The structural basis for activation of plant immunity by bacterial effector protein AvrPto

Pathogenic microbes use effectors to enhance susceptibility in host plants. However, plants have evolved a sophisticated immune system to detect these effectors using cognate disease resistance proteins, a recognition that is highly specific, often elicits rapid and localized cell death, known as a hypersensitive response, and thus potentially limits pathogen growth. Despite numerous genetic and biochemical studies on the interactions between pathogen effector proteins and plant resistance proteins, the structural bases for such interactions remain elusive. The direct interaction between the tomato protein kinase Pto and the Pseudomonas syringae effector protein AvrPto is known to trigger disease resistance and programmed cell death through the nucleotide-binding site/leucine-rich repeat (NBS-LRR) class of disease resistance protein Prf. Here we present the crystal structure of an AvrPto-Pto complex. Contrary to the widely held hypothesis that AvrPto activates Pto kinase activity, our structural and biochemical analyses demonstrated that AvrPto is an inhibitor of Pto kinase in vitro. The AvrPto-Pto interaction is mediated by the phosphorylation-stabilized P+1 loop and a second loop in Pto, both of which negatively regulate the Prf-mediated defences in the absence of AvrPto in tomato plants. Together, our results show that AvrPto derepresses host defences by interacting with the two defence-inhibition loops of Pto.     

Fine mapping of the rice bacterial blight resistance gene Xa-4 and its co-segregation marker

An F₂ population developed from theXa-4 near isogenic lines, IR24 and IRBB4, was used for fine mapping of the rice bacterial blight resistance gene,Xa-4. Some restriction fragment length polymorphism (RFLP) markers on the high-density map constructed by Harushima et al. and the amplified DNA fragments homologous to the conserved domains of plant disease resistance (R) genes were used to construct the genetic linkage map around the geneXa-4 by scoring susceptible individuals in the population.Xa-4 was mapped between the RFLP marker G181 and the polymerase chain reaction (PCR) marker M55. The R gene homologous fragment marker RS13 was found co-segregating withXa-4 by analyzing all the plants in the population. This result opened an approach to map-based cloning of this gene, and marker RS13 can be applied to molecular marker-assisted selection ofXa-4 in rice breeding programs.     

水稻分子连锁图谱及重要性状的基因定位

对窄叶青８号京系１７的Ｆ１进行花药培养,获得了含有１３２个株系的加倍单倍体群体。     

Extension of the rice DH population genetic map with microsatellite markers

Genetic mapping of microsatellite markers was carried out in a rice DH population derived from across between Zaiyeqing 8 (indica) and Jingxi 17 (japonica). A total of 89 microsatellite markers, including 84 (GA)_n, 2(TCT)_n, 2(ATT)_n, and, l(ATC)_n motifs, were integrated relatively evenly into the established genetic map of the DH population. This will facilitate the utilization of microsatillite markers in rice gene mapping and marker aided breeding.     

Identification of salt-tolerance QTL in rice (Oryza sativa L.)

Quantitative trait loci (QTLs) controlling salt-tolerance at the seedling stage in rice (Oryza sativa L.) were identified by interval mapping (SIM) and composite interval mapping (CIM) using a doubled haploid population ZJDH and its high resolution genetic linkage map. The population was derived from an inter-subspecific cross between an indica variety Zhaiyeqing8 (ZYQ8) and a japonica variety Jingxi17 (JX17). Analysis of survival days of seedlings treated with 0.7% NaCI revealed that a major salt-tolerance quantitative trait locus (QTL), Std, was present between markers RG612 and C131 on chromosome 1 when using both MAPMAKER/QTL 1.1 and PLABQTL 1.0 (SIM). Its allele which contributes to salt-tolerance was from ZYQ8. In addition, seven more QTLs which give additive effect on salt-tolerance are identified when using PLABQTL (CIM), and most of them were from JX17.     

才子佳人戏曲中婚姻爱情受阻原因浅析

文章从才子佳人戏曲中婚姻爱情受阻原因入手,从主客观原因两方面来论说．希望能从中得到启示。