Mustard (Brassica juncea), valued both as a vegetable and oilseed crop, faces constant threats from environmental stresses and insect pests. One natural defense lies in leaf trichomes, which serve as barriers against herbivores and help regulate water balance. However, the genetic regulation of trichome development in mustard has remained poorly understood compared to model plants like Arabidopsis thaliana. Previous studies pointed to structural variations in GL1-like genes but left gaps in explaining the full spectrum of trichome diversity. Based on these challenges, researchers sought to dissect the genetic basis of leaf hair formation in mustard and explore its role in enhancing pest resistance.
On February 1, 2025, a research team from Xinyang Normal University and Huazhong Agricultural University published (DOI: 10.1093/hr/uhae314) their findings in Horticulture Research. The study identifies two novel alleles of the MYB transcription factor genes, BjA06.GL1 and BjB02.GL1, that regulate leaf trichome development in mustard (Brassica juncea). Using a combination of genetic mapping, sequence analysis, and CRISPR/Cas9 editing, the researchers demonstrated that these genes not only drive trichome formation but also enhance the plant’s resistance to aphid infestation.
The scientists began by comparing mustard inbred lines with and without leaf trichomes, revealing that trichome traits are dominant but complex quantitative characteristics. Through QTL-seq mapping and gene function analysis, two candidate genes—BjA06.GL1 and BjB02.GL1—were pinpointed on chromosomes A06 and B02. Sequence comparisons showed key single-nucleotide polymorphisms and indels differentiating trichome-bearing lines from glabrous ones. Expression profiling confirmed that both genes were highly active in leaves with trichomes.
To validate their function, researchers used CRISPR/Cas9 technology to simultaneously knock out BjA06.GL1 and BjB02.GL1. The edited plants completely lost trichomes, producing smooth leaves. More strikingly, aphid infestation assays revealed that plants with trichomes harbored significantly fewer insects than glabrous mutants. This demonstrated a direct link between trichome presence and enhanced pest resistance.
Beyond pest defense, the study noted dynamic changes in trichome density during leaf growth and across plant tissues, suggesting a fine-tuned regulatory system. Together, the findings establish BjA06.GL1 and BjB02.GL1 as pivotal regulators of trichome development in mustard and highlight their importance in crop protection.
“Trichomes are much more than cosmetic traits in plants—they represent a vital line of defense,” said lead author Dr. Shuangping Heng of Xinyang Normal University. “By identifying and functionally validating BjA06.GL1 and BjB02.GL1, we have taken a major step toward understanding how mustard naturally resists aphids. The ability to manipulate these genes could allow breeders to enhance resistance in commercial varieties without relying heavily on pesticides. This work not only adds to basic plant science but also carries immediate significance for sustainable agriculture.”
The discovery of BjA06.GL1 and BjB02.GL1 provides valuable genetic resources for mustard breeding programs aimed at reducing crop losses to aphids. By incorporating these alleles into elite cultivars, plant breeders may develop varieties with enhanced natural resistance, thereby lowering pesticide use and production costs. This approach aligns with global efforts to promote environmentally sustainable agriculture while safeguarding food security. Moreover, insights from mustard may extend to other Brassicaceae crops, offering a broader impact on vegetable and oilseed improvement. Future research will explore how these genes interact with other regulatory networks to refine trichome-based defenses.
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References
DOI
10.1093/hr/uhae314
Original Source URL
https://doi.org/10.1093/hr/uhae314
Funding information
This research was supported by grants from the National Natural Science Foundation of China (32002056), the training program for young backbone teachers in Henan Province (2024GGJS085), the Natural Science Foundation of Henan Province (232300420021), and the Nanhu Scholars Program for Young Scholars of XYNU.
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.