summarize our current knowledge of the GH3 family.

Insight into VvGH3 genes evolutional relationship from monocotyledons and dicotyledons reveals that VvGH3-9 negatively regulates the drought tolerance in transgenic Arabidopsis

The Gretchen Hagen3 (GH3) gene family is necessary for growth and development in plants and is regulated by osmotic stress and various hormones. Although it has been reported in many plants, the evolutionary relationship of GH3 in grape has not been systematically analyzed from the perspective of monocotyledonous and dicotyledonous. This study identified and analyzed 188 GH3 genes, which were distinctly divided into 9 subgroups, and found these subgroups have obviously been clustered between monocotyledonous and dicotyledonous. VvGH3-x genes had higher synteny with apple and Arabidopsis than that of rice, and the average Ka/Ks value in monocotyledons was higher than that of dicotyledons. The codon usage index showed that monocotyledons preferred to use G3s, C3s, and GC3s, while dicotyledons preferred to use A3s and T3s. The GH3 genes of grape exhibited different expression patterns in various tissues, different abiotic stresses, and hormonal treatments. The subcellular localization showed that VvGH3-9 was expressed in the nucleus and cytoplasm. Additionally, under 20% PEG treatment, the IAA and ABA contents, relative expression levels of VvGH3-9, relative electrical conductivity (REC), as well as MDA were obviously increased in VvGH3-9 overexpression lines at 72 h. In contrast, compared to WT, the contents of proline and H₂O₂, the activities of POD, SOD, and CAT, and the relative expression levels of drought responsive genes were significantly decreased in overexpressing lines. Collectively, this study provided helpful insight for the evolution of GH3 genes and presented some possibilities to study the functions of GH3 genes in monocotyledons and dicotyledons.

Overexpression of SgGH3.1 from Fine-Stem Stylo (Stylosanthes guianensis var. intermedia) Enhances Chilling and Cold Tolerance in Arabidopsis thaliana

Stylosanthes (stylo) species are commercially significant tropical and subtropical forage and pasture legumes that are vulnerable to chilling and frost. However, little is known about the molecular mechanisms behind stylos' responses to low temperature stress. Gretchen-Hagen 3 (GH3) proteins have been extensively investigated in many plant species for their roles in auxin homeostasis and abiotic stress responses, but none have been reported in stylos. SgGH3.1, a cold-responsive gene identified in a whole transcriptome profiling study of fine-stem stylo (S. guianensis var. intermedia) was further investigated for its involvement in cold stress tolerance. SgGH3.1 shared a high percentage of identity with 14 leguminous GH3 proteins, ranging from 79% to 93%. Phylogenetic analysis classified SgGH3.1 into Group Ⅱ of GH3 family, which have been proven to involve with auxins conjugation. Expression profiling revealed that SgGH3.1 responded rapidly to cold stress in stylo leaves. Overexpression of SgGH3.1 in Arabidopsis thaliana altered sensitivity to exogenous IAA, up-regulated transcription of AtCBF1-3 genes, activated physiological responses against cold stress, and enhanced chilling and cold tolerances. This is the first report of a GH3 gene in stylos, which not only validated its function in IAA homeostasis and cold responses, but also gave insight into breeding of cold-tolerant stylos.

Seed treatment and foliar application of methyl salicylate (MeSA) as a defense mechanism in rice plants against the pathogenic bacterium, Xanthomonas oryzae pv. oryzae

Methyl salicylate (MeSA) is a volatile biological compound synthesized from salicylic acid (SA) and is a plant hormone that helps defend against pests and pathogens. A major bacterial pathogen of rice, Xanthomonas oryzae pv. oryzae (Xoo) causes severe disease. Seed and plant treatments with MeSA can stimulate the defense enzyme peroxidase (POD) in plants. Response of peroxidase activity in rice (Oryza sativa L) cultivars IR 20, IR 50, IR 64, ASD 16, ASD 19 and ADT 46 to MeSA were measured under greenhouse conditions. Treatments of rice seedlings with MeSA at 50 and 100 mg L^-1 significantly upregulated POD expression in the plants. The activity of POD was also significantly upregulated when plants were inoculated with bacterial blight. Effects were stronger in ASD 16, ASD 19 and ADT 46 and were more pronounced in high dose treatment (100 mg L^-1) when inoculated with bacterial blight condition and the effects were dose dependent, although the relationship between dose and rice varieties were not always linear. The pathogenic related (PR) protein bands at 33 kDa and 14 kDa were identified in treatments of 100 mg L^-1 MeSA in the presence of bacterial blight disease. Band intensity was estimated to be twice that of those from pathogen induce MeSA levels in rice plants. These results suggest that treatment with MeSA can significantly increase the POD defense related enzyme by altering the plant physiology in ways that may be beneficial for crop protection.

Transcriptome analysis reveals underlying immune response mechanism of fungal (Penicillium oxalicum) disease in Gastrodia elata Bl. f. glauca S. chow (Orchidaceae)

BACKGROUND

Gastrodia elata Bl. f. glauca S. Chow is a medicinal plant. G. elata f. glauca is unavoidably infected by pathogens in their growth process. In previous work, we have successfully isolated and identified Penicillium oxalicum from fungal diseased tubers of G. elata f. glauca. As a widespread epidemic, this fungal disease seriously affected the yield and quality of G. elata f. glauca. We speculate that the healthy G. elata F. glauca might carry resistance genes, which can resist against fungal disease. In this study, healthy and fungal diseased mature tubers of G. elata f. glauca from Changbai Mountain area were used as experimental materials to help us find potential resistance genes against the fungal disease.

RESULTS

A total of 7540 differentially expressed Unigenes (DEGs) were identified (FDR < 0.01, log2FC > 2). The current study screened 10 potential resistance genes. They were attached to transcription factors (TFs) in plant hormone signal transduction pathway and plant pathogen interaction pathway, including WRKY22, GH3, TIFY/JAZ, ERF1, WRKY33, TGA. In addition, four of these genes were closely related to jasmonic acid signaling pathway.

CONCLUSIONS

The immune response mechanism of fungal disease in G. elata f. glauca is a complex biological process, involving plant hormones such as ethylene, jasmonic acid, salicylic acid and disease-resistant transcription factors such as WRKY, TGA.

Jasmonates-the Master Regulator of Rice Development, Adaptation and Defense

Rice is one of the most important food crops worldwide, as well as the model plant in molecular studies on the cereals group. Many different biotic and abiotic agents often limit rice production and threaten food security. Understanding the molecular mechanism, by which the rice plant reacts and resists these constraints, is the key to improving rice production to meet the demand of an increasing population. The phytohormone jasmonic acid (JA) and related compounds, collectively called jasmonates, are key regulators in plant growth and development. They are also one of the central players in plant immunity against biotic attacks and adaptation to unfavorable environmental conditions. Here, we review the most recent knowledge about jasmonates signaling in the rice crop model. We highlight the functions of jasmonates signaling in many adaptive responses, and also in rice growth and development processes. We also draw special attention to different signaling modules that are controlled by jasmonates in rice.

Jasmonic Acid-Involved OsEDS1 Signaling in Rice-Bacteria Interactions

BACKGROUND

The function of Arabidopsis enhanced disease susceptibility 1 (AtEDS1) and its sequence homologs in other dicots have been extensively studied. However, it is unknown whether rice EDS1 homolog (OsEDS1) plays a role in regulating the rice-pathogen interaction.

RESULTS

In this study, a OsEDS1-knouckout mutant (oseds1) was characterized and shown to have increased susceptibility to Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas oryzae pv. oryzicola (Xoc), suggesting the positive role of OsEDS1 in regulating rice disease resistance. However, the following evidence suggests that OsEDS1 shares some differences with AtEDS1 in its way to regulate the host-pathogen interactions. Firstly, OsEDS1 modulates the rice-bacteria interactions involving in jasmonic acid (JA) signaling pathway, while AtEDS1 regulates Arabidopsis disease resistance against biotrophic pathogens depending on salicylic acid (SA) signaling pathway. Secondly, introducing AtEDS1 could reduce oseds1 mutant susceptibility to Xoo rather than to Xoc. Thirdly, exogenous application of JA and SA cannot complement the susceptible phenotype of the oseds1 mutant, while exogenous application of SA is capable of complementing the susceptible phenotype of the ateds1 mutant. Finally, OsEDS1 is not required for R gene mediated resistance, while AtEDS1 is required for disease resistance mediated by TIR-NB-LRR class of R proteins.

CONCLUSION

OsEDS1 is a positive regulator in rice-pathogen interactions, and shares both similarities and differences with AtEDS1 in its way to regulate plant-pathogen interactions.

Rice group I GH3 gene family, positive regulators of bacterial pathogens

Plant GH3 genes play pivotal roles in biotic stress through involving in hormonal homeostasis by conjugation to amino acids of the free-form of salicylic acid, jasmonic acid (JA) or indole-3-acetic acid. We recently showed that rice group I GH3 gene family, with four members, are the functional JA-Ile synthetases and positively mediated rice resistance to Xanthomonas oryzae pv. oryzae (Xoo). Here, we further found that these four genes are also positive regulators conferring resistance to Xanthomonas oryzae pv. oryzicola (Xoc), the devastating bacterial pathogen of rice. The transcript of these four genes were all activated upon Xoc invasion. The overexpressing plants showed less lesion length in comparison with wild type plant accompanying with higher pathogenesis-related genes accumulation, while the triple and quadruple suppressing plants showed susceptible to Xoc with less pathogenesis-related genes accumulation. Previous and present work demonstrate that rice group I GH3 family genes act as positive regulators in the resistance to Xoo and Xoc.