How a single gene shapes leaf lobes in Brassica rapa
image: BrRCO negatively regulated BrACP5 to regulate leaf lobe formation. (a-b) VIGS-acp5 system within RcBr. qRT-PCR analysis of BrACP5 expression in VIGS system (a) and the phenotype of VIGS-acp5 plant. Lobe of first two true leaves mutating into rounded leaves (b). (c) Phenotype of RcBr under P(50+), P(100+) and P(−) conditions. Bars = 2 cm. (d) Root-associated APase activity in the RcBr background under P(−) and P(50+) conditions. Bars = 2 cm. (e) qRT-PCR analysis of BrACP5 expression under P(−) and P(50+) conditions, with three biological replicates. P(50+): Hoagland’s culture solution with 50 mg/L phosphorus; P(100+): Hoagland’s culture solution with 100 mg/L phosphorus; P(−): Hoagland’s culture solution with no extra phosphorus. Image link: https://academic.oup.com/view-large/figure/511821480/uhaf084f5.tif
Credit: Horticulture Research
Brassica crops, such as B. rapa, often display variations in leaf shape, including entire or lobed leaves, which significantly impact their adaptability and agricultural utility. Lobed leaves offer benefits such as increased wind resistance, drought tolerance, and space efficiency for mechanized planting. Genetic studies have revealed that the formation of leaf lobes is influenced by several genes, with one major locus on chromosome A10 in B. rapa being linked to this trait. However, the precise genetic players and mechanisms were not fully understood until now. Based on these challenges, further research is needed to uncover the full genetic regulation behind leaf morphology in Brassica crops.
Researchers from Shenyang Agricultural University and collaborators from Huazhong Agricultural University and the University of Western Australia have made significant strides in understanding the genetic underpinnings of leaf lobe formation in B. rapa. Published (DOI: 10.1093/hr/uhaf084) in Horticulture Research on March 12, 2025, their study pinpoints the BrRCO gene as a central regulator of leaf lobe formation, providing a new pathway for crop improvement.
The study begins with the fine-mapping of the lob10.1 locus, a major quantitative trait locus (QTL) previously identified in B. rapa for controlling leaf lobes. Researchers narrowed this region down to a 69.8 kb interval, which led to the discovery of BrRCO, an HD-ZIP I transcription factor. Through CRISPR/Cas9 gene editing and overexpression techniques, they confirmed that BrRCO functions as a negative regulator of BrACP5, a gene involved in phosphate metabolism. By binding directly to the BrACP5 promoter, BrRCO suppresses its expression, resulting in leaf lobe formation. This was further validated through mutant analysis and gene expression studies. The findings also suggest that BrRCO plays a role in controlling leaf shape through the phosphate-responsive pathway, a mechanism previously unexplored in this context.
"These findings highlight a pivotal genetic pathway that regulates a crucial agricultural trait in Brassica species," said Dr. Limin Hu, co-author of the study from Huazhong Agricultural University. "Understanding the role of BrRCO in leaf lobe formation not only deepens our knowledge of plant morphology but also opens new avenues for improving crop performance under varying environmental conditions."
The identification of BrRCO as a core gene for leaf lobe formation in B. rapa has profound implications for agricultural practices. By harnessing this genetic knowledge, breeders can develop Brassica varieties with optimized leaf shapes, improving plant density and resilience. Furthermore, the understanding of the phosphate-responsive pathway offers potential for enhancing plant growth in phosphorus-deficient soils, contributing to more sustainable farming practices. This research lays the groundwork for future crop improvement strategies aimed at enhancing yield and stress resistance in Brassica and other crops.
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References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhaf084
Funding information
This research was supported by the National Nature Science Foundation of China (31772296 and 31971976) and Hainan Seed Industry Laboratory (B22C49723).
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.