Abstract
BACKGROUND: Tobacco brown spot disease, caused by the fungus Alternaria alternata, is a significant threat to global crop production, including in China. Our previous research identified NaLRR-RK4 as a key gene conferring resistance to this disease in wild tobacco (Nicotiana attenuata). In agricultural practice, the incidence of tobacco brown spot disease varies significantly with nitrogen levels, with plants under high nitrogen conditions exhibiting more severe symptoms. However, the relationship between nitrogen nutrition and the function of the homologous gene (NtLRR-RK4) in cultivated tobacco remains unknown. RESULTS: This study investigated the interaction between nitrogen levels and disease resistance in two cultivated tobacco varieties (N. tabacum), K326 and Hongda (HD). Tobacco plants were subjected to low, medium, and high nitrogen fertilizer levels and inoculated with A. alternata. Using RNA silencing and nitrogen treatments, we found that during infection, expression of the NtLRR-RK4 gene, along with its downstream targets NtERF109, NtDEF19, and the key scopoletin phytoalexin synthase gene NtF6'H1, was significantly higher in low nitrogen plants than in high nitrogen plants. Furthermore, under identical nitrogen conditions, gene expression was consistently higher in the K326 variety than in HD. Subsequent analysis revealed that nitrogen levels directly influence the NtLRR-RK4-mediated defense response. Specifically, high nitrogen input suppressed the activity of antioxidant enzymes (catalase, peroxidase and superoxide dismutase) and reduced flavonoid biosynthesis. This suppression was more pronounced in HD, resulting in greater susceptibility to A. alternata compared with K326. CONCLUSION: In summary, we demonstrate for the first time that the disease resistance conferred by NtLRR-RK4 is modulated by nitrogen availability and host genetic factors. Overall, these results provide new insights into the molecular mechanisms of brown spot resistance in tobacco, informing the development of effective control strategies. © 2026 Society of Chemical Industry.
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Claims 6
Claim · model-written summary
During infection, low nitrogen tobacco had higher NtLRR-RK4 and downstream defense gene expression than high nitrogen tobacco.
- Taxon
- tobacco
Nicotiana tabacumt0 - Treatment
- low nitrogene0
- Interactor
- Alternaria alternata
.jpg?width=60)
Alternaria alternatat0pathogen - Gene
- NtLRR-RK4e0
- Outcome
- expressione0
- Direction
- highere0
- Comparator
- high nitrogene0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“during infection, expression of the NtLRR-RK4 gene, along with its downstream targets NtERF109, NtDEF19, and the key scopoletin phytoalexin synthase gene NtF6'H1, was significantly higher in low nitrogen plants than in high nitrogen plants”
t0“Alternaria alternata in flue‐cured tobacco”
Claim · model-written summary
At the same nitrogen level, K326 had higher defense gene expression than HD.
- Taxon
- tobaccoNicotiana tabacumt0
- Material
- K326e0
- Outcome
- gene expressione0
- Direction
- highere0
- Comparator
- HDe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“under identical nitrogen conditions, gene expression was consistently higher in the K326 variety than in HD”
t0“tobacco”
Claim · model-written summary
High nitrogen suppressed antioxidant enzyme activity in tobacco.
- Taxon
- tobaccoNicotiana tabacumt0
- Treatment
- high nitrogen inpute0
- Outcome
- activity of antioxidant enzymese0
- Direction
- suppressede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“high nitrogen input suppressed the activity of antioxidant enzymes (catalase, peroxidase and superoxide dismutase)”
t0“tobacco”
Claim · model-written summary
High nitrogen reduced tobacco flavonoid biosynthesis.
- Taxon
- tobaccoNicotiana tabacumt0
- Treatment
- high nitrogen inpute0
- Outcome
- flavonoid biosynthesise0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“high nitrogen input suppressed the activity of antioxidant enzymes (catalase, peroxidase and superoxide dismutase) and reduced flavonoid biosynthesis”
t0“tobacco”
Claim · model-written summary
High nitrogen suppression was more pronounced in HD than K326, and HD was more susceptible to A. alternata.
- Taxon
- tobaccoNicotiana tabacumt0
- Material
- HDe0
- Interactor
- A. alternataAlternaria alternatae0pathogen
- Outcome
- susceptibility to A. alternatae0
- Direction
- greatere0
- Comparator
- K326e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This suppression was more pronounced in HD, resulting in greater susceptibility to A. alternata compared with K326”
t0“tobacco”
Claim · model-written summary
NtLRR-RK4-conferred resistance was modulated by nitrogen availability and host genetic factors.
- Taxon
- tobaccoNicotiana tabacumt0
- Gene
- NtLRR-RK4e0
- Outcome
- disease resistancee0
- Qualifier
- nitrogen availability and host genetic factorse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the disease resistance conferred by NtLRR-RK4 is modulated by nitrogen availability and host genetic factors”
t0“tobacco”
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