João Colaço
"The proposed work of this ViroiDoc project was a strong incentive for my application, to reengage my plant pathogen knowledge in the viroid field. I am enthusiastic about developing a workflow that uses trancriptomic data of infected plants and aims to infer host proteins that could play an impact in viroid infection. The possibility for academic mobility and joining a dynamic network was also crucial. This PhD project is an important steppingstone in my academic path, by helping me build a career as a scientific researcher and has the ultimate goal of ameliorating the losses in agriculture caused by viroid diseases. "
João is ViroiDoc MSCA fellow in Slovenia (DC1) at the Biotechnical Faculty of the University of Ljubljana (BF UL).
Individual Research Projects (IRP):
How Disrupting Viroid Biogenesis Impacts Viroid propagation
Viroids are the smallest known infectious agents affecting plants. They consist of circular, highly structured RNA molecules, ranging from 246 to 401 nucleotides in length, and notably without any coding potential. The viroid life cycle is therefore completely dependent on the host plant proteins and factors. Some of them are already characterized and they include: a) nuclear import proteins (e.g. VirP1 mediates nuclear import of viroids through importin-based pathway), b) RNA polymerase II machinery (e.g. a splice variant of transcription factor IIIA facilitates viroid replication, with functional organization of RNA Pol-II), c) processing enzymes (e.g. DNA ligase 1 is implicated in viroid circularization) and e) proteins involved in transportation from the nucleus to the cytoplasm and in cell-to-cell movement (potentially via the 5S rRNA export pathway). This doctoral project aims to identify any novel host proteins involved in viroid biogenesis and/or to confirm those already characterized by analyzing gene expression changes during viroid infections across plant species. We aim to collect and analyze publicly available RNA-seq datasets from various plant-viroid experiments to identify common and unique differentially expressed host transcripts and enriched pathways during viroid infection. Up to six candidate host genes will be selected and silenced either in hop (Humulus lupulus) or model plant (e.g. Nicotiana benthamiana) using virus-induced gene silencing (VIGS), followed by infection with selected viroid species (e.g. CBCVd, Cocadviroid rimocitri). After infection, viroid titers and disease symptoms will be monitored over a six-month period. RNA will be extracted at multiple time points post-inoculation to quantify CBCVd levels using RT-qPCR based on TaqMan approach, while disease symptoms and progression will be assessed using a scoring system. This doctoral project will provide new insights into how viroids interact with their host plants and helping to improve our understanding of the molecular processes involved in infection. This knowledge may offer a valuable basis for developing future breeding or preventive strategies to increase viroid resistance in important agricultural crops.
João Colaço, Helena Volk (UL), J-A. Daròs (CSIC), Nataša Štajner (UL), Jernej Jakše (UL)
The text above was submitted as poster abstract for the Viroids2025 conference in Bari, Italy.
Project presentation