Huanglongbing (HLB) is a vascular disease of Citrus caused by three species of the α-proteobacteria “Candidatus Liberibacter”, with “Candidatus Liberibacter asiaticus” (CLas) being the most widespread and the one causing significant economic losses in citrus-producing regions worldwide. However, Persian lime (Citrus latifolia Tanaka) has shown tolerance to the disease. To understand the molecular mechanisms of this tolerance, transcriptomic analysis of HLB was performed using asymptomatic and symptomatic leaves. RNA-Seq analysis revealed 652 differentially expressed genes (DEGs) in response to CLas infection, of which 457 were upregulated and 195 were downregulated. KEGG analysis revealed that after CLas infection, some DEGs were present in the plant–pathogen interaction and in the starch and sucrose metabolism pathways. DEGs present in the plant–pathogen interaction pathway suggests that tolerance against HLB in Persian lime could be mediated, at least partly, by the ClRSP2 and ClHSP90 genes. Previous reports documented that RSP2 and HSP90 showed low expression in susceptible citrus genotypes. Regarding the starch and sucrose metabolism pathways, some genes were identified as being related to the imbalance of starch accumulation. On the other hand, eight biotic stress-related genes were selected for further RT-qPCR analysis to validate our results. RT-qPCR results confirmed that symptomatic HLB leaves had high relative expression levels of the ClPR1, ClNFP, ClDR27, and ClSRK genes, whereas the ClHSL1, ClRPP13, ClPDR1, and ClNAC genes were expressed at lower levels than those from HLB asymptomatic leaves. Taken together, the present transcriptomic analysis contributes to the understanding of the CLas-Persian lime interaction in its natural environment and may set the basis for developing strategies for the integrated management of this important Citrus disease through the identification of blanks for genetic improvement.
El objetivo fue evaluar el modelo conceptual de fertilización para generar dosis nitrogenadas en maíz en la Costa del Golfo de México. Este consistió en el balance entre demanda de nitrógeno del cultivo, menos el suministro de nitrógeno por el suelo entre la eficiencia del fertilizante en cuatro tratamientos (VS-536 y V-537 C con y sin fertilizante). Los parámetros fisiotécnicos evaluados en las localidades Jamapa, Paso Real y El Rincón, del municipio de Jamapa, Veracruz fueron: demanda del cultivo, suministro de nutrimentos por el suelo y eficiencia del fertilizante. La demanda de nitrógeno con fertilizante fue estadísticamente superior a la no fertilizada; el suministro en ambos tratamientos fue estadísticamente similar. La eficiencia del fertilizante nitrogenado fue menor al 50% en las tres localidades. Las dosis de nitrógeno estimadas con el modelo conceptual fueron diferentes en las tres localidades (Jamapa 85, Rincón 55, y Paso Real, 72 kg N ha-1) en comparación con la dosis aplicada (150 kg N ha-1), lo que representa una sobrefertilización del 44%, 64% y 52% para Jamapa, Rincón y Paso Real. Se concluye que este modelo permitió generar dosis adecuadas de Nitrógeno en menor tiempo y con una menor inversión.
Huanglongbing (HLB) or citrus greening is currently the most important citrus disease, caused by the bacterium Candidatus Liberibacter asiaticus (CLas). The impossibility of isolating it causes understanding its pathogenic mechanisms to be a complicated task. Recent studies identified 16 proteins with the signal peptide needed to be secreted in the plant and cause the disease. The present study aims to perform a bioinformatic analysis of these proteins with the function prediction approach by gene ontology (GO) and the detection of conserved domains. It was observed that of the 16 proteins analyzed not all are found in different infective strains reported in the literature. The GO analysis allowed us to relate different proteins with the biological process of energy and pathogenic activity, especially CLIBASIA_03315 and CLIBASIA_05115, respectively. The domain analysis allowed the observation of a β-CA domain, tentatively related to the damage caused to the chloroplast and a PAAR domain associated with the T6SS secretory system. Our results provide information on the possible function of potential pathogenicity effectors in CLas.
Persian lime (PL) is one of the most economically important citrus crops in the state of Veracruz, Mexico. However, it is affected by the presence of Huanglongbing (HLB) disease, caused by Candidatus Liberibacter asiaticus (CLas), an obligate biotrophic pathogen. Overall, PL shows a certain level of tolerance to HLB. Therefore, it is important to study the defense response mediated by salicylic acid (SA) against biotrophic pathogens in PL. Some genes with the capacity to participate in the SA response pathway, known as NtSABP, have been identified in Nicotiana tabacum, but the presence and activity of these genes in PL in response to HLB are unknown. The objective of this study was to identify homologues of SABP-like proteins in the PL transcriptome and to determine their differential expression level during CLas infection. SABP protein sequences from five different species, including N. tabacum, were used as model sequences in a tBLASTn search. A 3D model of the SABP protein was constructed and compared between N. tabacum and C. latifolia. We identified the direct homologous to each NtSABP gene in the PL using tBLASTn analysis, phylogenetic reconstruction, and tridimensional structure. Interestingly, the ClSABP1, ClSABP2, and ClSABP3 genes showed repression in CLas infected plants. There is at least one homologous to each NtSABP gene in PL. During CLas infection, these genes are somewhat suppressed.
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