Phenotypic and transcriptomic profiling of the interaction involving a virulent Meloidogyne javanica and a tomato genotype carrying the Mi-1.2 resistance gene

• Ano de defesa: 2024
• Autor(a) principal: Confort, Pedro Marcus de Souza
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Fitopatologia; Genes de resistência; Nematoide das galhas; Phytopatology; Resistance genes; RNAseq; Root gall nematodes
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/11/11151/tde-05082024-162450/

Global tomato crops face a substantial threat from root-knot nematodes (RKN), specially Meloidogyne incognita and M. javanica. These pathogens parasitize root cells, creating specialized feeding cells within abnormal root growths known as galls. This process results in diminished plant growth and, consequently, leads to yield losses. The impact of RKN on tomato yields fluctuates significantly based on specific environmental conditions. In general, medium infestations are associated with an overall yield reduction of 20-30%. The employment of the Mi-1.2 resistance gene is a crucial control strategy used to overcome this challenge. Nevertheless, emerging populations of virulent M. javanica and M. incognita pose a hindrance to the effectiveness of Mi-1.2. This study encompassed two lines of investigation. The first focused on examining the interaction between the susceptible tomato genotype \"Santa Clara\" (S) and the resistant \"Santy\" (R) in response to isolates of M. incognita and M. javanica, aiming to confirm the reproductive capacity of some of them in relation to the Mi-1.2 gene (R), present in the resistant tomato. In this stage, a productivity study was also conducted to observe the effects of avirulent and virulent isolates of M. javanica on the productivity of S and R tomato plants. In experiments conducted in a greenhouse, interactions were initially assessed between 4 isolates of M. incognita and 2 of M. javanica when inoculated in R and S hosts. Treatments were established based on the contrasts between isolates and hosts (6 x 2), with 8 biological replicas each. At the end of this stage, it was observed that an isolate of M. javanica (Vir) was able to reproduce in the presence of the Mi-1.2 gene. A second stage evaluated the impact of M. javanica infection on the development and productivity of tomato plants. Treatments consisted of contrasts between R and S hosts, Vir and Avir isolates (unable to reproduce in the presence of the Mi-1.2 gene), and two initial population densities (6 and 9 nematodes per cubic centimeter of soil). Additionally, 2 non-infested control treatments were added, totaling 10 treatments. The study demonstrated that an initial population of 6 specimens of M. javanica per cm3 can cause reductions in the productivity of tomatoes carrying the Mi-1.2 gene. To gain molecular insights, a following study explored the transcriptional responses of the \'Santy\' tomato genotype during both compatible and incompatible interactions with M. javanica isolates. RNA sequencing revealed differentially expressed genes (DEGs) associated with crucial biological responses to biotic stresses. Findings included the upregulation of resistance gene analogs and calmodulins in the incompatible interaction, suggesting a complex interplay between the plant\'s defense mechanisms and nematode virulence factors, including a candidate effector. In conclusion, this comprehensive study provides insights into the intricate dynamics of Mi-1.2 resistance in tomatoes against RNK. To this date, this is the only transcriptome analysis of the interaction between M. javanica x Solanum lycopersicum. And through it, we hope to enhances our comprehensive understanding of this plant-pathogen interactions, elucidating the molecular mechanisms that drive disease development and the erosion of Mi-1.2 resistance.