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Long non-coding RNAs (lncRNAs) are emerging as important regulators of various aspects of immune response and plant-pathogen interactions. However, the regulatory function of lncRNAs during plant-nematode interaction remain largely elusive. In this study, we investigated the differential regulation and function of lncRNAs during two different stages of tomato infection by the root-knot nematode Meloidogyne incognita . At the early stage of infection, 2218 and 2827 lncRNAs were regulated locally in the M. incognita -induced galls and systemically in the neighboring root cells, respectively. However, at the later stage of infection, the number of M. incognita -regulated lncRNAs was dramatically reduced with only 49 lncRNA being identified as differentially expressed. Differentially expressed lncRNAs were predicted to encode peptides with functionally annotated domains, providing insights into the potential roles of these peptides in regulating gene expression, RNA stability and splicing, and protein-protein-interactions. Among the differentially expressed lcRNAs, 55 were found to contain putative binding sites for 56 miRNAs. Overexpressing 5 of these lncRNAs significantly increased tomato resistance to M. incognita , supporting the functional importance of lncRNAs for establishing tomato- M. incognita interaction. Functional analysis of the target mimicry of lncRNAs towards miRNAs resulted in the identification of two novel regulatory modules involving miR47 and miR156e-5p and their targeted genes that regulate tomato responses to M. incognita parasitism. Taken together, our data provide novel insights into the transcriptional and post-transcriptional regulatory functions of lncRNA, and open a new avenue to engineer crop plants with enhanced nematode resistance by leveraging the regulatory potential of lncRNAs.

Various species of rhizobium establish compatible symbiotic relationships with soybean ( Glycine max ) leading to the formation of nitrogen-fixing nodules in roots. The formation of functional nodules is mediated through complex developmental and transcriptional reprogramming that involves the activity of thousands of plant genes. However, host transcriptome that differentiate between functional or non-functional nodules remain largely unexplored. In this study, we investigated differential compatibilities between rhizobium strains ( Bradyrhizobium diazoefficiens USDA110 Bradyrhizobium sp. strain LVM105) and cultivated and wild soybeans. The nodulation assays revealed that both USDA110 and LVM105 strains effectively nodulate G. soja but only USDA110 can form symbiotic relationships with Williams 82. LVM105 formed pseudonodules on Williams 82 that consist of a central nodule-like mass that are devoid of any rhizobia. RNA-seq data revealed that USDA110 and LVM105 induce distinct transcriptome programing in functional mature nodules formed on G. soja roots, where genes involved in nucleosome assembly, DNA replication, regulation of cell cycle, and defense responses play key roles. Transcriptome comparison also suggested that activation of genes associated with cell wall biogenesis and organization and defense responses together with downregulation of genes involved in the biosynthesis of isoprenoids and antioxidant stress are associated with the formation of non-functional nodules on Williams 82 roots. Moreover, our analysis implies that increased activity of genes involved in oxygen binding, amino acid transport, and nitrate transport differentiates between fully-developed nodules in cultivated versus wild soybeans., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Zadegan, Kim, Abbas, Kim, Krishnan and Hewezi.)

An increasing number of metazoans undergo programmed DNA elimination (PDE), where a significant amount of DNA is selectively lost from the somatic genome during development. In some nematodes, PDE leads to the removal and remodeling of the ends of all germline chromosomes. In several species, PDE also generates internal breaks that lead to sequence loss and increased numbers of somatic chromosomes. The biological significance of these karyotype changes associated with PDE and the origin and evolution of nematode PDE remain largely unknown. Here, we assembled the single germline chromosome of the nematode Parascaris univalens and compared the karyotypes, chromosomal gene organization, and PDE features among other nematodes. We show that PDE in Parascaris converts an XX/XY sex-determination system in the germline into an XX/XO system in the somatic cells. Comparisons of Ascaris, Parascaris, and Baylisascaris ascarid chromosomes suggest that PDE existed in the ancestor of these nematodes, and their current distinct germline karyotypes were derived from fusion events of smaller ancestral chromosomes. The DNA breaks involved in PDE resolve these fused germline chromosomes into their pre-fusion karyotypes. These karyotype changes may lead to alterations in genome architecture and gene expression in the somatic cells. Cytological and genomic analyses further suggest that satellite DNA and the heterochromatic chromosome arms are dynamic and may play a role during meiosis. Overall, our results show that chromosome fusion and PDE have been harnessed in these ascarids to sculpt their karyotypes, altering the genome organization and serving specific functions in the germline and somatic cells., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Mitogen-activated protein kinase (MPK) cascades play central signalling roles in plant immunity and stress response. The soybean orthologue of MPK kinase2 (GmMKK2) was recently identified as a potential signalling node whose expression is upregulated in the feeding site induced by soybean cyst nematode (SCN, Heterodera glycines). To investigate the role of GmMKK2 in soybean-SCN interactions, we overexpressed a catabolically inactive variant referred to as kinase-dead variant (KD-GmMKK2) using transgenic hairy roots. KD-GmMKK2 overexpression caused significant reduction in soybean susceptibility to SCN, while overexpression of the wild-type variant (WT-GmMKK2) exhibited no effect on susceptibility. Transcriptome analysis indicated that KD-GmMKK2 overexpressing plants are primed for SCN resistance via constitutive activation of defence signalling, particularly those related to chitin, respiratory burst, hydrogen peroxide and salicylic acid. Phosphoproteomic profiling of the WT-GmMKK2 and KD-GmMKK2 root samples upon SCN infection resulted in the identification of 391 potential targets of GmMKK2. These targets are involved in a broad range of biological processes, including defence signalling, vesicle fusion, chromatin remodelling and nuclear organization among others. Furthermore, GmMKK2 mediates phosphorylation of numerous transcriptional and translational regulators, pointing to the presence of signalling shortcuts besides the canonical MAPK cascades to initiate downstream signalling that eventually regulates gene expression and translation initiation. Finally, the functional requirement of specific phosphorylation sites for soybean response to SCN infection was validated by overexpressing phospho-mimic and phospho-dead variants of two differentially phosphorylated proteins SUN1 and IDD4. Together, our analyses identify GmMKK2 impacts on signalling modules that regulate soybean response to SCN infection., (© 2024 The Authors. Molecular Plant Pathology published by British Society for Plant Pathology and John Wiley & Sons Ltd.)

Epigenetic modifications including miRNA regulation, DNA methylation, and histone modifications play fundamental roles in establishing the interactions between host plants and parasitic nematodes. Over the past decade, an increasing number of studies revealed the key functions of various components of the plant epigenome in the regulation of gene expression and shaping plant responses to nematode infection. In this chapter, we provide a conceptual framework for methods used to investigate epigenetic regulation during plant-nematode interactions. We focus specifically on current and emerging methods used to study miRNA regulation and function. We also highlight various methods and analytical tools used to profile DNA methylation patterns and histone modification marks at the genome level. Our intention is simply to explain the advantages of various methods and how to overcome some limitations. With rapid development of single-cell sequencing technology and genome editing, advanced and new methodologies are expected to emerge in the near future to further improve our understanding of epigenetic regulation and function during plant-nematode interactions., (© 2024. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

BAK1-INTERACTING RECEPTOR LIKE KINASE1 (BIR1) is a negative regulator of various aspects of disease resistance and immune responses. Here, we investigated the functional role of soybean (Glycine max) BIR1 (GmBIR1) during soybean interaction with soybean cyst nematode (SCN, Heterodera glycines) and the molecular mechanism through which GmBIR1 regulates plant immunity. Overexpression of wild-type variant of GmBIR1 (WT-GmBIR1) using transgenic soybean hairy roots significantly increased soybean susceptibility to SCN, whereas overexpression of kinase-dead variant (KD-GmBIR1) significantly increased plant resistance. Transcriptome analysis revealed that genes oppositely regulated in WT-GmBIR1 and KD-GmBIR1 upon SCN infection were enriched primarily in defense and immunity-related functions. Quantitative phosphoproteomic analysis identified 208 proteins as putative substrates of the GmBIR1 signaling pathway, 114 of which were differentially phosphorylated upon SCN infection. In addition, the phosphoproteomic data pointed to a role of the GmBIR1 signaling pathway in regulating alternative pre-mRNA splicing. Genome-wide analysis of splicing events provided compelling evidence supporting a role of the GmBIR1 signaling pathway in establishing alternative splicing during SCN infection. Our results provide novel mechanistic insights into the function of the GmBIR1 signaling pathway in regulating soybean transcriptome and spliceome via differential phosphorylation of splicing factors and regulation of splicing events of pre-mRNA decay- and spliceosome-related genes., (© 2023 The Authors New Phytologist © 2023 New Phytologist Foundation.)

Gene co-expression network analysis is an efficient systems biology approach for the discovery of novel gene functions and trait-associated gene modules. To identify clusters of functionally related genes involved in soybean nodule formation and development, we performed a weighted gene co-expression network analysis. Two nodule-specific modules (NSM-1 and NSM-2, containing 304 and 203 genes, respectively) were identified. The NSM-1 gene promoters were significantly enriched in cis-binding elements for ERF, MYB, and C2H2-type zinc transcription factors, whereas NSM-2 gene promoters were enriched in cis-binding elements for TCP, bZIP, and bHLH transcription factors, suggesting a role of these regulatory factors in the transcriptional activation of nodule co-expressed genes. The co-expressed gene modules included genes with potential novel roles in nodulation, including those involved in xylem development, transmembrane transport, the ethylene signalling pathway, cytoskeleton organization, cytokinesis and regulation of the cell cycle, regulation of meristem initiation and growth, transcriptional regulation, DNA methylation, and histone modifications. Functional analysis of two co-expressed genes using TILLING mutants provided novel insight into the involvement of unsaturated fatty acid biosynthesis and folate metabolism in nodule formation and development. The identified gene co-expression modules provide valuable resources for further functional genomics studies to dissect the genetic basis of nodule formation and development in soybean., (© 2023 The Authors. Molecular Plant Pathology published by British Society for Plant Pathology and John Wiley & Sons Ltd.)

Programmed DNA elimination (PDE) is a notable exception to the paradigm of genome integrity. In metazoa, PDE often occurs coincident with germline to somatic cell differentiation. During PDE, portions of genomic DNA are lost, resulting in reduced somatic genomes. Prior studies have described the sequences lost, as well as chromosome behavior, during metazoan PDE. However, a system for studying the mechanisms and consequences of PDE in metazoa is lacking. Here, we present a functional and genetic model for PDE in the free-living Rhabditidae nematode Oscheius tipulae, a family that also includes Caenorhabditis elegans. O. tipulae was recently suggested to eliminate DNA. Using staged embryos and DNA FISH, we showed that O. tipulae PDE occurs during embryogenesis at the 8-16 cell stages. We identified a conserved motif, named Sequence For Elimination (SFE), for all 12 break sites on the six chromosomes at the junctions of retained and eliminated DNA. SFE mutants exhibited a "fail-to-eliminate" phenotype only at the modified sites. END-seq revealed that breaks can occur at multiple positions within the SFE, with extensive end resection followed by telomere addition to both retained and eliminated ends. We identified many functional SFEs at the chromosome ends through END-seq in the wild-type embryos, genome sequencing of SFE mutants, and comparative genomics of 23 wild isolates. We suggest that these alternative SFEs provide flexibility in the sequences eliminated and a fail-safe mechanism for PDE. These studies establish O. tipulae as a new, attractive model for studying the mechanisms and consequences of PDE in a metazoan., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2022 Elsevier Inc. All rights reserved.)