Rice blast disease, caused by Magnaporthe oryzae, threatens global food security. The rice blast pathosystem is a longstanding model system for understanding plant-microbe interactions. In order to elucidate the coevo...Rice blast disease, caused by Magnaporthe oryzae, threatens global food security. The rice blast pathosystem is a longstanding model system for understanding plant-microbe interactions. In order to elucidate the coevolution of the host and pathogen, and provide the appropriate methods for preventing or controlling rice blast disease, researchers have focused on the evolution of virulence factors and resistance genes. Thus far, more than 30 rice blast resistance（R） genes and 12 avirulence（Avr） genes have been cloned. This review summarizes the cloned rice blast R genes, cloned Avr genes of M. oryzae and the interaction between them. This discussion also considers some of the major unanswered questions concerning this pathosystem and the opportunities for future investigations.展开更多
Xanthomonas oryzae pv.oryzae,the causal agent of bacterial blight in rice,interacts with rice plants in a gene-for-gene manner.The specificity of the interaction is dictated by avirulence(avr) genes in the pathogen an...Xanthomonas oryzae pv.oryzae,the causal agent of bacterial blight in rice,interacts with rice plants in a gene-for-gene manner.The specificity of the interaction is dictated by avirulence(avr) genes in the pathogen and resistance(R) genes in the host.To date,no avr genes that correspond to recessive R genes have been isolated.We isolated an avrBs3/pthA family gene,avrxa5,from our previously isolated clone p58,which was originally from strain JXOIII.The avrxa5 gene converted the PXO99A strain from compatible to incompatible in rice cultivars containing the recessive xa5 gene,but not in those containing the dominant Xa5 gene.Sequencing indicated that avrxa5,which is highly similar to members of the avrBs3/pthA family,encodes a protein of 1238 amino acid residues with a conserved carboxy-terminal region containing three nuclear localization signals and a transcription activation domain.It has 19.5 34-amino-acid direct repeats,but the 13th amino acid is missing in the fifth and ninth repetitive units.Domain swapping of the repetitive regions between avrxa5 and avrXa7 changed the avirulence specificity of the genes in xa5 and Xa7 rice lines,respectively.This indicates that avrxa5 is distinct from previously characterized avrBs3/pthA members.The specificity of avrxa5 toward recessive xa5 in rice could help us better understand the molecular mechanisms of plant-pathogen specific interactions.展开更多
Rice blast,caused by Magnaporthe oryzae,is one of the most devastating diseases of rice.During infection,M.oryzae secretes effectors to facilitate blast development.Among these effectors,the avirulence factor AvrPi9 i...Rice blast,caused by Magnaporthe oryzae,is one of the most devastating diseases of rice.During infection,M.oryzae secretes effectors to facilitate blast development.Among these effectors,the avirulence factor AvrPi9 is recognized by Pi9,a broad-spectrum blast resistance protein that triggers Pi9-mediated resistance in rice.However,little is known about the interaction between AvrPi9 and Pi9 and how AvrPi9 exerts virulence to promote infection.In this study,we found that ectopic expression of AvrPi9 in the Pi9-lacking cultivar TP309 suppressed basal resistance against M.oryzae.Furthermore,we identified an AvrPi9-interacting protein in rice,which we named OsRGLG5,encoding a functional RING-type E3 ubiquitin ligase.During infection,AvrPi9 was ubiquitinated and degraded by OsRGLG5.Meanwhile,AvrPi9 affected the stability of OsRGLG5.Infection assays revealed that OsRGLG5 is a positive regulator of basal resistance against M.oryzae,but it is not essential for Pi9-mediated blast resistance in rice.In conclusion,our results revealed that OsRGLG5 is targeted by the M.oryzae effector AvrPi9 and positively regulates basal resistance against rice blast.展开更多
Avirulence effectors(Avrs),encoded by plant pathogens,can be recognized by plants harboring the corresponding resistance proteins,thereby initiating effector-triggered immunity(ETI).In susceptible plants,however,Avrs ...Avirulence effectors(Avrs),encoded by plant pathogens,can be recognized by plants harboring the corresponding resistance proteins,thereby initiating effector-triggered immunity(ETI).In susceptible plants,however,Avrs can function as effectors,facilitating infection via effector-triggered susceptibility(ETS).Mechanisms of Avr-mediated ETS remain largely unexplored.Here we report that the Magnaporthe oryzae effector Avr-PikD enters rice cells via the canonical cytoplasmic secretion pathway and suppresses rice basal defense.Avr-PikD interacts with an LSD1-like transcriptional activator AKIP30 of rice,and AKIP30 is also a positive regulator of rice immunity,whereas Avr-PikD impedes its nuclear localization and suppresses its transcriptional activity.In summary,M.oryzae delivers Avr-PikD into rice cells to facilitate ETS by inhibiting AKIP30-mediated transcriptional regulation of immune response against M.oryzae.展开更多
The AVR-Pita1 gene,from the Chinese isolate O-137 of Magnaporthe oryzae,is an effector that determines the efficacy of the Pi-ta rice blast resistance gene.In the present study,the avirulence function of AVR-Pita1 was...The AVR-Pita1 gene,from the Chinese isolate O-137 of Magnaporthe oryzae,is an effector that determines the efficacy of the Pi-ta rice blast resistance gene.In the present study,the avirulence function of AVR-Pita1 was induced by transformation of field isolates(TM2,ZN19,B2 and B8)that originally were collected from the U.S.and are virulent on Pi-ta-carrying rice cultivars.The presence of AVR-Pita1 from O-137 in independent transformants was detected by PCR using AVR-Pita1 specific primers and verified by DNA sequencing and Southern blot analysis using the AVR-Pita1 coding region as a probe.The results of pathogenicity assays showed that the AVR-Pita1-transformed isolates were not able to infect rice cultivars Katy and Drew carrying Pi-ta.Control isolates that were transformed with inserts lacking the AVR-Pita1gene remained virulent.Our findings demonstrate that AVR-Pita1 can be used to induce novel gene-specific blast resistance in nature.展开更多
Puccinia striiformis f. sp. tritici (Pst) is one of the pathogenic fungi on wheat, caused stripe rust that is a great threat for wheat production all over the world. Intensive efforts have been made to study genetics ...Puccinia striiformis f. sp. tritici (Pst) is one of the pathogenic fungi on wheat, caused stripe rust that is a great threat for wheat production all over the world. Intensive efforts have been made to study genetics of wheat resistance to this disease, but few on avirulence of the pathogen due mainly to the nature of obligate biotrophism and the lack of systems for studying its genetics and molecular manipulations. To overcome these limitations, a natural Pst population comprising 352 isolates representative of a diverse virulence spectrum was genotyped using 97 secreted protein-single nucleotide polymorphism (SP-SNP) markers to identify candidate avirulence genes using association analysis. Among avirulence genes corresponding to 19 resistance genes, significantly associated SP-SNP markers were detected for avirulence genes AvYr1, AvYr2, AvYr6, AvYr7, AvYr8, AvYr44, AvYrExp2, AvYrSP, and AvYrTye. These results indicate that association analysis can be used to identify markers for avirulence genes. This study has laid the foundation for developing more SP-SNPs for mapping avirulence genes using segregating populations that can be generated through sexual reproduction on alternate hosts of the pathogen.展开更多
Understanding the sequence diversity of rice blast resistance genes is important for breeding new resistant rice cultivars against the rice blast fungusMagnaporthe oryzae. In this study, we selected 24 rice cultivars ...Understanding the sequence diversity of rice blast resistance genes is important for breeding new resistant rice cultivars against the rice blast fungusMagnaporthe oryzae. In this study, we selected 24 rice cultivars with different genetic back-grounds to study the alelic diversity of rice blast resistance genesPiz-t, Pitaand Pik. For Piz-t, a total of 17 alelic types were found within the 24 cultivars. Blast inoculations showed that most of the mutations can affect the function of the resistance gene. For Pita, except for the difference at the 918th amino acid, a majority of the 21 mutations were detected among the cultivars. Inoculations with blast isolates carryingAvr-Pita revealed that cultivars with mutations in other sites except for the 918th amino acid did not affect the function of thePita gene. ForPik, a total of six alelic types were found within the 24 cultivars, but ifve of them lost the function of the resistance gene. In addition, we found thatPiz-t, Pita and Pik were expressed constitutively in the 24 rice cultivars and the expression level was not related to resistance. Our results have provided the sequence diversity information of the resistance genesPiz-t, Pita and Pik among the popular rice cultivars grown in the northeast region of China. Keywords：resistance gene, avirulence gene, aleles, function, genetic evolution zae（M. oryzae）, is one of the most destructive diseases in rice production worldwide. Over the years, comprehensive studies on rice blast resistance have been conducted （Silue et al. 1992）. The resistance in newly cultivated rice cultivars to M. oryzae can be lost quickly due to the high level of instability in the genome of the fungus （Bonmanet al. 1992）. Previous studies show that cultivars with durable and broad-spectrum resistance againstM. oryzae carry multiple major resistance （R） and minor resistance genes （Liuet al. 2014）. An effective way to control rice blast disease is, therefore, to breed rice cultivars with multiple R and QTL genes. To date, 展开更多
Genome dynamics of pathogenic organisms are driven by plant host and pathogenic organism co-evolution, in which patho- gen genomes areused to overcome stresses imposed by hosts with various genetic backgrounds through...Genome dynamics of pathogenic organisms are driven by plant host and pathogenic organism co-evolution, in which patho- gen genomes areused to overcome stresses imposed by hosts with various genetic backgrounds through generation of a range of field isolates. This model also applies to the rice host and its fungal pathogen Magnaporthe oryzae. To better understand genetic variation of M. oryzae in nature, the field isolate V86010 from the Philippines was sequenced and ana- lyzed. Genome annotation found that the assembled V86010 genome was composed of 1 931 scaffolds with a combined length of 38.9 Mb. The average GC ratio is 51.3% and repetitive elements constitute 5.1% of the genome. A total of 11 857 genes including 616 effector protein genes were predicted using a combined analysis pipeline. All predicted genes and effector protein genes of isolate V86010 distribute on the eight chromosomes when aligned with the assembled genome of isolate 70-15. Effector protein genes are located disproportionately at several chromosomal ends. The Pot2 elements are abundant in V86010. Seven V86010-specific effector proteins were found to suppress programmed cell death induced by BAX in tobacco leaves using an Agrobacterium-mediated transient assay. Our results may provide useful information for further study of the molecular and genomic dynamics in the evolution of M. oryzae and rice host interactions, and for characterizing novel effectors and AVR genes in the rice blast pathogen.展开更多
Knowledge of the geographic distribution and frequency of avirulence genes will contribute to the development of strategies to effectively use rice varieties that carry various resistances genes, including combination...Knowledge of the geographic distribution and frequency of avirulence genes will contribute to the development of strategies to effectively use rice varieties that carry various resistances genes, including combinations of varieties in mixture cropping systems. Here, we analyzed the geographic distribution and frequencies of avirulence genes in rice blast fungus using samples collected from 11 prefectures across Yunnan province, China. A total of 467 single spore isolates were assayed for pathotypes based on their reaction to 20 rice blast resistance monogenic lines. The results revealed that frequencies of avirulence genes among 10 prefectures showed insignificant difference, but frequencies of avirulenee genes in Xishuangbanna showed significant differences compared to the remaining 10 prefectures. The avirulence genes Avr-Pi9, Avr-Piz and Avr-Pizt were observed at the highest frequency in blast isolates from the 11 prefectures; their average frequency was greater than 80%. Our results imply that the composition and distribution of rice genetic diversity are more important than climate and other environment conditions for formation and maintenance of rice blast fungus genetic diversity. Using average frequencies, the avirulence genes can be categorized into 4 groups. There were significant differences of frequencies of avirulence genes among different groups, while insignificant differences observed within any group. These results will provide useful information for evaluation of resistance genes and effective management of rice blast disease.展开更多
基金support from the National Natural Science Foundation of China (U1405212)the National Key Research and Development Program of China (2016YFD0300707)+1 种基金the Natural Science Foundation of Fujian Province, China (2017J01618)the 100 Talent Project from Fujian Province to Dr.Daniel J.Ebbole (Texas A&M University, USA)
文摘Rice blast disease, caused by Magnaporthe oryzae, threatens global food security. The rice blast pathosystem is a longstanding model system for understanding plant-microbe interactions. In order to elucidate the coevolution of the host and pathogen, and provide the appropriate methods for preventing or controlling rice blast disease, researchers have focused on the evolution of virulence factors and resistance genes. Thus far, more than 30 rice blast resistance（R） genes and 12 avirulence（Avr） genes have been cloned. This review summarizes the cloned rice blast R genes, cloned Avr genes of M. oryzae and the interaction between them. This discussion also considers some of the major unanswered questions concerning this pathosystem and the opportunities for future investigations.
基金supported by the State Key Basic Research and Development Project of China (Grant No. 2006CB101902)the National Natural Science Foundation of China (Grant Nos. 30710103902 and 30671354)the Ministry of Agriculture of China (Grant No. NYHYZX07-056)
文摘Xanthomonas oryzae pv.oryzae,the causal agent of bacterial blight in rice,interacts with rice plants in a gene-for-gene manner.The specificity of the interaction is dictated by avirulence(avr) genes in the pathogen and resistance(R) genes in the host.To date,no avr genes that correspond to recessive R genes have been isolated.We isolated an avrBs3/pthA family gene,avrxa5,from our previously isolated clone p58,which was originally from strain JXOIII.The avrxa5 gene converted the PXO99A strain from compatible to incompatible in rice cultivars containing the recessive xa5 gene,but not in those containing the dominant Xa5 gene.Sequencing indicated that avrxa5,which is highly similar to members of the avrBs3/pthA family,encodes a protein of 1238 amino acid residues with a conserved carboxy-terminal region containing three nuclear localization signals and a transcription activation domain.It has 19.5 34-amino-acid direct repeats,but the 13th amino acid is missing in the fifth and ninth repetitive units.Domain swapping of the repetitive regions between avrxa5 and avrXa7 changed the avirulence specificity of the genes in xa5 and Xa7 rice lines,respectively.This indicates that avrxa5 is distinct from previously characterized avrBs3/pthA members.The specificity of avrxa5 toward recessive xa5 in rice could help us better understand the molecular mechanisms of plant-pathogen specific interactions.
基金supported by the National Natural Science Foundation of China(32171944 to Y.K.)the Chinese Academy of Agricultural Sciences under the Elite Youth program and the Agricultural Science and Technology Innovation Program+1 种基金Youth Innovation Program of Chinese Academy of Agricultural Sciences(Y2023QC22)the Key Projects of Zhejiang Provincial Natural Science Foundation(LZ23C130002).
文摘Rice blast,caused by Magnaporthe oryzae,is one of the most devastating diseases of rice.During infection,M.oryzae secretes effectors to facilitate blast development.Among these effectors,the avirulence factor AvrPi9 is recognized by Pi9,a broad-spectrum blast resistance protein that triggers Pi9-mediated resistance in rice.However,little is known about the interaction between AvrPi9 and Pi9 and how AvrPi9 exerts virulence to promote infection.In this study,we found that ectopic expression of AvrPi9 in the Pi9-lacking cultivar TP309 suppressed basal resistance against M.oryzae.Furthermore,we identified an AvrPi9-interacting protein in rice,which we named OsRGLG5,encoding a functional RING-type E3 ubiquitin ligase.During infection,AvrPi9 was ubiquitinated and degraded by OsRGLG5.Meanwhile,AvrPi9 affected the stability of OsRGLG5.Infection assays revealed that OsRGLG5 is a positive regulator of basal resistance against M.oryzae,but it is not essential for Pi9-mediated blast resistance in rice.In conclusion,our results revealed that OsRGLG5 is targeted by the M.oryzae effector AvrPi9 and positively regulates basal resistance against rice blast.
基金supported by grants from the National Natural Science Foundation of China(31401692,31901960,32272513,32001976)the Natural Science Foundation of Fujian Province(2019J01766,2023J011418,2020J05177)+3 种基金Fujian Provincial Science and Technology Key Project(2022NZ030014)External Cooperation Program of Fujian Academy of Agricultural Sciences(DWHZ-2024-23)State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crop Opening Project(SKL2019005)Project of Fujian Provincial Department of Education(JAT190627)。
文摘Avirulence effectors(Avrs),encoded by plant pathogens,can be recognized by plants harboring the corresponding resistance proteins,thereby initiating effector-triggered immunity(ETI).In susceptible plants,however,Avrs can function as effectors,facilitating infection via effector-triggered susceptibility(ETS).Mechanisms of Avr-mediated ETS remain largely unexplored.Here we report that the Magnaporthe oryzae effector Avr-PikD enters rice cells via the canonical cytoplasmic secretion pathway and suppresses rice basal defense.Avr-PikD interacts with an LSD1-like transcriptional activator AKIP30 of rice,and AKIP30 is also a positive regulator of rice immunity,whereas Avr-PikD impedes its nuclear localization and suppresses its transcriptional activity.In summary,M.oryzae delivers Avr-PikD into rice cells to facilitate ETS by inhibiting AKIP30-mediated transcriptional regulation of immune response against M.oryzae.
文摘The AVR-Pita1 gene,from the Chinese isolate O-137 of Magnaporthe oryzae,is an effector that determines the efficacy of the Pi-ta rice blast resistance gene.In the present study,the avirulence function of AVR-Pita1 was induced by transformation of field isolates(TM2,ZN19,B2 and B8)that originally were collected from the U.S.and are virulent on Pi-ta-carrying rice cultivars.The presence of AVR-Pita1 from O-137 in independent transformants was detected by PCR using AVR-Pita1 specific primers and verified by DNA sequencing and Southern blot analysis using the AVR-Pita1 coding region as a probe.The results of pathogenicity assays showed that the AVR-Pita1-transformed isolates were not able to infect rice cultivars Katy and Drew carrying Pi-ta.Control isolates that were transformed with inserts lacking the AVR-Pita1gene remained virulent.Our findings demonstrate that AVR-Pita1 can be used to induce novel gene-specific blast resistance in nature.
文摘Puccinia striiformis f. sp. tritici (Pst) is one of the pathogenic fungi on wheat, caused stripe rust that is a great threat for wheat production all over the world. Intensive efforts have been made to study genetics of wheat resistance to this disease, but few on avirulence of the pathogen due mainly to the nature of obligate biotrophism and the lack of systems for studying its genetics and molecular manipulations. To overcome these limitations, a natural Pst population comprising 352 isolates representative of a diverse virulence spectrum was genotyped using 97 secreted protein-single nucleotide polymorphism (SP-SNP) markers to identify candidate avirulence genes using association analysis. Among avirulence genes corresponding to 19 resistance genes, significantly associated SP-SNP markers were detected for avirulence genes AvYr1, AvYr2, AvYr6, AvYr7, AvYr8, AvYr44, AvYrExp2, AvYrSP, and AvYrTye. These results indicate that association analysis can be used to identify markers for avirulence genes. This study has laid the foundation for developing more SP-SNPs for mapping avirulence genes using segregating populations that can be generated through sexual reproduction on alternate hosts of the pathogen.
基金supported by the National Natural Science Foundation of China (31571993)the Natural Science Foundation of Liaoning Province of China (2014027027 and 2013020074)the Doctoral Fund of Liaoning Province of China (20131053)
文摘Understanding the sequence diversity of rice blast resistance genes is important for breeding new resistant rice cultivars against the rice blast fungusMagnaporthe oryzae. In this study, we selected 24 rice cultivars with different genetic back-grounds to study the alelic diversity of rice blast resistance genesPiz-t, Pitaand Pik. For Piz-t, a total of 17 alelic types were found within the 24 cultivars. Blast inoculations showed that most of the mutations can affect the function of the resistance gene. For Pita, except for the difference at the 918th amino acid, a majority of the 21 mutations were detected among the cultivars. Inoculations with blast isolates carryingAvr-Pita revealed that cultivars with mutations in other sites except for the 918th amino acid did not affect the function of thePita gene. ForPik, a total of six alelic types were found within the 24 cultivars, but ifve of them lost the function of the resistance gene. In addition, we found thatPiz-t, Pita and Pik were expressed constitutively in the 24 rice cultivars and the expression level was not related to resistance. Our results have provided the sequence diversity information of the resistance genesPiz-t, Pita and Pik among the popular rice cultivars grown in the northeast region of China. Keywords：resistance gene, avirulence gene, aleles, function, genetic evolution zae（M. oryzae）, is one of the most destructive diseases in rice production worldwide. Over the years, comprehensive studies on rice blast resistance have been conducted （Silue et al. 1992）. The resistance in newly cultivated rice cultivars to M. oryzae can be lost quickly due to the high level of instability in the genome of the fungus （Bonmanet al. 1992）. Previous studies show that cultivars with durable and broad-spectrum resistance againstM. oryzae carry multiple major resistance （R） and minor resistance genes （Liuet al. 2014）. An effective way to control rice blast disease is, therefore, to breed rice cultivars with multiple R and QTL genes. To date,
基金supported by the grants from the National Natural Science Foundation of China (31528017 and 31461143019)
文摘Genome dynamics of pathogenic organisms are driven by plant host and pathogenic organism co-evolution, in which patho- gen genomes areused to overcome stresses imposed by hosts with various genetic backgrounds through generation of a range of field isolates. This model also applies to the rice host and its fungal pathogen Magnaporthe oryzae. To better understand genetic variation of M. oryzae in nature, the field isolate V86010 from the Philippines was sequenced and ana- lyzed. Genome annotation found that the assembled V86010 genome was composed of 1 931 scaffolds with a combined length of 38.9 Mb. The average GC ratio is 51.3% and repetitive elements constitute 5.1% of the genome. A total of 11 857 genes including 616 effector protein genes were predicted using a combined analysis pipeline. All predicted genes and effector protein genes of isolate V86010 distribute on the eight chromosomes when aligned with the assembled genome of isolate 70-15. Effector protein genes are located disproportionately at several chromosomal ends. The Pot2 elements are abundant in V86010. Seven V86010-specific effector proteins were found to suppress programmed cell death induced by BAX in tobacco leaves using an Agrobacterium-mediated transient assay. Our results may provide useful information for further study of the molecular and genomic dynamics in the evolution of M. oryzae and rice host interactions, and for characterizing novel effectors and AVR genes in the rice blast pathogen.
基金supported by the National Natural Science Fund (30860161)National Basic Research Program (No. 2011CB100400)The Ministry of Science and Technology of China,the Natural Science Fund (2010ZC173)
文摘Knowledge of the geographic distribution and frequency of avirulence genes will contribute to the development of strategies to effectively use rice varieties that carry various resistances genes, including combinations of varieties in mixture cropping systems. Here, we analyzed the geographic distribution and frequencies of avirulence genes in rice blast fungus using samples collected from 11 prefectures across Yunnan province, China. A total of 467 single spore isolates were assayed for pathotypes based on their reaction to 20 rice blast resistance monogenic lines. The results revealed that frequencies of avirulence genes among 10 prefectures showed insignificant difference, but frequencies of avirulenee genes in Xishuangbanna showed significant differences compared to the remaining 10 prefectures. The avirulence genes Avr-Pi9, Avr-Piz and Avr-Pizt were observed at the highest frequency in blast isolates from the 11 prefectures; their average frequency was greater than 80%. Our results imply that the composition and distribution of rice genetic diversity are more important than climate and other environment conditions for formation and maintenance of rice blast fungus genetic diversity. Using average frequencies, the avirulence genes can be categorized into 4 groups. There were significant differences of frequencies of avirulence genes among different groups, while insignificant differences observed within any group. These results will provide useful information for evaluation of resistance genes and effective management of rice blast disease.
