Strengthening crop stems: New insights from pepper plant genetics
Nanjing Agricultural University The Academy of Science
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CaSLR1 regulates the expression of cellulose, hemicellulose, and lignin biosynthesis related genes in pepper stems. (a) The expression-related heatmap of genes involved in the cellulose biosynthesis pathway and cell wall structural proteins. (b) The expression-related heatmap of genes involved in the hemicellulose biosynthesis pathway. (c) The expression-related heatmap of genes involved in the lignin biosynthesis pathway. (d) qRT-PCR analysis verified the down-regulated genes related to SCW formation pathways using RNA-seq. The results were expressed as the mean ± SE (n = 3). **P < 0.01; ***P < 0.001, as determined by the Student's t-test. (e) A hypothesis suggests that CaSLR1 regulated the stem lodging resistance. In WT, CaNAC6 binds to SNBE elements in the promoter of CaSLR1, thereby inducing its transcription. As a result, the stem accumulated cellulose, hemicellulose, and lignin, which promotes the deposition of the SCW and increases stem strength, enabling the stem remain upright. In contrast, in the mutant slr1, a deletion of CaSLR1 and its promoter abolished the binding of CaNAC6 to the SNBEs. The transcription of CaSLR1 was inhibited, and the accumulation of cellulose, hemicellulose, and lignin in stems was reduced. Accordingly, it resulted in the thinning of the SCW, weakening of stem strength, and finally, stem lodging. ‘×’ marked that the effect was cancelled. CESA: cellulose synthase; COBL4: COBRA-like 4; IRX9: irregular xylem 9; XTH30: xyloglucan endotransglucosylase protein 30; CCoAOMTL: caffeoyl-CoA O-methyltransferase 1ike; laccase 2 L: laccase 2-like; 4CL1: 4-coumarate-Co-A ligase 1; CAD1: cinnamyl alcohol dehydrogenase 1; 4CCL7: 4-coumarate-Co-A ligase like 7; AAE2: Acyl-activating enzyme 2; ACSL4: Long chain acyl-CoA synthetase 4-like; IRX15LL: IRX15 − LIKE − like.
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A recent study has identified CaSLR1, a gene in pepper plants, as a key regulator of stem strength by controlling cell wall development. This discovery offers significant potential for agriculture, paving the way for breeding crops with enhanced resistance to lodging. Such improvements can lead to increased yield stability and reduced production costs, providing substantial benefits for farmers.
Stem lodging is a major challenge in agricultural production, especially in crops like peppers with heavy above-ground biomass. Lodging reduces stem strength and stability, severely affecting crop yield and quality. Research has shown that cell wall components—cellulose, hemicellulose, and lignin—are crucial for structural support. However, the genetic mechanisms behind stem lodging in the Solanaceae family remain largely unknown, highlighting the urgent need for deeper exploration into the genes that regulate stem strength and lodging resistance.
Scientists from Hunan Agricultural University have pinpointed a gene linked to stem strength in Capsicum annuum, as reported (DOI: 10.1093/hr/uhae169) in Horticulture Research on June 20, 2024. The study zeroes in on CaSLR1, a MYB family transcription factor identified through genetic analysis of a pepper mutant prone to lodging. The findings reveal that CaSLR1 plays a crucial role in regulating cell wall biosynthesis, thereby enhancing stem strength and minimizing lodging. The gene's function was validated in both pepper and tomato, demonstrating its broader relevance in promoting stem stability.
The research identified CaSLR1 through analysis of a stem lodging-resistant pepper mutant, showing that this MYB transcription factor is essential for secondary cell wall formation. Silencing CaSLR1 led to a significant decrease in cell wall thickness and stem strength, with similar outcomes observed in tomatoes when the homologous gene SlMYB61 was disrupted. Further analysis revealed that CaNAC6, a gene involved in cell wall formation, positively regulates CaSLR1 expression. Experimental validation confirmed that CaNAC6 binds to the CaSLR1 promoter, highlighting the importance of the CaNAC6-CaSLR1 module in maintaining stem integrity. This research advances our understanding of stem development and offers new targets for breeding resilient crops.
Dr. Xuexiao Zou, a lead researcher on the study, noted, “This discovery uncovers a critical genetic factor in the battle against stem lodging in peppers. By understanding how CaSLR1 regulates cell wall biosynthesis, we can develop precise breeding strategies to strengthen stems and boost crop yield. Our findings not only enhance plant genetic knowledge but also hold significant promise for sustainable agriculture.”
The discovery of CaSLR1's role in enhancing stem strength opens new opportunities for breeding programs aimed at improving lodging resistance in peppers and tomatoes. By focusing on this gene, breeders can develop varieties that minimize stem breakage, reducing yield losses and boosting overall productivity. Furthermore, insights into the genetic pathways regulating stem strength can inform strategies for enhancing resilience in other crops, contributing to more sustainable and stable agricultural practices in response to environmental challenges.
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References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhae169
Funding information
This research was supported by the National Natural Science Foundation of China (32172584), the Natural Science Foundation of Hunan Province (2021JJ30339), the Hunan Provincial Innovation Foundation for Postgraduate (CX20200655), and the National Natural Science Foundation of China (32002040).
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number two 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.
Journal
Horticulture Research
Subject of Research
Not applicable
Article Title
Stem lodging Resistance-1 controls stem strength by positively regulating the biosynthesis of cell wall components in Capsicum annuum L.
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