How Apple Fights Off Fungal Infections by Boosting Lignin Production

Jenn Hoskins
10th June, 2024

How Apple Fights Off Fungal Infections by Boosting Lignin Production

Image Source: Natural Science News, 2024

Key Findings

  • Researchers at Shenyang Agricultural University, China, found that salicylic acid (SA) boosts apple resistance to the fungal pathogen Colletorichum gloeosporioides
  • The study identified a transcription factor, MdMYB46, which increases lignin accumulation, strengthening apple cell walls and enhancing disease resistance
  • SA reduces the expression of miR7125, allowing higher levels of MdARF1, which in turn upregulates MdMYB46, leading to improved apple resistance
Apple, a crucial cash crop in China, faces significant challenges from fungal infections, particularly apple bitter rot caused by Colletorichum gloeosporioides. This disease can severely impact apple yield. Recent research from Shenyang Agricultural University, China, has provided new insights into the molecular mechanisms that enhance apple resistance to this pathogen[1]. This study focuses on the role of salicylic acid (SA) in disease resistance and its interaction with lignin synthesis pathways. Salicylic acid is well-known for its role in plant defense mechanisms. It activates specific pathways that help plants resist pathogens. Previous studies have shown that SA can inhibit ethylene production, which is often associated with stress responses in plants. For instance, in sweet pepper, SA was found to suppress ethylene evolution under salinity stress, thereby improving germination and growth[2]. This ability of SA to modulate stress responses is crucial in understanding its broader role in plant immunity. In the context of apple, the study identified a key transcription factor, MdMYB46, which promotes lignin accumulation—a critical component for reinforcing cell walls and enhancing disease resistance. Overexpression of MdMYB46 was shown to significantly improve apple's resistance to C. gloeosporioides. This finding aligns with earlier research indicating that lignin synthesis is a vital part of the plant's defense strategy against various stresses, including salinity and osmotic stress. The research also delved into the upstream regulatory mechanisms controlling MdMYB46. Through yeast library screening, the researchers identified another transcription factor, MdARF1, which regulates MdMYB46. Further analysis revealed that MdARF1 is negatively regulated by miR7125, a microRNA whose expression is influenced by SA signals. This regulatory pathway was confirmed through luciferase (LUC) assays and quantitative real-time PCR (qRT-PCR), demonstrating that higher levels of SA lead to decreased miR7125 expression, thereby allowing greater expression of MdARF1 and subsequent upregulation of MdMYB46. This study is significant because it elucidates a new pathway where SA signals contribute to lignin accumulation, thereby enhancing disease resistance in apples. It expands on previous findings by integrating the role of SA in stress responses and its impact on lignin synthesis, a crucial aspect of plant structural integrity and defense. For example, in Arabidopsis, SA was shown to activate defense genes via NPR1-dependent and independent pathways, highlighting its versatile role in plant immunity[3]. Similarly, the apple study shows that SA not only triggers defense responses but also modulates key transcription factors and microRNAs that lead to lignin accumulation. Moreover, the identification of miR7125 as a regulator provides a deeper understanding of how plants fine-tune their defense mechanisms at the molecular level. This microRNA's response to SA signals adds another layer of complexity to the plant's immune response, akin to the sophisticated regulatory networks observed in other plants' defense pathways[4]. In summary, the findings from Shenyang Agricultural University offer valuable insights into the molecular mechanisms by which SA enhances disease resistance in apples. By elucidating the role of MdMYB46 and its upstream regulators, this study provides a foundation for future research aimed at breeding disease-resistant apple varieties. These insights not only advance our understanding of plant immunity but also have practical implications for improving crop resilience against fungal pathogens.

GeneticsBiochemPlant Science

References

Main Study

1) The miR7125-MdARF1 module enhances the resistance of apple to Colletotrichum gloeosporioides by promoting lignin synthesis in response to salicylic acid signalling.

Published 9th June, 2024

https://doi.org/10.1111/pbi.14401

Related Studies

2) Role of salicylic acid in regulating ethylene and physiological characteristics for alleviating salinity stress on germination, growth and yield of sweet pepper.

https://doi.org/10.7717/peerj.8475

3) Early genomic responses to salicylic acid in Arabidopsis.

https://doi.org/10.1007/s11103-009-9458-1

4) Plants send small RNAs in extracellular vesicles to fungal pathogen to silence virulence genes.

https://doi.org/10.1126/science.aar4142


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