RESUMO
BACKGROUND: The Mi-1 gene was the first identified and cloned gene that provides resistance to root-knot nematodes (RKNs) in cultivated tomato. However, owing to its temperature sensitivity, this gene does not meet the need for breeding disease-resistant plants that grow under high temperature. In this study, Mi-3 was isolated from the wild species PI 126443 (LA3858) and was shown to display heat-stable resistance to RKNs. However, the mechanism that regulates this resistance remains unknown. RESULTS: In this study, 4760, 1024 and 137 differentially expressed genes (DEGs) were enriched on the basis of pairwise comparisons (34 °C vs. 25 °C) at 0 (before inoculation), 3 and 6 days post-inoculation (dpi), respectively. A total of 7035 DEGs were identified from line LA3858 in the respective groups under the different soil temperature treatments. At 3 dpi, most DEGs were enriched in Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways related to plant biotic responses, such as "plant-pathogen interaction" and "plant hormone signal transduction". Significantly enriched DEGs were found to encode key proteins such as R proteins and heat-shock proteins (HSPs). Moreover, other DEGs were found to participate in Ca2+ signal transduction; the production of ROS; DEGs encoding transcription factors (TFs) from the bHLH, TGA, ERF, heat-shock transcription factor (HSF) and WRKY families were highly expressed, which contribute to be involved into the formation of phytohormones, such as salicylic acid (SA), jasmonic acid (JA) and ethylene (ET), the expression of most was upregulated at 3 dpi at the 25 °C soil temperature compared with the 34 °C soil temperature. CONCLUSION: Taken together, the results of our study revealed reliable candidate genes from wild materials LA3858, that are related to Mi-3-mediate resistance to Meloidogyne incognita. A large number of vital pathways and DEGs were expressed specifically in accession LA3858 grown at 34 °C and 25 °C soil temperatures at 3 dpi. Upon infection by RKNs, pattern-recognition receptors (PRRs) specifically recognized conserved pathogen-associated molecular patterns (PAMPs) as a result of pathogen-triggered immunity (PTI), and the downstream defensive signal transduction pathway was likely activated through Ca2+ signal channels. The expression of various TFs was induced to synthesize phytohormones and activate R proteins related to resistance, resulting in the development of effector-triggered immunity (ETI). Last, a hypersensitive response in the roots occurred, which was probably induced by the accumulation of ROS.
Assuntos
Resistência à Doença/genética , Interações Hospedeiro-Parasita/genética , Proteínas de Plantas/metabolismo , Solanum/genética , Solanum/metabolismo , Animais , Cálcio/metabolismo , Ciclopentanos/metabolismo , Etilenos/metabolismo , Regulação da Expressão Gênica de Plantas , Ontologia Genética , Proteínas de Choque Térmico/genética , Proteínas de Choque Térmico/metabolismo , Oxilipinas/metabolismo , Proteínas de Plantas/genética , Raízes de Plantas/genética , Raízes de Plantas/metabolismo , RNA-Seq , Espécies Reativas de Oxigênio , Ácido Salicílico/metabolismo , Transdução de Sinais/genética , Solanum/imunologia , Solanum/parasitologia , Temperatura , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Transcriptoma/genética , Tylenchoidea/patogenicidadeRESUMO
BACKGROUND: During tomato cultivation, tomato leaf mould is a common disease caused by Cladosporium fulvum (C. fulvum). By encoding Cf proteins, which can recognize corresponding AVR proteins produced by C. fulvum, Cf genes provide resistance to C. fulvum, and the resistance response patterns mediated by different Cf genes are not identical. Plants carrying the Cf-19 gene show effective resistance to C. fulvum in the field and can be used as new resistant materials in breeding. In this study, to identify key regulatory genes related to resistance and to understand the resistance response process in tomato plants carrying Cf-19, RNA sequencing (RNA-seq) was used to analyse the differences between the response of resistant plants (CGN18423, carrying the Cf-19 gene) and susceptible plants (Moneymaker (MM), carrying the Cf-0 gene) at 0, 7 and 20 days after inoculation (dai). RESULTS: A total of 418 differentially expressed genes (DEGs) were identified specifically in the CGN18423 response process. Gene Ontology (GO) analysis revealed that GO terms including "plasma membrane (GO_Component)", "histidine decarboxylase activity (GO_Function)", and "carboxylic acid metabolic process (GO_Process)", as well as other 10 GO terms, were significantly enriched. The "plant hormone signal transduction" pathway, which was unique to CGN18423 in the 0-7 dai comparison, was identified. Moreover, ten key regulatory points were screened from the "plant hormone signal transduction" pathway and the "plant pathogen interaction" pathway. Hormone content measurements revealed that the salicylic acid (SA) contents increased and peaked at 7 dai, after which the contents deceased and reached minimum values in both CGN18423 and MM plants at 20 dai. The jasmonic acid (JA) content increased to a very high level at 7 dai but then decreased to nearly the initial level at 20 dai in CGN18423, while it continued to increase slightly during the whole process from 0 to 20 dai in MM. CONCLUSIONS: The initial responses are very different between the resistant and susceptible plants. The "plant hormone signal transduction" pathway is important for the formation of Cf-19-mediated immunity. In addition, both JA and SA play roles in regulating the Cf-19-dependent resistance response.
