Non-coding RNAs in the interaction between rice and Meloidogyne graminicola

Underground communication: Long non-coding RNA signaling in the plant rhizosphere

Long non-coding RNAs (lncRNAs) have emerged as integral gene-expression regulators underlying plant growth, development, and adaptation. To adapt to the heterogeneous and dynamic rhizosphere, plants use interconnected regulatory mechanisms to optimally fine-tune gene-expression-governing interactions with soil biota, as well as nutrient acquisition and heavy metal tolerance. Recently, high-throughput sequencing has enabled the identification of plant lncRNAs responsive to rhizosphere biotic and abiotic cues. Here, we examine lncRNA biogenesis, classification, and mode of action, highlighting the functions of lncRNAs in mediating plant adaptation to diverse rhizosphere factors. We then discuss studies that reveal the significance and target genes of lncRNAs during developmental plasticity and stress responses at the rhizobium interface. A comprehensive understanding of specific lncRNAs, their regulatory targets, and the intricacies of their functional interaction networks will provide crucial insights into how these transcriptomic switches fine-tune responses to shifting rhizosphere signals. Looking ahead, we foresee that single-cell dissection of cell-type-specific lncRNA regulatory dynamics will enhance our understanding of the precise developmental modulation mechanisms that enable plant rhizosphere adaptation. Overcoming future challenges through multi-omics and genetic approaches will more fully reveal the integral roles of lncRNAs in governing plant adaptation to the belowground environment.

AUXIN RESPONSIVE FACTOR8 regulates development of the feeding site induced by root-knot nematodes in tomato

Root-knot nematodes (RKN) from the genus Meloidogyne induce the dedifferentiation of root vascular cells into giant multinucleate feeding cells. These feeding cells result from an extensive reprogramming of gene expression, and auxin is known to be a key player in their development. However, little is known about how the auxin signal is transmitted during giant cell development. Integrative analyses combining transcriptome and small non-coding RNA datasets with the specific sequencing of cleaved transcripts identified genes targeted by miRNAs in tomato (Solanum lycopersicum) galls. The two auxin-responsive transcription factors ARF8A and ARF8B, and their miRNA167 regulators, were identified as robust gene-miRNA pair candidates to be involved in the tomato response to M. incognita. Spatiotemporal expression analysis using promoter-β-glucuronidase (GUS) fusions showed the up-regulation of ARF8A and ARF8B in RKN-induced feeding cells and surrounding cells. The generation and phenotyping of CRISPR (clustered regularly interspaced palindromic repeats) mutants demonstrated the role of ARF8A and ARF8B in giant cell development and allowed the characterization of their downstream regulated genes.

Comprehensive transcriptomic analysis of three varieties with different brown planthopper-resistance identifies leaf sheath lncRNAs in rice

BACKGROUND

Long non-coding RNAs (lncRNAs) have been brought great attention for their crucial roles in diverse biological processes. However, systematic identification of lncRNAs associated with specialized rice pest, brown planthopper (BPH), defense in rice remains unexplored.

RESULTS

In this study, a genome-wide high throughput sequencing analysis was performed using leaf sheaths of susceptible rice Taichung Native 1 (TN1) and resistant rice IR36 and R476 with and without BPH feeding. A total of 2283 lncRNAs were identified, of which 649 lncRNAs were differentially expressed. During BPH infestation, 84 (120 in total), 52 (70 in total) and 63 (94 in total) of differentially expressed lncRNAs were found only in TN1, IR36 and R476, respectively. Through analyzing their cis-, trans-, and target mimic-activities, not only the lncRNAs targeting resistance genes (NBS-LRR and RLKs) and transcription factors, but also the lncRNAs acting as the targets of the well-studied stress-related miRNAs (miR2118, miR528, and miR1320) in each variety were identified. Before the BPH feeding, 238 and 312 lncRNAs were found to be differentially expressed in TN1 vs. IR36 and TN1 vs. R476, respectively. Among their putative targets, the plant-pathogen interaction pathway was significantly enriched. It is speculated that the resistant rice was in a priming state by the regulation of lncRNAs. Furthermore, the lncRNAs extensively involved in response to BPH feeding were identified by Weighted Gene Co-expression Network Analysis (WGCNA), and the possible regulation networks of the key lncRNAs were constructed. These lncRNAs regulate different pathways that contribute to the basal defense and specific resistance of rice to the BPH.

CONCLUSION

In summary, we identified the specific lncRNAs targeting the well-studied stress-related miRNAs, resistance genes, and transcription factors in each variety during BPH infestation. Additionally, the possible regulating network of the lncRNAs extensively responding to BPH feeding revealed by WGCNA were constructed. These findings will provide further understanding of the regulatory roles of lncRNAs in BPH defense, and lay a foundation for functional research on the candidate lncRNAs.

Roles of long non-coding RNAs in plant immunity

Robust plant immune systems are fine-tuned by both protein-coding genes and non-coding RNAs. Long non-coding RNAs (lncRNAs) refer to RNAs with a length of more than 200 nt and usually do not have protein-coding function and do not belong to any other well-known non-coding RNA types. The non-protein-coding, low expression, and non-conservative characteristics of lncRNAs restrict their recognition. Although studies of lncRNAs in plants are in the early stage, emerging studies have shown that plants employ lncRNAs to regulate plant immunity. Moreover, in response to stresses, numerous lncRNAs are differentially expressed, which manifests the actions of low-expressed lncRNAs and makes plant-microbe/insect interactions a convenient system to study the functions of lncRNAs. Here, we summarize the current advances in plant lncRNAs, discuss their regulatory effects in different stages of plant immunity, and highlight their roles in diverse plant-microbe/insect interactions. These insights will not only strengthen our understanding of the roles and actions of lncRNAs in plant-microbe/insect interactions but also provide novel insight into plant immune responses and a basis for further research in this field.

An OsPRMT5-OsAGO2/miR1875-OsHXK1 module regulates rice immunity to blast disease

Rice ARGONAUTE2 (OsAGO2) is a core component of the rice RNA-induced silencing complex (RISC), which is repressed by Magnaporthe oryzae (M. oryzae) infection. Whether and how OsAGO2-mediated gene silencing plays a role in rice blast resistance and which sRNAs participate in this process are unknown. Our results indicate that OsAGO2 is a key immune player that manipulates rice defense responses against blast disease. OsAGO2 associates with the 24-nt miR1875 and binds to the promoter region of HEXOKINASE1 (OsHXK1), which causes DNA methylation and leads to gene silencing. Our multiple genetic evidence showed that, without M. oryzae infection, OsAGO2/miR1875 RISC promoted OsHXK1 promoter DNA methylation and OsHXK1 silencing; after M. oryzae infection, the reduced OsAGO2/miR1875 led to a relatively activated OsHXK1 expression. OsHXK1 acts as a positive regulator of blast disease resistance that OsHXK1-OE rice exhibited enhanced resistance, whereas Cas9-Oshxk1 rice showed reduced resistance against M. oryzae infection. OsHXK1 may function through its sugar sensor activity as glucose induced defense-related gene expression and reactive oxygen species (ROS) accumulation in Nipponbare and OsHXK1-OE but not in Cas9-Oshxk1 rice. OsAGO2 itself is delicately regulated by OsPRMT5, which senses M. oryzae infection and attenuates OsAGO2-mediated gene silencing through OsAGO2 arginine methylation. Our study reveals an OsPRMT5-OsAGO2/miR1875-OsHXK1 regulatory module that fine tunes the rice defense response to blast disease.

Genome-wide identification of small interfering RNAs from sRNA libraries constructed from soybean cyst nematode resistant and susceptible cultivars

Plant small-RNAs regulate various biological processes by manipulating the expression of target genes at the transcriptional and post-transcriptional levels. However, little is known about the response and the functional roles of sRNAs, particularly small-interfering RNAs (siRNAs), in the soybean-soybean cyst nematode interaction. In this study, siRNA data from 24 sRNA libraries constructed from SCN-infected and non-SCN-infected resistant and susceptible soybean roots were analysed in silico. A total of 26 novel siRNAs including 17 phasiRNAs and 9 nat-siRNAs, as well as two phasiRNAs that were differentially expressed (DE) in three comparisons, were identified. Then, using qRT-PCR, the expression of majority of siRNAs was found to be downregulated after SCN infection, and the expression patterns of DE siRNAs were confirmed. Further functional annotation analyses revealed that the target genes of these siRNA were highly related to disease resistance, which included the genes coding for the NB-ARC domain, leucine-rich repeats, and Hs1pro-1 homologous proteins. Overall, the present research identified novel siRNAs and annotated their target genes, thereby laying the foundation for deciphering the roles of siRNAs in the soybean-SCN interaction.

Advances in Non-Coding RNA Sequencing

Non-coding RNAs (ncRNAs) comprise a set of abundant and functionally diverse RNA molecules. Since the discovery of the first ncRNA in the 1960s, ncRNAs have been shown to be involved in nearly all steps of the central dogma of molecular biology. In recent years, the pace of discovery of novel ncRNAs and their cellular roles has been greatly accelerated by high-throughput sequencing. Advances in sequencing technology, library preparation protocols as well as computational biology helped to greatly expand our knowledge of which ncRNAs exist throughout the kingdoms of life. Moreover, RNA sequencing revealed crucial roles of many ncRNAs in human health and disease. In this review, we discuss the most recent methodological advancements in the rapidly evolving field of high-throughput sequencing and how it has greatly expanded our understanding of ncRNA biology across a large number of different organisms.