A research team led by Dr. Xuewei Chen from Sichuan Agricultural University has developed a genetic strategy to enhance broad-spectrum disease resistance in rice without compromising plant growth and yield, a major challenge in crop breeding. The findings are published in The Crop Journal .
Rice, a staple food for half of the global population, is constantly threatened by diseases such as rice blast, bacterial blight, and sheath blight. While lesion mimic mutant ( LMM ) genes are known to confer broad-spectrum disease resistance, their constitutive activation often triggers autoimmunity that stunts plant growth and reduces yield. Additionally, traditional resistance genes (e.g., NLRs ) provide only race-specific protection that is overcome by rapidly evolving pathogens, and many defense regulators exhibit pleiotropic effects on growth.
To address these issues, the research team targeted the AAA-type ATPase gene LRD6-6 , a rice LMM gene that suppresses plant immunity via the multivesicular body (MVB)-mediated vesicle trafficking pathway. They first identified a dominant-negative (DN) variant of this gene, LRD6-6 E315Q , whose constitutive expression strongly enhanced resistance to multiple rice pathogens but significantly impaired agronomic trait.
The main finding was the identification of a rare pathogen-inducible promoter, MIG6P , through a genome-wide expression screen of early-stage rice-blast fungus interactions. MIG6P exhibits three properties: extremely low basal activity under normal growing conditions, rapid and specific activation within 6 hours of pathogen infection, and no induction by abiotic stresses (high temperature, drought, salt) — an advantage over previously reported inducible promoters that are either pathogen-specific or responsive to environmental stress.
The team then constructed a gene expression cassette, MIG6P:LRD6-6 E315Q , by driving the DN variant LRD6-6 E315Q with the MIG6P promoter, and introduced it into the rice cultivar Taipei 309 (TP309). The engineered rice lines carrying this cassette showed no abnormal growth or yield loss under pathogen-free conditions, matching the agronomic performance of wild-type TP309. When challenged by pathogens, however, MIG6P was rapidly activated, driving the expression of LRD6-6 E315Q to trigger an immune response.
Further tests confirmed that the engineered rice lines exhibited enhanced broad-spectrum resistance to rice blast (caused by Magnaporthe oryzae ), bacterial blight ( Xanthomonas oryzae pv. oryzae ), and sheath blight ( Rhizoctonia solani ). Notably, in natural rice blast nurseries over two consecutive years, the transgenic lines had significantly lower panicle blast rates and higher grain yields compared to wild-type TP309, effectively breaking the resistance-yield trade-off.
"Our work provides a novel approach to utilize LMM genes for crop disease resistance without yield penalties," said first author Dr. Xiaobo Zhu. "By coupling a pathogen-specific inducible promoter with a DN LMM variant, we ensure that the immune response is only activated when needed, at the early stage of pathogen invasion, and shuts down once the pathogen threat is contained, allowing normal plant growth and maximum yield potential."
"The MIG6P promoter is a valuable genetic tool for driving the expression of defense-related genes, and the conserved DN effect of LRD6-6 homologs means this approach can be adapted to improve disease resistance of diverse crops to different fungus and bacterial pathogens, reducing reliance on chemical pesticides and securing global food production," adds corresponding author Dr. Xuewei Chen.
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Contact the author:
Guangming Yang
Email address: yangguangming@caas.cn
Tel: 13683670916
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The Crop Journal
Experimental study
Not applicable
Pathogen-inducible gene LRD6-6E315Q breaks the trade-off between disease resistance and yield in rice
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.