Tea plants fight back: Dual gene discovery boosts anthracnose resistance

Anthracnose, caused by the fungal pathogen Colletotrichum gloeosporioides, poses a major threat to global tea production. This study reveals that the transcription factor CsNAC17 enhances disease resistance in Camellia sinensis by directly activating the immune-related gene CsRPM1. Furthermore, another transcription factor, CsbHLH62, interacts with CsNAC17 to boost this regulatory function. Through gene overexpression and silencing assays in both tobacco and tea plants, researchers demonstrated that both factors play vital roles in mounting a hypersensitive response and reactive oxygen species accumulation, two hallmarks of plant immune defense. These findings offer novel genetic resources to enhance disease resistance in tea plants through breeding or biotechnology.

Anthracnose is a severe fungal disease that significantly reduces tea yield and quality, especially in warm and humid regions. Current management strategies rely heavily on chemical fungicides, raising concerns about sustainability and food safety. Recent research has shifted toward understanding plant immunity at the genetic level, especially focusing on resistance (R) genes such as NBS-LRR, which are critical for effector-triggered immunity (ETI). In particular, the RPM1 gene family has been found to initiate hypersensitive responses that halt pathogen spread. Based on these challenges, there is an urgent need to identify upstream transcriptional regulators and signaling pathways that could be leveraged to improve tea plant immunity.

A team of researchers from Nanjing Agricultural University published their findings (DOI: 10.1093/hr/uhae295) on October 14, 2024, in Horticulture Research, unveiling a molecular mechanism underlying anthracnose resistance in tea plants. Their study, titled “CsNAC17 enhances resistance to Colletotrichum gloeosporioides by interacting with CsbHLH62 in Camellia sinensis,” details how two transcription factors collaboratively regulate the expression of a key R gene, CsRPM1. This breakthrough provides valuable insight into the gene regulatory networks involved in disease resistance and offers promising targets for tea breeding programs.

The researchers began by comparing two tea cultivars, ‘Zhongcha108’ (resistant) and ‘Longjing43’ (susceptible), and observed elevated expression of CsNAC17 in the resistant line. Overexpression of CsNAC17 in both tobacco and tea leaves significantly reduced fungal lesion development and enhanced hypersensitive response (HR) and hydrogen peroxide (H₂O₂) accumulation. Using yeast two-hybrid (Y2H), bimolecular fluorescence complementation (BiFC), and co-immunoprecipitation assays, they found that CsNAC17 physically interacts with CsbHLH62, a basic helix-loop-helix transcription factor. While CsbHLH62 alone cannot activate CsRPM1, its interaction with CsNAC17 significantly amplifies CsRPM1’s promoter activity, as demonstrated by luciferase reporter assays and EMSA. Furthermore, silencing either CsNAC17 or CsbHLH62 reduced resistance, confirming their essential role. Notably, transient overexpression of CsRPM1 alone in susceptible ‘Longjing43’ leaves conferred stronger resistance and increased H₂O₂ accumulation, supporting its downstream position in the defense pathway. Together, these results outline a regulatory module where CsbHLH62 enhances CsNAC17’s activation of CsRPM1, leading to improved anthracnose resistance.

“Our findings highlight a novel transcriptional mechanism that plants use to resist anthracnose,” said Dr. Xinghui Li, senior author of the study. “By uncovering how CsNAC17 and CsbHLH62 work together to activate CsRPM1, we not only deepen our understanding of tea plant immunity but also provide actionable targets for genetic improvement. This research sets the stage for developing disease-resistant cultivars using gene editing or marker-assisted selection.”

The CsNAC17–CsbHLH62–CsRPM1 module offers promising opportunities for enhancing disease resistance in tea crops. These genes can be utilized in modern breeding programs aimed at improving plant immunity without relying on chemical treatments. Future research may explore whether similar transcriptional mechanisms are present in other crop species and how these pathways respond to multiple biotic stresses. Additionally, genome editing tools like CRISPR-Cas9 could be employed to optimize these genetic circuits in commercial tea cultivars. The integration of molecular genetics with traditional breeding stands to significantly improve both sustainability and productivity in global tea agriculture.

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References

DOI

10.1093/hr/uhae295

Original Source URL

https://doi.org/10.1093/hr/uhae295

Funding information

This work was supported financially by Key Research and Development Program of Jiangsu (BE2023364), National Key Research and Development Program of China (2022YFD1200505), Science and Technology Projects of Nanjing (202210013), Development of New Products from Summer and Autumn Tea in Wen County (2023), National Natural Science Foundation of China (32172628), Nanjing Agricultural Major Technology Collaborative Promotion Plan Project (2024NJXTTG 10) and Research and Demonstration Project of key technologies of tea garden photovoltaic power generation (HNKJ22- H135).

About Horticulture Research

Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.