Global Transcriptomic Analysis Reveals Insights into the Response of ‘Etrog’ Citron (Citrus medica L.) to Citrus Exocortis Viroid Infection

Abstract

Citrus exocortis viroid (CEVd) is the causal agent of citrus exocortis disease. We employed CEVd-infected ‘Etrog’ citron as a system to study the feedback regulation mechanism using transcriptome analysis in this study. Three months after CEVd infection, the transcriptome of fresh leaves was analyzed, and 1530 differentially expressed genes were detected. The replication of CEVd in citron induced upregulation of genes encoding key proteins that were involved in the RNA silencing pathway such as Dicer-like 2, RNA-dependent RNA polymerase 1, argonaute 2, argonaute 7, and silencing defective 3, as well as those genes encoding proteins that are related to basic defense responses. Many genes involved in secondary metabolite biosynthesis and chitinase activity were upregulated, whereas other genes related to cell wall and phytohormone signal transduction were downregulated. Moreover, genes encoding disease resistance proteins, pathogenicity-related proteins, and heat shock cognate 70 kDa proteins were also upregulated in response to CEVd infection. These results suggest that basic defense and RNA silencing mechanisms are activated by CEVd infection, and this information improves our understanding of the pathogenesis of viroids in woody plants.

Root Transcriptomic Analysis Reveals Global Changes Induced by Systemic Infection of Solanum lycopersicum with Mild and Severe Variants of Potato Spindle Tuber Viroid

“…Implementation of high-throughput methods, including microarray and RNA-seq technology, enable wide transcriptome profiling, which is very helpful in understanding the molecular basis of plant/host-pathogen interactions. Taking advantage of these technologies, there are many studies about leaf transcriptome analysis during viroid infection in various host plants, including PSTVd [10,11,12,13,14], citrus exocortis viroid (CEVd) [15,16,17], citrus viroid III (CVd-III) [18], peach latent mosaic viroid (PLMVd) [19], hop stunt viroid (HSVd) [20,21], chrysanthemum stunt viroid CSVd) [22], hop latent viroid (HLVd) [23,24], and citrus bark cracking viroid (CBCVd) [23,24,25]. Moreover, there is also data about gene expression alterations in PSTVd-infected tubers [26].…”

Ethylene is Involved in Symptom Development and Ribosomal Stress of Tomato Plants upon Citrus Exocortis Viroid Infection

“…Citrus exocortis viroid (CEVd), which belongs to the Pospiviroidae family, consists of around 370 nucleotides and has a broad range of hosts including tomato plants (Solanum lycopersicum L.). CEVd symptoms in tomato include stunting, epinasty, midvein necrosis, chlorosis and leaf rugosity [4][5][6]. Some of these symptoms have been associated with those produced by ethylene, since plants exogenously treated with the ethylene-releasing compound ethephon, as well as mutants that over produce ethylene, display similar symptoms to those caused by CEVd [7][8][9].…”

Identification and Molecular Mechanisms of Key Nucleotides Causing Attenuation in Pathogenicity of Dahlia Isolate of Potato Spindle Tuber Viroid

“…Changes in host transcriptome caused by viroid infection have been analyzed in various viroid–host combinations [ 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 ]. Infected plants are characterized by the fluctuations in several observables such as expressions of genes involved in plant innate immunity, defense responses, signal transduction and hormone metabolism.…”

“…Furthermore, it was shown in various viroid–host combinations that genes involved in plant innate immunity, mainly calcium-dependent protein kinase and mitogen-activated protein kinase cascade or genes involved in hypersensitive response, cell wall enhancement, and hormone signaling were activated by viroid infection. These observations also suggested that the expression of a large number of genes, such as those involved in defense responses, hormone metabolisms, signal transduction, photosynthesis, chloroplast, cell wall, and regulation of RNA expression are affected by viroid infection, leading to the development of disease symptoms [ 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 ].…”