The basidiomycetous fungus Sporisorium scitamineum causes sugarcane smut that leads to severe economic losses in the major sugarcane growing areas in China,India and Brazil,etc.Autophagy is a conserved pathway in euka...The basidiomycetous fungus Sporisorium scitamineum causes sugarcane smut that leads to severe economic losses in the major sugarcane growing areas in China,India and Brazil,etc.Autophagy is a conserved pathway in eukaryotes for bulk degradation and cellular recycling,and was shown to be important for fungal cell growth,development,and pathogenicity.However,physiological function of autophagy has not been studied in S.scitamineum.In this study,we identified a conserved Atg8 protein,named as SsAtg8 and characterized its function.Our results showed that autophagy was blocked in the ssatg8Δ mutant,in nitrogen starvation.The ssatg8Δ mutant formed pseudohypha frequently and was hypersensitive to oxidative stress.However,mating or filamenation was unaffected in the ssatg8Δ mutant in vitro.Overall we demonstrate that autophagy is dispensable for S.scitamineum mating/filamentation,while critical for oxidative stress tolerance and proper morphology in sporidial stage.展开更多
SnRK1,an evolutionarily conserved heterotrimeric kinase complex that acts as a key metabolic sensor in maintaining energy homeostasis in plants,is an important upstream activator of autophagy that serves as a cellular...SnRK1,an evolutionarily conserved heterotrimeric kinase complex that acts as a key metabolic sensor in maintaining energy homeostasis in plants,is an important upstream activator of autophagy that serves as a cellular degradation mechanism for the healthy growth of plants.However,whether and how the autophagy pathway is involved in regulating SnRK1 activity remains unknown.In this study,we identified a clade of plant-specific and mitochondria-localized Fcs-like zinc finger(FLZ)proteins as currently unknown ATG8-interacting partners that actively inhibit SnRK1 signaling by repressing the T-loop phosphorylation of the catalyticαsubunits of SnRK1,thereby negatively modulating autophagy and plant tolerance to energy deprivation caused by long-term carbon starvation.Interestingly,these AtFLZs are transcriptionally repressed by low-energy stress,and AtFLZ proteins undergo a selective autophagy-dependent pathway to be delivered to the vacuole for degradation,thereby constituting a positive feedback regulation to relieve their repression of SnRK1 signaling.Bioinformatic analyses show that the ATG8-FLZ-SnRK1 regulatory axis first appears in gymnosperms and seems to be highly conserved during the evolution of seed plants.Consistent with this,depletion of ATG8-interacting ZmFLZ14 confers enhanced tolerance,whereas overexpression of ZmFLZ14 leads to reduced tolerance to energy deprivation in maize.Collectively,our study reveals a previously unknown mechanism by which autophagy contributes to the positive feedback regulation of SnRK1 signaling,thereby enabling plants to better adapt to stressful environments.展开更多
Autophagy plays an important role in tissue remodeling during insect development.The interplay between autophagy-related(ATG)proteins and caspases regulates the autophagic activity of ATGs,thereby modulating the proce...Autophagy plays an important role in tissue remodeling during insect development.The interplay between autophagy-related(ATG)proteins and caspases regulates the autophagic activity of ATGs,thereby modulating the process of autophagy.Our previous study characterized BmCaspase-8-like(BmCasp8L)as a caspase suppressor that inhibits apoptosis and immune signaling by suppressing the activation of death-related ced-3/Nedd2-like caspase(DREDD),a caspase-8 homolog in silkworm.In this study,we explored the regulatory role of BmCasp8L in autophagy.We found that the expression of Bmcasp8l increased from the late spinning stage to the pupa stage in the posterior silk gland(PSG),correlating with the expression patterns of Bmatg8 and Bmatg6.RNA interference-mediated downregulation of BmCasp8L expression significantly decreased starvation-induced autophagic influx as determined by the levels of BmATG8–phosphatidylethanolamine and the percentage of cells displaying punctate enhanced green fluorescent protein-BmATG8.Conversely,the overexpression of BmCasp8L significantly increased autophagic influx.We also found that BmCasp8L underwent autophagic degradation induced by starvation and that it was colocalized with BmATG8.Lastly,we demonstrated that BmDREDD attenuated autophagy and BmCasp8L suppressed BmDREDD-mediated cleavage of BmATG6.Taken together,our results demonstrated that BmCasp8L is a novel proautophagic molecule which suppresses BmDREDD-mediated cleavage of BmATG6 and is a target for autophagy.展开更多
Extremely high or low autophagy levels disrupt plant survival under nutrient starvation.Recently,autophagy has been reported to display rhythms in animals.However,the mechanism of circadian regulation of autophagy is ...Extremely high or low autophagy levels disrupt plant survival under nutrient starvation.Recently,autophagy has been reported to display rhythms in animals.However,the mechanism of circadian regulation of autophagy is still unclear.Here,we observed that autophagy has a robust rhythm and that various autophagy-related genes(ATGs)are rhythmically expressed in Arabidopsis.Chromatin immunoprecipitation(Ch IP)and dual-luciferase(LUC)analyses showed that the core oscillator gene TIMING OF CAB EXPRESSION 1(TOC1)directly binds to the promoters of ATG(ATG1 a,ATG2,and ATG8 d)and negatively regulates autophagy activities under nutritional stress.Furthermore,autophagy defects might affect endogenous rhythms by reducing the rhythm amplitude of TOC1 and shortening the rhythm period of CIRCADIAN CLOCK-ASSOCIATED 1(CCA1).Autophagy is essential for the circadian clock pattern in seedling development and plant sensitivity to nutritional deficiencies.Taken together,our studies reveal a plant strategy in which the TOC1-ATG axis involved in autophagy-rhythm crosstalk to fine-tune the intensity of autophagy.展开更多
High temperature stress poses significant adverse effects on crop yield and quality.Yet the molecular mechanisms underlying heat stress tolerance in plants/crops,especially regarding the organellar remodeling and home...High temperature stress poses significant adverse effects on crop yield and quality.Yet the molecular mechanisms underlying heat stress tolerance in plants/crops,especially regarding the organellar remodeling and homeostasis,are largely unknown.In a recent study,Zhou et al.reported that autophagy-related 8(ATG8),a famous regulator involved in autophagy,plays a new role in Golgi restoration upon heat stress.Golgi apparatus is vacuolated following short-term acute heat stress,and ATG8 is translocated to the dilated Golgi membrane and interacts with CLATHRIN LIGHT CHAIN 2(CLC2)to facilitate Golgi restoration,which is dependent on the ATG conjugation system,but not of the upstream autophagic initiators.These exciting findings broaden the fundamental role of ATG8,and elucidate the organelle-level restoration mechanism of Golgi upon heat stress in plants.展开更多
Rice stripe virus(RSV)is the causative agent of rice stripe disease and is completely dependent on insect vectors for its plant-to-plant transmission.Laodelphax striatellus is the major insect vector for RSV.In this s...Rice stripe virus(RSV)is the causative agent of rice stripe disease and is completely dependent on insect vectors for its plant-to-plant transmission.Laodelphax striatellus is the major insect vector for RSV.In this study,we explored the interactions be-tween RSV infection and L.striatellus autophagy,a potential intrinsic antiviral mechanism in insects.We found that L.striatellus autophagic activity did not affect RSV infection;however,the autophagy related-8(Atg8)gene significantly enhanced virus infection.Dur-ing RSV initial infection within the L.striatellus midgut,silencing of Atg8 expression significantly decreased the phosphorylation of c-Jun N-terminal kinase(p-JNK);however,when RSV infection is absent,silencing of Atg8 did not alter p-JNK levels.Thesc results indicated that Atg8 might activate the JNK machinery by allowing more virus infection into cells.We further revealed that Atg8-deficiency significantly decreased RSV accumu-lation on the surface of the insect midgut epithelial cells,suggesting a receptor trafficking function of the y-aminobutyric acid receptor-associated protein family.Using the RSV ovary entry as a model,in which vitellogenin receptor(V gR)mediates RSV cell entry,we clarified that Atg8-deficiency decreased the abundance of V gR localizing on the cytomem-brane and disturbed the attachment of RSV in the germarium zones.Collectively,these results revealed an autophagy-independent function of L.striatellus Atg8 that enhances RSV initial infection by increasing virus attachment on the infection sites.展开更多
Autophagy is a conserved intracellular degradation process that plays an active role in plant response to virus infections.Here we report that geminiviruses counteract activated autophagymediated antiviral defense in ...Autophagy is a conserved intracellular degradation process that plays an active role in plant response to virus infections.Here we report that geminiviruses counteract activated autophagymediated antiviral defense in plant cells through the C2 proteins they encode.We found that,in Nicotiana benthamiana plants,tomato leaf curl Yunnan virus(TLCYnV)infection upregulated the transcription levels of autophagy-related genes(ATGs).Overexpression of NbATG5,NbATG7,or NbATG8a in N.benthamiana plants decreased TLCYnV accumulation and attenuated viral symptoms.Interestingly,transgenic overexpression of NbATG7 promoted the growth of N.benthamiana plants and enhanced plant resistance to TLCYnV.We further revealed that the C2 protein encoded by TLCYnV directly interacted with the ubiquitinactivating domain of ATG7.This interaction competitively disrupted the ATG7–ATG8 binding in N.benthamiana and Solanum lycopersicum plants,thereby inhibiting autophagy activity.Furthermore,we uncovered that the C2-mediated autophagy inhibition mechanism was conserved in three other geminiviruses.In summary,we discovered a novel counter-defensive strategy employed by geminiviruses that enlists their C2 proteins as disrupters of ATG7–ATG8 interactions to defeat antiviral autophagy.展开更多
基金supported by the National 973 Program of China(2015CB150600)the Natural Science Foundation of Guangdong Province,China(2017A030310144)
文摘The basidiomycetous fungus Sporisorium scitamineum causes sugarcane smut that leads to severe economic losses in the major sugarcane growing areas in China,India and Brazil,etc.Autophagy is a conserved pathway in eukaryotes for bulk degradation and cellular recycling,and was shown to be important for fungal cell growth,development,and pathogenicity.However,physiological function of autophagy has not been studied in S.scitamineum.In this study,we identified a conserved Atg8 protein,named as SsAtg8 and characterized its function.Our results showed that autophagy was blocked in the ssatg8Δ mutant,in nitrogen starvation.The ssatg8Δ mutant formed pseudohypha frequently and was hypersensitive to oxidative stress.However,mating or filamenation was unaffected in the ssatg8Δ mutant in vitro.Overall we demonstrate that autophagy is dispensable for S.scitamineum mating/filamentation,while critical for oxidative stress tolerance and proper morphology in sporidial stage.
基金grants from the National Natural Science Foundation of China(32061160467,32270291,31870171)Open Competition Program of Top Ten Critical Priorities of Agricultural Science and Technology Innovation for the 14th Five-Year Plan of Guangdong Province(2022SDZG05)to C.G+6 种基金the Youth Innovation Promotion Association,Chinese Academy of Sciences(2023364)the Guangdong Basic and Applied Basic Research Foundation(2022A1515012319)the Guangzhou Basic and Applied Basic Research Foundation(2023A04J0094)to C.Y.the National Natural Science Foundation of China(32222087)the Research Grants Council of Hong Kong(N_CUHK405/20,24108820,and 14106622)The Chinese University of Hong Kong(CUHK)Research Committee to X.Z.the US National Science Foundation(#MCB-2040582)to D.C.B.
文摘SnRK1,an evolutionarily conserved heterotrimeric kinase complex that acts as a key metabolic sensor in maintaining energy homeostasis in plants,is an important upstream activator of autophagy that serves as a cellular degradation mechanism for the healthy growth of plants.However,whether and how the autophagy pathway is involved in regulating SnRK1 activity remains unknown.In this study,we identified a clade of plant-specific and mitochondria-localized Fcs-like zinc finger(FLZ)proteins as currently unknown ATG8-interacting partners that actively inhibit SnRK1 signaling by repressing the T-loop phosphorylation of the catalyticαsubunits of SnRK1,thereby negatively modulating autophagy and plant tolerance to energy deprivation caused by long-term carbon starvation.Interestingly,these AtFLZs are transcriptionally repressed by low-energy stress,and AtFLZ proteins undergo a selective autophagy-dependent pathway to be delivered to the vacuole for degradation,thereby constituting a positive feedback regulation to relieve their repression of SnRK1 signaling.Bioinformatic analyses show that the ATG8-FLZ-SnRK1 regulatory axis first appears in gymnosperms and seems to be highly conserved during the evolution of seed plants.Consistent with this,depletion of ATG8-interacting ZmFLZ14 confers enhanced tolerance,whereas overexpression of ZmFLZ14 leads to reduced tolerance to energy deprivation in maize.Collectively,our study reveals a previously unknown mechanism by which autophagy contributes to the positive feedback regulation of SnRK1 signaling,thereby enabling plants to better adapt to stressful environments.
基金supported by grants from the National Natural Science Foundation of China(No.31672495)Natural Science Foundation of Chongqing,China(cstc2020jcyj-msxmX0193).
文摘Autophagy plays an important role in tissue remodeling during insect development.The interplay between autophagy-related(ATG)proteins and caspases regulates the autophagic activity of ATGs,thereby modulating the process of autophagy.Our previous study characterized BmCaspase-8-like(BmCasp8L)as a caspase suppressor that inhibits apoptosis and immune signaling by suppressing the activation of death-related ced-3/Nedd2-like caspase(DREDD),a caspase-8 homolog in silkworm.In this study,we explored the regulatory role of BmCasp8L in autophagy.We found that the expression of Bmcasp8l increased from the late spinning stage to the pupa stage in the posterior silk gland(PSG),correlating with the expression patterns of Bmatg8 and Bmatg6.RNA interference-mediated downregulation of BmCasp8L expression significantly decreased starvation-induced autophagic influx as determined by the levels of BmATG8–phosphatidylethanolamine and the percentage of cells displaying punctate enhanced green fluorescent protein-BmATG8.Conversely,the overexpression of BmCasp8L significantly increased autophagic influx.We also found that BmCasp8L underwent autophagic degradation induced by starvation and that it was colocalized with BmATG8.Lastly,we demonstrated that BmDREDD attenuated autophagy and BmCasp8L suppressed BmDREDD-mediated cleavage of BmATG6.Taken together,our results demonstrated that BmCasp8L is a novel proautophagic molecule which suppresses BmDREDD-mediated cleavage of BmATG6 and is a target for autophagy.
基金supported by grants from the National Natural Science Foundation of China(NSFC–31871396,31571444)the Young Elite Scientist Sponsorship Program of CAST(YESS20160001)+3 种基金the Open Research Fund of the State Key Laboratory of Hybrid Rice(Hunan Hybrid Rice Research Center)to Feng Yuthe Foundation of Hunan Provincial Natural Science(2021JJ30540)the Foundation of Hunan Double First-rate Discipline Construction Projects of Bioengineering to Zhaotun Huthe China Tobacco Hunan Industrial Co.,Ltd.Research Project(KY2021YC0001)to W.X.P。
文摘Extremely high or low autophagy levels disrupt plant survival under nutrient starvation.Recently,autophagy has been reported to display rhythms in animals.However,the mechanism of circadian regulation of autophagy is still unclear.Here,we observed that autophagy has a robust rhythm and that various autophagy-related genes(ATGs)are rhythmically expressed in Arabidopsis.Chromatin immunoprecipitation(Ch IP)and dual-luciferase(LUC)analyses showed that the core oscillator gene TIMING OF CAB EXPRESSION 1(TOC1)directly binds to the promoters of ATG(ATG1 a,ATG2,and ATG8 d)and negatively regulates autophagy activities under nutritional stress.Furthermore,autophagy defects might affect endogenous rhythms by reducing the rhythm amplitude of TOC1 and shortening the rhythm period of CIRCADIAN CLOCK-ASSOCIATED 1(CCA1).Autophagy is essential for the circadian clock pattern in seedling development and plant sensitivity to nutritional deficiencies.Taken together,our studies reveal a plant strategy in which the TOC1-ATG axis involved in autophagy-rhythm crosstalk to fine-tune the intensity of autophagy.
基金financially supported by grants from the State Key Project of Research and Development Plan(2021YFF1000404,2022YFF1001603).
文摘High temperature stress poses significant adverse effects on crop yield and quality.Yet the molecular mechanisms underlying heat stress tolerance in plants/crops,especially regarding the organellar remodeling and homeostasis,are largely unknown.In a recent study,Zhou et al.reported that autophagy-related 8(ATG8),a famous regulator involved in autophagy,plays a new role in Golgi restoration upon heat stress.Golgi apparatus is vacuolated following short-term acute heat stress,and ATG8 is translocated to the dilated Golgi membrane and interacts with CLATHRIN LIGHT CHAIN 2(CLC2)to facilitate Golgi restoration,which is dependent on the ATG conjugation system,but not of the upstream autophagic initiators.These exciting findings broaden the fundamental role of ATG8,and elucidate the organelle-level restoration mechanism of Golgi upon heat stress in plants.
文摘Rice stripe virus(RSV)is the causative agent of rice stripe disease and is completely dependent on insect vectors for its plant-to-plant transmission.Laodelphax striatellus is the major insect vector for RSV.In this study,we explored the interactions be-tween RSV infection and L.striatellus autophagy,a potential intrinsic antiviral mechanism in insects.We found that L.striatellus autophagic activity did not affect RSV infection;however,the autophagy related-8(Atg8)gene significantly enhanced virus infection.Dur-ing RSV initial infection within the L.striatellus midgut,silencing of Atg8 expression significantly decreased the phosphorylation of c-Jun N-terminal kinase(p-JNK);however,when RSV infection is absent,silencing of Atg8 did not alter p-JNK levels.Thesc results indicated that Atg8 might activate the JNK machinery by allowing more virus infection into cells.We further revealed that Atg8-deficiency significantly decreased RSV accumu-lation on the surface of the insect midgut epithelial cells,suggesting a receptor trafficking function of the y-aminobutyric acid receptor-associated protein family.Using the RSV ovary entry as a model,in which vitellogenin receptor(V gR)mediates RSV cell entry,we clarified that Atg8-deficiency decreased the abundance of V gR localizing on the cytomem-brane and disturbed the attachment of RSV in the germarium zones.Collectively,these results revealed an autophagy-independent function of L.striatellus Atg8 that enhances RSV initial infection by increasing virus attachment on the infection sites.
基金support from the National Natural Science Foundation of China(31930089)to X.Z.the National Key Research and Development Program of China(2021YFD1400400)to F.L.
文摘Autophagy is a conserved intracellular degradation process that plays an active role in plant response to virus infections.Here we report that geminiviruses counteract activated autophagymediated antiviral defense in plant cells through the C2 proteins they encode.We found that,in Nicotiana benthamiana plants,tomato leaf curl Yunnan virus(TLCYnV)infection upregulated the transcription levels of autophagy-related genes(ATGs).Overexpression of NbATG5,NbATG7,or NbATG8a in N.benthamiana plants decreased TLCYnV accumulation and attenuated viral symptoms.Interestingly,transgenic overexpression of NbATG7 promoted the growth of N.benthamiana plants and enhanced plant resistance to TLCYnV.We further revealed that the C2 protein encoded by TLCYnV directly interacted with the ubiquitinactivating domain of ATG7.This interaction competitively disrupted the ATG7–ATG8 binding in N.benthamiana and Solanum lycopersicum plants,thereby inhibiting autophagy activity.Furthermore,we uncovered that the C2-mediated autophagy inhibition mechanism was conserved in three other geminiviruses.In summary,we discovered a novel counter-defensive strategy employed by geminiviruses that enlists their C2 proteins as disrupters of ATG7–ATG8 interactions to defeat antiviral autophagy.
