After its maturity,El Niño usually decays rapidly in the following summer and evolves into a La Niña pattern.However,this was not the case for the 2018/19 El Niño event.Based on multiple reanalysis data...After its maturity,El Niño usually decays rapidly in the following summer and evolves into a La Niña pattern.However,this was not the case for the 2018/19 El Niño event.Based on multiple reanalysis data sets,the space-time evolution and triggering mechanism for the unusual second-year warming in late 2019,after the 2018/19 El Niño event,are investigated in the tropical Pacific.After a short decaying period associated with the 2018/19 El Niño condition,positive sea surface temperature anomalies(SSTAs)re-intensified in the eastern equatorial Pacific in late 2019.Compared with the composite pattern of El Niño in the following year,two key differences are evident in the evolution of SSTAs in 2019.First,is the persistence of the surface warming over the central equatorial Pacific in May,and second,is the re-intensification of the positive SSTAs over the eastern equatorial Pacific in September.Observational results suggest that the re-intensification of anomalous westerly winds over the western and central Pacific,induced remotely by an extreme Indian Ocean Dipole(IOD)event,acted as a triggering mechanism for the second-year warming in late 2019.That is,the IOD-related cold SSTAs in the eastern Indian Ocean established and sustained anomalous surface westerly winds over the western equatorial Pacific,which induced downwelling Kelvin waves propagating eastward along the equator.At the same time,the subsurface ocean provided plenty of warm water in the western and central equatorial Pacific.Mixed-layer heat budget analyses further confirm that positive zonal advection,induced by the anomalous westerly winds,and thermocline feedback played important roles in leading to the second-year warming in late 2019.This study provides new insights into the processes responsible for the diversity of El Niño evolution,which is important for improving the physical understanding and seasonal prediction of El Niño events.展开更多
Salicylic acid(SA)is an important plant hormone that regulates defense responses and leaf senescence.It is imperative to understand upstream factors that regulate genes of SA biosynthesis.SAG202/SARD1 is a key regulat...Salicylic acid(SA)is an important plant hormone that regulates defense responses and leaf senescence.It is imperative to understand upstream factors that regulate genes of SA biosynthesis.SAG202/SARD1 is a key regulator for isochorismate synthase 1(ICS1)induction and SA biosynthesis in defense responses.The regulatory mechanism of SA biosynthesis during leaf senescence is not well understood.Here we show that AtNAP,a senescence-specific NAC family transcription factor,directly regulates a senescence-associated gene named SAG202 as revealed in yeast one-hybrid and in planta assays.Inducible overexpreesion of AtNAP and SAG202 lead to high levels of SA and precocious senescence in leaves.Individual knockout mutants of sag202 and ics1 have markedly reduced SA levels and display a significantly delayed leaf senescence phenotype.Furthermore,SA positively feedback regulates AtNAP and SAG202.Our research has uncovered a unique positive feedback regulatory loop,SA-AtNAP-SAG202-ICS1-SA,that operates to control SA biosynthesis associated with leaf senescence but not defense response.展开更多
基金This work is jointly supported by grants from the National Key Research and Development Program(Grant No.2018YFC1505802)the National Natural Science Foundation of China(Grant Nos.41576029,42030410,41690122(41690120),41420104002)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant Nos.XDA19060102,XDB 40000000 and XDB 42000000).
文摘After its maturity,El Niño usually decays rapidly in the following summer and evolves into a La Niña pattern.However,this was not the case for the 2018/19 El Niño event.Based on multiple reanalysis data sets,the space-time evolution and triggering mechanism for the unusual second-year warming in late 2019,after the 2018/19 El Niño event,are investigated in the tropical Pacific.After a short decaying period associated with the 2018/19 El Niño condition,positive sea surface temperature anomalies(SSTAs)re-intensified in the eastern equatorial Pacific in late 2019.Compared with the composite pattern of El Niño in the following year,two key differences are evident in the evolution of SSTAs in 2019.First,is the persistence of the surface warming over the central equatorial Pacific in May,and second,is the re-intensification of the positive SSTAs over the eastern equatorial Pacific in September.Observational results suggest that the re-intensification of anomalous westerly winds over the western and central Pacific,induced remotely by an extreme Indian Ocean Dipole(IOD)event,acted as a triggering mechanism for the second-year warming in late 2019.That is,the IOD-related cold SSTAs in the eastern Indian Ocean established and sustained anomalous surface westerly winds over the western equatorial Pacific,which induced downwelling Kelvin waves propagating eastward along the equator.At the same time,the subsurface ocean provided plenty of warm water in the western and central equatorial Pacific.Mixed-layer heat budget analyses further confirm that positive zonal advection,induced by the anomalous westerly winds,and thermocline feedback played important roles in leading to the second-year warming in late 2019.This study provides new insights into the processes responsible for the diversity of El Niño evolution,which is important for improving the physical understanding and seasonal prediction of El Niño events.
基金This research was supported by National Science Foundation(NSF)Grant MCB-0445596,Department of Energy(DOE)Grant DE-FG02-02ER15341 and Cornell University(to S.G.).Both B.L.and Y.H.were funded by scholarships from China Scholars Council.
文摘Salicylic acid(SA)is an important plant hormone that regulates defense responses and leaf senescence.It is imperative to understand upstream factors that regulate genes of SA biosynthesis.SAG202/SARD1 is a key regulator for isochorismate synthase 1(ICS1)induction and SA biosynthesis in defense responses.The regulatory mechanism of SA biosynthesis during leaf senescence is not well understood.Here we show that AtNAP,a senescence-specific NAC family transcription factor,directly regulates a senescence-associated gene named SAG202 as revealed in yeast one-hybrid and in planta assays.Inducible overexpreesion of AtNAP and SAG202 lead to high levels of SA and precocious senescence in leaves.Individual knockout mutants of sag202 and ics1 have markedly reduced SA levels and display a significantly delayed leaf senescence phenotype.Furthermore,SA positively feedback regulates AtNAP and SAG202.Our research has uncovered a unique positive feedback regulatory loop,SA-AtNAP-SAG202-ICS1-SA,that operates to control SA biosynthesis associated with leaf senescence but not defense response.
