“The Circular Dance of Resilience: Unraveling the Regulatory Roles of circRNAs in Abiotic Stress Tolerance of Soybean”


Soybean (Glycine max) stands as one of the world’s foremost crops, contributing significantly to global food and protein production. However, the agricultural landscape is continually challenged by various abiotic stresses, including drought, salinity, and extreme temperatures, which compromise soybean yield and quality. In the face of these challenges, understanding the molecular mechanisms that govern stress responses and tolerance in soybean is paramount for developing resilient cultivars that can thrive under adverse environmental conditions.

The last decade has witnessed a burgeoning interest in non-coding RNAs (ncRNAs) as crucial players in the regulation of gene expression and cellular processes. Among these, circular RNAs (circRNAs) have emerged as a distinctive class of ncRNAs characterized by a covalently closed loop structure. Initially considered as byproducts of splicing errors, circRNAs are now recognized for their diverse and intricate roles in gene regulation, including the modulation of stress responses in plants.

Abiotic Stress in Soybean:

  • Drought:
    • Drought stress is a pervasive threat to soybean production, especially in regions with irregular rainfall patterns.
    • Water deficiency hampers physiological processes, such as photosynthesis and nutrient uptake, leading to reduced growth and yield.
    • Drought stress during critical developmental stages, such as flowering and pod filling, can result in significant yield losses.
  • Salinity:
    • Soil salinity is a growing concern in many soybean-growing areas due to irrigation practices and natural soil conditions.
    • Elevated salt levels impede water uptake by plant roots and disrupt ion balance, causing osmotic stress and ion toxicity.
    • Salinity stress negatively impacts soybean growth, affecting germination, seedling establishment, and overall plant health.

Circular RNAs: Biogenesis and Functions:

  • Exonuclease Resistance:
    • Circularization of RNA molecules occurs during pre-mRNA splicing, where a splice donor site joins a splice acceptor site in a reverse order, creating a circular structure.
    • This back-splicing process is facilitated by the cooperation of various RNA-binding proteins and the presence of complementary sequences in flanking introns.
  • Intron-pairing-driven Circularization:
    • Introns flanking exons harboring circRNAs often contain complementary sequences that facilitate circularization through base-pairing interactions.
    • The formation of RNA secondary structures, such as RNA-RNA bridges, promotes back-splicing.

Circular RNAs: Biogenesis and Functions:

Circular RNAs (circRNAs) represent a fascinating class of non-coding RNAs characterized by a covalently closed loop structure, setting them apart from traditional linear RNAs. This unique structure renders circRNAs resistant to exonuclease degradation, providing increased stability and often contributing to their diverse functions. The biogenesis of circRNAs primarily occurs through a process known as back-splicing, in which a downstream 5′ splice site is ligated to an upstream 3′ splice site, forming a circular configuration. The biogenesis of circRNAs involves several mechanisms:

1. Exonuclease Resistance:

  • Circularization takes place during pre-mRNA splicing.
  • A splice donor site joins a splice acceptor site in reverse order, creating a closed-loop structure.
  • This back-splicing process is facilitated by RNA-binding proteins and specific sequence motifs in flanking introns.

2. Intron-pairing-driven Circularization:

  • Complementary sequences in introns flanking exons containing circRNAs promote circularization through base-pairing interactions.
  • RNA secondary structures, like RNA-RNA bridges, contribute to the stabilization of circRNAs.

Identification and Profiling of CircRNAs in Soybean:

The exploration of circular RNAs (circRNAs) in soybean involves a multi-faceted approach, combining experimental and computational methodologies. Identifying and profiling circRNAs is crucial for understanding their expression patterns, potential functions, and their roles in abiotic stress responses. Here is an overview of the methods employed in the identification and profiling of circRNAs in soybean:

1. High-Throughput RNA Sequencing (RNA-Seq):

  • Library Construction: RNA extracted from soybean tissues under normal and stress conditions is used to construct RNA-seq libraries.
  • rRNA Depletion: To enrich for non-coding RNAs, ribosomal RNA (rRNA) is often depleted from the total RNA sample.
  • Library Sequencing: High-throughput sequencing of the libraries generates vast amounts of short RNA reads.

Regulatory Roles of CircRNAs in Abiotic Stress Tolerance in Soybean:

Understanding the regulatory roles of circular RNAs (circRNAs) in abiotic stress tolerance of soybean involves unraveling the intricate mechanisms through which circRNAs influence gene expression and cellular processes. Here, we explore specific examples and potential regulatory functions of circRNAs in mitigating the impact of abiotic stresses.

  • Mechanism: CircRNAs can act as competitive endogenous RNAs (ceRNAs) by sponging microRNAs (miRNAs).
  • Functional Impact: By sequestering miRNAs, circRNAs may relieve the repression of target mRNAs, leading to enhanced stress tolerance.
  • Example: A soybean circRNA might sponge a stress-responsive miRNA, indirectly regulating the expression of stress-related genes.

Challenges and Limitations in Studying CircRNAs in Soybean Abiotic Stress Tolerance:

While the study of circular RNAs (circRNAs) in the context of abiotic stress tolerance in soybean holds great promise, it also comes with several challenges and limitations that researchers need to address. Here are some of the key challenges faced in this field:

  • Annotation and Genome Assembly:
    • Challenge: The accurate identification and annotation of circRNAs rely on the completeness and accuracy of the soybean genome assembly.
    • Limitation: Incomplete or inaccurate genome assemblies may lead to misidentification of circRNAs or the omission of important regulatory elements.
  • Low Abundance and Tissue-Specific Expression:
    • Challenge: CircRNAs often exhibit lower abundance compared to linear RNAs, making their detection challenging.
    • Limitation: Tissue-specific expression patterns may result in some circRNAs being overlooked in studies that focus on specific tissues, developmental stages, or stress conditions.


In conclusion, the exploration of circular RNAs (circRNAs) in the context of abiotic stress tolerance in soybean represents a burgeoning field with vast potential for enhancing our understanding of plant stress responses. As soybean cultivation faces increasing challenges due to climate variability, deciphering the regulatory roles of circRNAs offers novel insights into the molecular mechanisms governing stress adaptation. This review has traversed the intricate landscape of circRNAs in soybean, highlighting their biogenesis, functions, and specific contributions to abiotic stress tolerance.

The biogenesis of circRNAs, characterized by exonuclease resistance and intricate splicing mechanisms, underscores their stability and potential as key players in stress-responsive gene regulation. Their diverse functions, ranging from miRNA sponging to protein interaction, emphasize the multifaceted roles circRNAs play in shaping cellular processes under adverse conditions.

Identification and profiling of circRNAs in soybean, facilitated by high-throughput RNA sequencing and computational analysis, have paved the way for cataloging these molecules. Experimental validation techniques, such as RT-PCR, provide a foundation for confirming the existence of circRNAs and elucidating their expression patterns in response to abiotic stresses.

Moreover, the regulatory roles of circRNAs in abiotic stress tolerance are emerging as crucial components of the soybean stress response toolkit. Examples of circRNAs acting as miRNA sponges, modulating protein interactions, and influencing signaling pathways underscore their significance in orchestrating adaptive responses.

However, this journey is not without challenges. The accurate annotation of circRNAs, their low abundance, and the need for robust validation techniques present hurdles in unraveling their complete regulatory network. Functional annotation and a deeper mechanistic understanding of circRNA actions in soybean stress tolerance will require concerted efforts and interdisciplinary approaches.

As we navigate these challenges, the potential applications of circRNA research in soybean breeding and genetic engineering become apparent. Harnessing the knowledge of circRNAs could pave the way for developing stress-resistant soybean varieties, contributing to sustainable agriculture and food security in the face of a changing climate.

In essence, the study of circRNAs in soybean abiotic stress tolerance is an exciting frontier that holds promise for transforming our approaches to crop improvement. By continuing to explore, validate, and understand the intricate roles of circRNAs, researchers can contribute to the development of resilient soybean varieties capable of thriving in the face of environmental challenges.

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