Citrus tristeza virus (CTV) Causing Proteomic and Enzymatic Changes in Sweet Orange Variety “Westin”

Abstract

Citrus Tristeza disease, caused by CTV (Citrus tristeza virus), committs citrus plantations around the world and specifically attacks phloem tissues of the plant. The virus exists as a mixture of more or less severe variants, which may or may not cause symptoms of Tristeza. The objective of this study was to analyze the changes caused by CTV in the proteome of stems of sweet orange, as well as in the activity and gene expression of antioxidant enzymes. The CTV-infected sweet orange displayed mild symptoms, which were characterized by the presence of sparse stem pitting throughout their stems. The presence of virus was confirmed by RT-PCR. Proteomic analysis by 2DE-PAGE-MS / MS revealed the identity of 40 proteins differentially expressed between CTV- infected and -non-infected samples. Of these, 33 were up-regulated and 7 were down-regulated in CTV-infected samples. Among the proteins identified stands out a specific from the virus, the coat protein. Other proteins identified are involved with oxidative stress and for this their enzymatic activity was measured. The activity of superoxide dismutase (SOD) was higher in CTV-infected samples, as catalase (CAT) showed higher activity in uninfected samples. The activity of guaiacol peroxidase (GPX) did not vary significantly between samples. However, ascorbate peroxidase (APX) was more active in the infected samples. The relative expression of the genes encoding CAT, SOD, APX and GPX was analyzed by quantitative real time PCR (RT-qPCR). The CTV-infected samples showed greater accumulation of transcripts, except for the CAT gene. This gene showed higher expression in the uninfected samples. Taken together, it can be concluded that the CTV affects the protein profile and activity and gene expression of antioxidant enzymes in plants infected by this virus.

Biochemical and physiological responses to long‐term Citrus tristeza virus infection in Mexican lime plants

“…Nitrogen is a major constituent of both host cell and viral nucleic acids and proteins. Elevated viral proteins and nucleic acid content together with known CTV influence on protein profile and activity (Dória et al ., ) might lead to increased N levels in leaves, similar to the general increase of total N in virus‐infected plants reported for other host–virus combinations (Sinha & Srivastava, ). Some studies have suggested the relationship between elevated leaf N concentration and susceptibility to virus infection to be caused by the formation of virus particles, despite significant correlation between these two parameters (Iqbal et al ., ; Ashfaq et al ., ).…”

“…SODs are the most important group of metalloenzymes and are considered as the first defence against ROS. Many authors have found changes in SOD activity in different plant species and cultivars in response to virus infection (Clarke et al, 2002;Siddique et al, 2014;D oria et al, 2015). In some cases the activity rises, in others SOD activity is suppressed, but it seems that it is initially genotype-dependent and that resistant genotypes develop higher SOD activities upon the virus infection as a plant strategy to restrict virus multiplication.…”

The p33 protein of Citrus tristeza virus affects viral pathogenicity by modulating a host immune response

“…Based on transcriptomic analyses, 334 genes in Mexican lime ( C. aurantifolia ) were found to respond to infection by a severe CTV isolate (T305), and 28% of these regulated genes were related to the stress and defense responses (Gandía et al ., ). A proteomic study showed that CTV infection causes changes in the protein profile/activity and gene expression of antioxidant enzymes in sweet orange ( C. sinensis ) (Dória et al ., ). Another proteomic analysis revealed that rootstock–scion crosstalk also influences citrus response to CTV.…”

An Overview on Citrus Mal Secco Disease: Approaches and Strategies to Select Tolerant Genotypes in C. limon

“…Huanglongbing (HLB) Proteomics [142] Proteomics; nutrient analysis [143] Proteomics; enzyme activity; reverse genetic [144] Transcriptomics ( Microarray) [145] Transcriptomics (RNASeq) [137,138,146] Transcriptomics (RNASeq); proteomics; FISH [147] Transcriptomics (qPCR); physiology; hormone content [148,149] Phytophthora spp Metabolomics [150] Transcriptomics (RNASeq) [151] Xanthomonas citri Metabolomics [152] Proteomics [153,154] Proteomics; structural study; enzyme activity; reverse genetic [155] Citrus Tristeza Virus Metabolomics; physiology; hormone content [156,157] Proteomics; enzyme activity [158] Reverse genetic [159,160] Transcriptomics (qPCR) [161,162] Transcriptomics (RNASeq) [146,163] Mal secco Proteomics; metabolomics; physiology [164] Transcriptomics (SSH) [40] Unlike to other citrus diseases, such as Phytophthora spp., [137,138,142,145], sometimes together with multidisciplinary approaches [139,165,166], identifying many candidates and regulated genes. Other works are focused to identify potential genotypes tolerant to CTV by qPCR [162] or to highlight the differentially expressed transcripts (DETs) after combined infection with different virus (HLB and CTV) [146].…”