RNA interference in the study and control of citrus phytopathogenic fungi

Author(s)

Eduardo Henrique Goulin

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2017-08-29

Examining board members

Marcos Antonio Machado; Nelson Sidnei Massola Júnior; Suzete Aparecida Lanza Destéfano; Edson Luiz Furtado; Jorge Mauricio Costa Mondego

• Advisor: Marcos Antonio Machado

Abstract

Since ancient times citrus is an economically important culture for many countries worldwide. Brazil is one of the largest producer and exporter of citrus and its derives, with most of orchards concentrated in the Southeast region of the country. Many phytopathogens are responsible for significant losses in citrus production and fruit quality. Postbloom fruit drop is one of the many fungal diseases that can attack the citrus crop. The disease is characterized by lesions on the petals that can extend to young fruits, inducing their early drop. One of the causal agents of this disease is Colletotrichum abscissum, which belongs to the Colletotrichum acutatum species complex. The disease control is based on chemical fungicides that block the fungus cell respiration. This form of control is also used to target cell respiration of another fungus, Phyllosticta citricarpa, causal agent of a different citrus disease, the citrus black spot. Since pathogen resistance for those chemical agents are frequently reported, new technologies are being developed to control this phytopathogens. One of these technologies is the RNA interference. In other to better understand the process and indicate strategies to control the postbloom fruit drop, the correct phylogenetic classification of an isolate of C. abscissum was made. Then, the whole genome sequencing and assembly of this fungus was performed. Therewith, genes of proteins related to the RNAi machinery were found, indicating the presence of this mechanism in C. abscissum, and also possible target genes for control by RNAi. Using these information, the functionality of the RNAi machinery was evaluated by effectively silencing of a reporter protein. Thereafter, endogenous genes that encode the subunits of enzymes related to cell respiration, which are targets of chemical fungicides, were silenced by RNAi indicating a perspective for the use of this strategy for postbloom fruit drop control, decreasing the chances of resistance, commonly associated to a single-point mutation. To evaluate the C. abscissum mutant pathogenicity alterations, an efficient and reliable in vitro symptom induction system was developed (AU)

• FAPESP's process: 12/23381-7 - Evaluation of transcriptome and potential candidate genes for RNAi sistyms in pathogenic fungi of citrus
• Grantee: Eduardo Henrique Goulin
• Support Opportunities: Scholarships in Brazil - Doctorate