Genetic toolbox and regulatory circuits of plant-nematode associations

Plant-nematode associations are the most imperative area of study that forms the basis to understand their regulatory networks and coordinated functional aspects. Nematodes are highly parasitic organisms known so far, to cause relentless damage towards agricultural crops on a global scale. They pierce the roots of host plants and form neo-plastic feeding structures to extract out resources for their functional development. Moreover, they undergo re-differentiation within plant cells to form giant multi-nucleate feeding structures or syncytium. All these processes are facilitated by numerous transcriptomic, proteomic, metabolomic and epigenetic modifications, that regulate different biological attractions among plants and nematodes. Nevertheless, these mechanisms are quite remarkable and have been explored in the present review. Here, we have shed light on genomic as well as genetic approaches to acquire an effective understanding regarding plant-nematode associations. Transcriptomics have revealed an extensive network to unravel feeding mechanism of nematodes through geneexpression programming of target genes. Also, the regulatory circuits of epigenetic alterations through DNAmethylation, non-coding RNAs and histone modifications very well explain epigenetic profiling within plants. Since decades, research have observed many intricacies to elucidate the dynamic nature of epigenetic modulations in plant-nematode attractions. By this review, we have highlighted the functional aspects of small RNAs in inducing plant-nematode parasitism along with the putative role of miRNAs. These RNAs act as chief genetic elements to mediate the expressional changes in plants through post-transcriptional silencing of various effector proteins as well as transcriptional factors. A pragmatic role of miRNAs in modulating gene expression in nematode infection and feeding site development have also been reviewed. Hence, they have been considered master regulators for functional reprogramming the expression during establishment of feeding sites. We have also encapsulated the advancement of genome-broadened DNA-methylation and untangled the nematode mediated dynamic alterations within plant methylome along with assessing transcriptional activities of various genes and transposons. In particular, we have highlighted the role of effector proteins in stimulating epigenetic changes. Finally, we have emerged towards a molecular-based core understanding about plant-nematode associations.