Abstract
Phytophthora parasitica is one of the most widespread Phytophthora species, which is known to cause multiple diseases in tomato and is capable of infecting almost all plant parts. Our current understanding of tomato-Phytophthora parasitica interaction is very limited and currently nothing is known at the whole genome or transcriptome level. In this study, we have analyzed and compared the transcriptome of a resistant and a susceptible wild tomato accession in response to P. parasitica infection using the RNA-seq technology. We have identified 2657 and 3079 differentially expressed genes (DEGs) in treatment vs control comparison of resistant (Sp-R) and susceptible (Sp-S) samples respectively. Functional annotation of DEGs revealed substantial transcriptional reprogramming of diverse physiological and cellular processes, particularly the biotic stress responses in both Sp-R and Sp-S upon P. parasitica treatment. However, subtle expression differences among some core plant defense related genes were identified and their possible role in resistance development against P. parasitica is discussed. Our results revealed 1173 genes that were differentially expressed only in Sp-R accession upon P. parasitica inoculation. These exclusively found DEGs in Sp-R accession included some core plant defense genes, for example, several protease inhibitors, chitinases, defensin, PR-1, a downy mildew susceptibility factor, and so on, were all highly induced. Whereas, several R genes, WRKY transcriptions factors and a powdery mildew susceptibility gene (Mlo) were highly repressed during the resistance outcome. Analysis reported here lays out a strong foundation for future studies aimed at improving genetic resistance of tomato cultivars against to Phytopphthora species.
Highlights
Plants are constantly attacked by numerous microbes, insects and herbivores
If the plant is immune to the attacking pathogen the second layer of immunity called effector triggered immunity (ETI) comes in action, where the effectors themselves or the defense modulations caused by them are perceived by plants through a molecular machinery coded by the resistance genes (R genes) that leads to the activation of downstream components of defense leading to local cell death or hypersensitive response (HR) to prevent the spread of the pathogen
Localized HR-like lesion was observed on the leaves of Sp-R leading to pathogen’s growth arrest and no disease whereas water soaked lesions were observed on the leaves of susceptible accession (Sp-S) that resulted in severe disease development and visible pathogen growth and sporulation on the leaf surface (Figure 1)
Summary
Plants can’t escape from these invaders like other motile organisms They have evolved strong and sophisticated defense strategies to counter these attackers. Induced defense of plants comprises of two major layers, the first one is known as pathogen associated molecular pattern (PAMP) triggered immunity (PTI) in which some molecules or structures of pathogen are perceived by plant pattern recognition receptors (PRRs), followed by an array of defense responses that combat pathogen invasion. If the plant is immune to the attacking pathogen the second layer of immunity called effector triggered immunity (ETI) comes in action, where the effectors themselves or the defense modulations caused by them are perceived by plants through a molecular machinery coded by the resistance genes (R genes) that leads to the activation of downstream components of defense leading to local cell death or hypersensitive response (HR) to prevent the spread of the pathogen
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