Study on RNAi-based herbicide for Mikania micrantha

RNAi technology development for weed control: all smoke and no fire?

RNA interference (RNAi) technology, specifically Spray-Induced Gene Silencing (SIGS), holds potential as an innovative approach for selective weed control, promising environmentally friendly alternatives to traditional herbicides. Although the development of RNAi-based crop protection agents against pathogens, insects and viruses is advancing rapidly, RNAi-based weed control remains in the nascent stages, with challenges in gene target specificity and effective delivery mechanisms. It is potentially a game-changer in agriculture, yet SIGS's applicability is limited by the lack of scientific evidence. The overall aim of this review is to focus attention on critical points that need to be addressed to advance the knowledge about and development of RNAi herbicides, and overcome the poor progress achieved so far. Enhancing RNAi delivery methods and focusing on high impact weed species could transform SIGS into a viable tool for sustainable agriculture. © 2025 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Spray-induced gene silencing for crop protection: recent advances and emerging trends

The RNA-based spray-induced gene silencing (SIGS) technology represents an ecologically sustainable approach to crop protection and pathogen management. Following the recent approval of Ledprona as the first sprayable double-stranded RNA (dsRNA) biopesticide by the EPA at the end of 2023, SIGS has emerged as a focal point in both academic and industrial sectors. This review analyzes recent advances and emerging trends in SIGS. The application of SIGS for crop protection, including the control of insects, fungal pathogens, and viruses, is briefly summarized. Distinguishing this review from others, we delve into practical aspects of the technology, such as the selection and screening of target genes, large-scale production methods, and delivery systems, highlighting major advancements in these areas and also addressing the remaining questions and issues, particularly concerning safety concerns and controlling harmful weeds. Finally, this review emphasizes the emerging trends in SIGS technology, particularly its integration with nanotechnology and other methodologies. Collectively, the rapid progress in SIGS studies is poised to accelerate the maturation and application of this technology.

Genome-wide identification and expression analysis of the WRKY gene family in Mikania micrantha

BACKGROUND

WRKY transcription factors (TFs) regulate plant responses to environmental stimuli and development, including flowering. Despite extensive research on different species, their role in the invasive plant Mikania micrantha remains to be explored. The aim of this study was to identify and analyze WRKY genes in M. micrantha to understand their function in flowering and adaptation mechanisms.

RESULTS

By analysing the whole genome of M. micrantha, a total of 77 M. micrantha WRKY (MmWRKY) genes were identified. Based on phylogenetic relationships, sequence alignment, and structural domain diversity, the MmWRKY gene family was preliminarily classified into three major groups and five subgroups: Group I, Group II (II-a, II-b, II-c, II-d, II-e), and Group III. Expression profiles showed tissue-specific expression patterns, with many WRKY genes highly expressed in flowers, indicating potential roles in floral development. Real-time quantitative PCR confirmed that the selected 11 genes were highly expressed in floral tissues, supporting their functional significance in flowering.

CONCLUSION

In this study, 77 WRKY genes were identified in M micrantha, and their phylogenetic relationships, structural domains, and expression patterns across various tissues and organs were comprehensively analyzed. This work provides a foundation for future functional characterization of WRKY genes in M. micrantha, which may contribute to the development of more effective strategies to control its rapid spread.

Silencing of the MP Gene via dsRNA Affects Root Development and Growth in the Invasive Weed Mikania micrantha

Mikania micrantha ("mile-a-minute" weed) is a global invasive alien weed that can cause severe damage to agroforestry ecosystems and significant agricultural losses worldwide. Although chemical, manual, or mechanical control methods are widely used to control M. micrantha, RNA interference (RNAi)-based biocontrol methods have rarely been reported for this species. The MONOPTEROS (MP) gene, encoding an auxin response factor, plays an essential role in embryonic root initiation in Arabidopsis thaliana. In this study, we identified the MP gene from M. micrantha via orthologous gene analysis. A total of 37 MP orthologous genes was identified in 4 plants, including 9 MP candidate genes in M. micrantha, 13 in Helianthus annuus, 6 in Chrysanthemum nankingense, and 9 in Lactuca sativa. Phylogenetic analysis revealed that an MP candidate gene in M. micrantha (Mm01G000655, named MmMP) was clustered into one clade with the MP gene in A. thaliana (AtMP). In addition, both MmMP and AtMP contain a B3-DNA binding domain that is shared by transcription factors that regulate plant embryogenesis. To study gene function, dsRNA against MmMP (dsMmMP) was applied to the roots of M. micrantha. Compared with those of the controls, the expression of MmMP was reduced by 43.3%, 22.1%, and 26.2% on the first, third, and fifth days after dsMmMP treatment, respectively. The dsMmMP-treated plants presented several morphological defects, mostly in the roots. Compared with water-treated plants, the dsMmMP-treated plants presented reduced developmental parameters, including root length, number of adventitious roots, root fresh and dry weights, plant height, and aboveground biomass. Additionally, safety assessment suggested that this dsMmMP treatment did not silence MP genes from non-target plants, including rice and tomato; nor did it inhibit root growth in those species. Collectively, these results suggest that MmMP plays an important role in root development in M. micrantha and provides a potential target for the development of species-specific RNAi-based herbicides.

Why can Mikania micrantha cover trees quickly during invasion?

The invasion of Mikania micrantha by climbing and covering trees has rapidly caused the death of many shrubs and trees, seriously endangering forest biodiversity. In this study, M. micrantha seedlings were planted together with local tree species (Cryptocarya concinna) to simulate the process of M. micrantha climbing under the forest. We found that the upper part of the M. micrantha stem lost its support after climbing to the top of the tree, grew in a turning and creeping manner, and then grew branches rapidly to cover the tree canopy. Then, we simulated the branching process through turning treatment. We found that a large number of branches had been formed near the turning part of the M. micrantha stem (TP). Compared with the upper part of the main stem (UP), the contents of plant hormones (auxin, cytokinin, gibberellin), soluble sugars (sucrose, glucose, fructose) and trehalose-6-phosphate (T6P) were significantly accumulated at TP. Further combining the transcriptome data of different parts of the main stem under erect or turning treatment, a hypothetical regulation model to illustrate how M. micrantha can quickly cover trees was proposed based on the regulation of sugars and hormones on plant branching; that is, the lack of support after ascending the top of the tree led to turning growth of the main stem, and the enhancement of sugars and T6P levels in the TP may first drive the release of nearby dormant buds. Plant hormone accumulation may regulate the entrance of buds into sustained growth and maintain the elongation of branches together with sugars to successfully covering trees.

Can nanotechnology improve the application of bioherbicides?

Bioherbicides are composed of microorganisms or natural compounds and are used for weed control; however, they have specific weaknesses and constraints that hinder their development and success under field conditions. Nanotechnology can help to overcome these limitations by providing a good starting point for the design of specific formulations and carriers that minimize the deficiencies of natural compounds and microorganisms, such as low solubility, short shelf life or a loss of viability. In addition, nanoformulations can help to improve the efficacy of bioherbicides by increasing their effectiveness and bioavailability, reducing the amount required for a treatment, and enhancing their ability to target specific weeds while preserving the crop. However, it is important to choose the right materials and nanodevices depending on specific needs and considering several factors inherent to nanomaterials such as production cost, safety or possible toxic effects. © 2023 Society of Chemical Industry.

High-quality chromosome-level scaffolds of the plant bug Pachypeltis micranthus provide insights into the availability of Mikania micrantha control

BACKGROUND

The plant bug, Pachypeltis micranthus Mu et Liu (Hemiptera: Miridae), is an effective potential biological control agent for Mikania micrantha H.B.K. (Asteraceae; one of the most notorious invasive weeds worldwide). However, limited knowledge about this species hindered its practical application and research. Accordingly, sequencing the genome of this mirid bug holds great significance in controlling M. micrantha.

RESULTS

Here, 712.72 Mb high-quality chromosome-level scaffolds of P. micranthus were generated, of which 707.51 Mb (99.27%) of assembled sequences were anchored onto 15 chromosome-level scaffolds with contig N50 of 16.84 Mb. The P. micranthus genome had the highest GC content (42.43%) and the second highest proportion of repetitive sequences (375.82 Mb, 52.73%) than the three other mirid bugs (i.e., Apolygus lucorum, Cyrtorhinus lividipennis, and Nesidiocoris tenuis). Phylogenetic analysis showed that P. micranthus clustered with other mirid bugs and diverged from the common ancestor approximately 200 million years ago. Gene family expansion and/or contraction were analyzed, and significantly expanded gene families associated with P. micranthus feeding and adaptation to M. micrantha were manually identified. Compared with the whole body, transcriptome analysis of the salivary gland revealed that most of the upregulated genes were significantly associated with metabolism pathways and peptidase activity, particularly among cysteine peptidase, serine peptidase, and polygalacturonase; this could be one of the reasons for precisely and highly efficient feeding by the oligophagous bug P. micranthus on M. micrantha.

CONCLUSION

Collectively, this work provides a crucial chromosome-level scaffolds resource to study the evolutionary adaptation between mirid bug and their host. It is also helpful in searching for novel environment-friendly biological strategies to control M. micrantha.

RNA Interference Past and Future Applications in Plants

Antisense RNA was observed to elicit plant disease resistance and post-translational gene silencing (PTGS). The universal mechanism of RNA interference (RNAi) was shown to be induced by double-stranded RNA (dsRNA), an intermediate produced during virus replication. Plant viruses with a single-stranded positive-sense RNA genome have been instrumental in the discovery and characterization of systemic RNA silencing and suppression. An increasing number of applications for RNA silencing have emerged involving the exogenous application of dsRNA through spray-induced gene silencing (SIGS) that provides specificity and environmentally friendly options for crop protection and improvement.

Integrated Analysis of Transcriptome and Small RNAome Reveals the Regulatory Network for Rapid Growth in Mikania micrantha

M. micrantha has caused huge ecological damage and economic losses worldwide due to its rapid growth and serious invasion. However, the underlying molecular mechanisms of its rapid growth and environmental adaption remain unclear. Here, we performed transcriptome and small RNA sequencing with five tissues of M. micrantha to dissect miRNA-mediated regulation in M. micrantha. WGCNA and GO enrichment analysis of transcriptome identified the gene association patterns and potential key regulatory genes for plant growth in each tissue. The genes highly correlated with leaf and stem tissues were mainly involved in the chlorophyll synthesis, response to auxin, the CAM pathway and other photosynthesis-related processes, which promoted the fast growth of M. micrantha. Importantly, we identified 350 conserved and 192 novel miRNAs, many of which displayed differential expression patterns among tissues. PsRNA target prediction analysis uncovered target genes of both conserved and novel miRNAs, including GRFs and TCPs, which were essential for plant growth and development. Further analysis revealed that miRNAs contributed to the regulation of tissue-specific gene expression in M. micrantha, such as mmi-miR396 and mmi-miR319. Taken together, our study uncovered the miRNA-mRNA regulatory networks and the potential vital roles of miRNAs in modulating the rapid growth of M. micrantha.