CandidatusLiberibacter americanus induces significant reprogramming of the transcriptome of the susceptible citrus genotype

Abstract

BackgroundCitrus huanglongbing (HLB) disease is caused by endogenous, phloem-restricted, Gram negative, uncultured bacteria named Candidatus Liberibacter africanus (CaLaf), Ca. L. asiaticus (CaLas), and Ca. L. americanus (CaLam), depending on the continent where the bacteria were first detected. The Asian citrus psyllid vector, Diaphorina citri, transmits CaLas and CaLam and both Liberibacter species are present in Brazil. Several studies of the transcriptional response of citrus plants manifesting HLB symptoms have been reported, but only for CaLas infection. This study evaluated the transcriptional reprogramming of a susceptible genotype of sweet orange challenged with CaLam, using a customized 385K microarray containing approximately 32,000 unigene transcripts. We analyzed global changes in gene expression of CaLam-infected leaves of sweet orange during the symptomatic stage of infection and compared the results with previously published microarray studies that used CaLas-infected plants. Twenty candidate genes were selected to validate the expression profiles in symptomatic and asymptomatic PCR-positive leaves infected with CaLas or CaLam.ResultsThe microarray analysis identified 633 differentially expressed genes during the symptomatic stage of CaLam infection. Among them, 418 (66%) were upregulated and 215 (34%) were down regulated. Five hundred and fourteen genes (81%) were orthologs of genes from Arabidopsis thaliana. Gene set enrichment analysis (GSEA) revealed that several of the transcripts encoded transporters associated with the endomembrane system, especially zinc transport. Among the most biologically relevant gene transcripts in GSEA were those related to signaling, metabolism and/or stimulus to hormones, genes responding to stress and pathogenesis, biosynthesis of secondary metabolites, oxidative stress and transcription factors belonging to different families. Real time PCR of 20 candidate genes validated the expression pattern of some genes in symptomatic and asymptomatic leaves infected with CaLam or CaLas.ConclusionsMany gene transcripts and biological processes are significantly altered upon CaLam infection. Some of them had been identified in response to CaLas infection, while others had not been previously reported. These data will be useful for selecting target genes for genetic engineering to control HLB.

Efecto del HLB sobre el rendimiento de limón mexicano en Colima, México

“…Moreover, studies at the genomic level have been ascertained that HLB can alter the expression of a large number of genes in various organs of infected plants (Kim et al, 2009;Liao and Burns, 2012;Mafra et al, 2013;Zheng and Zhao, 2013;Aritua et al, 2013;Zhong et al, 2015;Wang et al, 2016). Some genes are overexpressed, but others reduce its expression.…”

Enhancing and initiating phage-based therapies

“…The superbug phenomenon may already be approaching this level in the area of citrus trees, as illustrated by the following quotes from the popular press concerning citrus greening disease (a disease caused by Candidatus Liberibacter americanus): 27 "If we don't find a cure soon, we won't be growing oranges in Florida much longer." "The future of the citrus industry is at stake."…”

Expressão do gene <i>uid</i>A sob controle de promotores preferencialmente expressos no floema de plantas transgênicas de citrange \'Carrizo\'

“…A introdução desse vírus nas lavouras brasileiras aniquilou a citricultura da época, que se ergueu somente após a substituição da laranja Azeda pelo limão 'Cravo' (C. limonia Osbeck), como porta enxerto tolerante ao CTV (FEICHTENBERGER et al, 2005;MATTOS JUNIOR et al, 2005 CLam, que inicialmente era prevalente no campo, praticamente não é mais encontrada nos pomares, tendo sido substituída por CLas, que é a principal espécie causadora do HLB em todo o mundo (LOPES et al, 2009;ISLAM et al, 2012). Analisando-se as modificações de atividade do hospedeiro durante a resposta de obstrução do fluxo de fotoassimilados, podem-se obter informações importantes sobre os mecanismos da interação patógeno-hospedeiro que podem levar ao desenvolvimento de novas estratégias de proteção de plantas (ALBRECHT e BOWMAN, 2012;MAFRA et al, 2013;DALIO et al, 2017). Paralelamente ao modo de ação das bactérias na planta, esse conhecimento pode auxiliar as bases de pesquisa para o desenvolvimento de cultivares resistentes à doença com o uso de técnicas de biologia molecular para superar dificuldades do melhoramento convencional (GROSSER; GMITTER JUNIOR, 1990;CERVERA et al, 2009;DUTT et al, 2015).…”