Molecular Pathogens 2024, Vol.15, No.3, 155-169 http://microbescipublisher.com/index.php/mp 165 correlated with resistance (Wang et al., 2021). Similarly, transcriptome profiling of pumpkin leaves infected with PM has revealed differentially expressed genes (DEGs) such as bHLH87, ERF014, WRKY21, HSF, MLO3, and SGT1, which have distinct expression patterns in resistant versus susceptible plants (Guo et al., 2018). These genes are part of a broader regulatory network that includes hormone signal transduction pathways and defense responses. 7.3 Interaction between host plants and pathogens at the molecular level At the molecular level, the interaction between host plants and pathogens involves a dynamic exchange of signals and responses. Long noncoding RNAs (lncRNAs) and microRNAs (miRNAs) have been shown to play important roles in plant immunity, including the response to PM (Nie et al., 2021; Tian et al., 2022). For instance, differentially expressed lncRNAs and mRNAs have been identified in cucumber that correlate with resistance to PM, and these are associated with pathways such as phenylpropanoid biosynthesis and ubiquinone biosynthesis (Nie et al., 2021). In Cucurbita pepo, PM-responsive lncRNAs have been linked to various biological processes, including the plant-pathogen interaction pathway and the MAPK signaling pathway (Tian et al., 2022). These findings suggest that noncoding RNAs are integral components of the molecular mechanisms underlying resistance to PM in Cucurbitaceae plants. 8 Discussion 8.1 Synthesis of reviewed literature: major findings and their implications The collective research on PM in Cucurbitaceae plants has made significant strides in understanding the pathogenesis and resistance mechanisms against P. xanthii, the primary causal agent of the disease. The genome of P. xanthii has been characterized, providing a valuable resource for future genomic and proteomic studies aimed at understanding host-specific pathogenesis (Kim et al., 2020). This genomic information has been crucial in identifying candidate secreted effector proteins that play a role in the infection process, which could lead to the development of targeted strategies for disease prevention. Field trials and genetic studies have identified differences in resistance among Cucurbitaceae cultivars, with some showing promising resistance traits (Cohen et al., 2003; Caligiore-Gei, et al., 2022). For instance, the advanced breeding line BL717/1 has been highlighted as a potential source of resistance for the development of open-pollinated resistant cultivars (Caligiore-Gei et al., 2022). Additionally, the use of CRISPR/Cas9-mediated mutagenesis has been successful in generating PM resistance in cucumber by targeting the CsaMLO8 gene, which encodes a susceptibility factor for fungus penetration (Shnaider et al., 2022). This approach offers a direct method for enhancing resistance in commercial cultivars and hybrid parental lines, potentially simplifying the breeding process. The Mildew Locus O(MLO) gene family has been extensively studied, revealing its role as a susceptibility factor for PM. Inactivation of specific MLOgenes leads to a form of resistance known as mlo resistance, which has been observed in several Cucurbitaceae species (Iovieno et al., 2015). Furthermore, the identification of a single-gene resistance to PM in zucchini squash, designated Pm-0, derived from a wild species, has been a significant breakthrough in breeding resistant cultivars (Cohen et al., 2003; Holdsworth et al., 2016). Biocontrol agents, such as Bacillus amyloliquefaciens LJ02, have shown potential in inducing systemic resistance against cucurbits PM by stimulating the salicylic acid-mediated defense response (Li et al., 2015). This highlights the possibility of integrating biological control methods with traditional breeding approaches for disease management. 8.2 Comparison with resistance mechanisms in other plant families The resistance mechanisms observed in Cucurbitaceae share similarities with those in other plant families. For example, the role of MLOgenes in susceptibility to PM is not unique to Cucurbitaceae but has been documented in other families as well (Iovieno et al., 2015). The use of biocontrol agents to induce systemic resistance is also a common strategy across different plant species (Li et al., 2015).
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