23 research outputs found
Xylella fastidiosa : An in vivo system to study possible survival strategies within citrus xylem vessels based on global gene expression analysis
Abstract Xylella fastidiosa inhabits the plant xylem, a nutrient-poor
environment, so that mechanisms to sense and respond to adverse
environmental conditions are extremely important for bacterial survival
in the plant host. Although the complete genome sequences of different
Xylella strains have been determined, little is known about stress
responses and gene regulation in these organisms. In this work, a DNA
microarray was constructed containing 2,600 ORFs identified in the
genome sequencing project of Xylella fastidiosa 9a5c strain, and used
to check global gene expression differences in the bacteria when it is
infecting a symptomatic and a tolerant citrus tree. Different patterns
of expression were found in each variety, suggesting that bacteria are
responding differentially according to each plant xylem environment.
The global gene expression profile was determined and several genes
related to bacterial survival in stressed conditions were found to be
differentially expressed between varieties, suggesting the involvement
of different strategies for adaptation to the environment. The
expression pattern of some genes related to the heat shock response,
toxin and detoxification processes, adaptation to atypical conditions,
repair systems as well as some regulatory genes are discussed in this
paper. DNA microarray proved to be a powerful technique for global
transcriptome analyses. This is one of the first studies of Xylella
fastidiosa gene expression in vivo which helped to increase insight
into stress responses and possible bacterial survival mechanisms in the
nutrient-poor environment of xylem vessels
Field performance of "marsh seedless" grapefruit on trifoliate orange inoculated with viroids in Brazil
Viroid species associated with the bark-cracking phenotype of `Tahiti` acid lime in the State of Sao Paulo, Brazil
Viroids have been used as ""graft transmissible dwarfing agents"" (GTDA) in several countries, mainly to reduce growth of citrus trees, thus increasing their density in orchards. In the State of Sao Paulo, Brazil, plants of the acid lime `Tahiti` are usually grafted with a complex of GTDA, presumably viroids. The aim of the present work was the identification and molecular characterization of the viroids infecting trees of acid lime `Tahiti` displaying ""Quebra galho"" (bark-cracking). Viroids were identified and characterized by biological indexing in `Etrog` citron, Northern-blot hybridization, RT-PCR, cloning and complete sequencing of the RNA genomes. Citrus exocortis viroid (CEVd), Hop stunt viroid (HSVd) and Citrus dwarfing viroid (CDVd) were found in different combinations. Although we have not been able to infer a direct relationship between the agronomical performance and symptom severity with the presence of a specific viroid or viroid combination, the differences in the severity of ""Quebra-galho"" symptoms among different trees is probably associated with the presence (or absence) of CEVd, with its interaction with other viroids perhaps determining the different phenotypes observed in the field.Conselho Nacional de Desenvolvimento Cientifico e Tecnologico - CNPq[474522/2007-5]Fundacion Carolina (Madrid, Spain)Ministerio de Educacion y Ciencia (Spain)[AGL2007-65653-C02-01]Ministerio de Ciencia e Innovacion (MICINN, Spain)[BIO2008-01986]MICINN[BFU2008-03154/BMC]Generalitat Valenciana (Spain)[ACOMP/2010/278
Xylella fastidiosa: An in vivo system to study possible survival strategies within citrus xylem vessels based on global gene expression analysis
Xylella fastidiosa inhabits the plant xylem, a nutrient-poor environment, so that mechanisms to sense and respond to adverse environmental conditions are extremely important for bacterial survival in the plant host. Although the complete genome sequences of different Xylella strains have been determined, little is known about stress responses and gene regulation in these organisms. In this work, a DNA microarray was constructed containing 2,600 ORFs identified in the genome sequencing project of Xylella fastidiosa 9a5c strain, and used to check global gene expression differences in the bacteria when it is infecting a symptomatic and a tolerant citrus tree. Different patterns of expression were found in each variety, suggesting that bacteria are responding differentially according to each plant xylem environment. The global gene expression profile was determined and several genes related to bacterial survival in stressed conditions were found to be differentially expressed between varieties, suggesting the involvement of different strategies for adaptation to the environment. The expression pattern of some genes related to the heat shock response, toxin and detoxification processes, adaptation to atypical conditions, repair systems as well as some regulatory genes are discussed in this paper. DNA microarray proved to be a powerful technique for global transcriptome analyses. This is one of the first studies of Xylella fastidiosa gene expression in vivo which helped to increase insight into stress responses and possible bacterial survival mechanisms in the nutrient-poor environment of xylem vessels.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES