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

Abstract

Reactions that occur when a plant is subjected to Citrus tristeza virus (CTV) infection often result in triggering of numerous defence mechanisms to fight the infection. The reactions vary according to virus strain, host genotype, time of exposure to the infection and environmental conditions. To date, no study has examined in detail the consequences of 10‐year exposure to CTV infection on the biochemical and physiological status of susceptible Mexican lime plants (Citrus aurantifolia). To understand the reaction of such plants, changes in nutrient status, total proteins, enzyme activity involved in scavenging of reactive oxygen species, photosynthetic and transpiration rates, chlorophyll content, membrane permeability and water content were analysed in plants infected with different CTV isolates and in healthy plants. The activity of superoxide dismutase and polyphenol oxidase significantly decreased in the infected leaves, and membrane permeability was lower in the infected plants. Macro‐ and micronutrient elements were significantly changed: concentrations of leaf nitrogen, zinc, magnesium and iron were elevated but potassium concentration depressed in comparison to noninfected control leaves. Levels of other analysed nutrient elements, enzymes, photosynthesis and stomatal conductance, chlorophyll content and relative water content were unchanged. Clear physiological changes were found among infected and noninfected control plants but none between plants infected with different CTV isolates. The data suggest that some of the defence mechanisms investigated here were suppressed due to the continuous and long‐term pressure of biotic stress.

The effect of drought conditions on sweet orange (Citrus sinensis) plants infected with citrus tristeza virus (CTV)

“…However, our results agree with data presented by Dória et al (2015), who found that catalase activity was not different between healthy and CTV-infected plants. According to Hančević et al (2018), infection by different CTV isolates does not interfere in the activity of this enzyme. Biochemical responses in plant defense against pathogens are performed by several enzymes, not only by catalase, and these can reduce the damage caused by the pathogen or prevent its progression in host plant tissues (Resende et al 2003).…”

The unknown soldier in citrus plants: polyamines-based defensive mechanisms against biotic and abiotic stresses and their relationship with other stress-associated metabolites

“…236 However, The enzymatic activities of SOD and polyphenol oxidase (PPO) were significantly reduced in Mexican lime (C. aurantifolia) plants after ten years of exposure to CTV infection. 254 These findings suggest that the antioxidant defense mechanisms might be suppressed by CTV because of continuous and long-term stress.…”

“…The CTV infection induced the generation of ROS in the infected cells, which subsequently reprogramming both primary and secondary metabolic pathways 240 and influencing the antioxidant enzymes activity. 236,254 For instance, the transcripts and enzymatic activity of superoxide dismutase (SOD) and ascorbate peroxidase (APX) were increased in sweet orange (C. sinensis cv. 'Westin') plants upon the CTV infection, while the activity of guaiacol peroxidase (GPX) did not change significantly.…”

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].…”