Trichomes\u2014tiny hair\u2011like structures on leaves\u2014serve as physical barriers that protect plants from insect herbivores, UV radiation, excessive water loss, and toxic chemicals. They also contribute to stress tolerance and, in some crops, influence nutritional quality. In Arabidopsis, trichome development is governed by a well\u2011characterized regulatory network involving transcription factors and cell\u2011cycle regulators. However, in wucai, a Brassica vegetable prized for its rich glucosinolates and amino acids, most commercial cultivars are low\u2011density or completely glabrous. The genetic basis for this trait loss has remained unknown. Based on these challenges, there is a need to conduct in\u2011depth research on the genetic and molecular mechanisms underlying trichome loss in wucai.<\/p>\n
A study published (DOI: 10.1093\/hr\/uhag184)<\/a> on May 8, 2026, in Horticulture Research<\/a>\u2014a journal of Nanjing Agricultural University\u2014reports the identification of a transposon insertion that disrupts trichome formation in wucai (Brassica campestris L.). The research was conducted by scientists from Anhui Agricultural University’s School of Horticulture in Hefei, China. Using a combination of bulked segregant analysis sequencing (BSA\u2011seq) and map\u2011based cloning, the team pinpointed BcCPR5 \u2014the wucai homolog of Arabidopsis CPR5 (Constitutive Pathogen Response5)\u2014as the key gene controlling trichome density.<\/p>\n The researchers compared two wucai inbred lines: W7\u20111, which is densely hairy, and W7\u20112, which is largely hairless except for a few trichomes along leaf margins. Genetic analysis showed that the trait is controlled by a single dominant nuclear gene, with a 3:1 segregation ratio in the F2 population. Through progressive fine\u2011mapping, they narrowed the candidate region to a 114\u2011kb interval on chromosome A06 and identified BcCPR5 as the causal gene.<\/p>\n The key difference between the two lines turned out to be a 3,365\u2011base\u2011pair transposon insertion in the BcCPR5 promoter of W7\u20112. This insertion reduced promoter activity by more than 80%, slashing BcCPR5 expression. Virus\u2011induced gene silencing (VIGS) of BcCPR5 in the hairy line dropped trichome density to one\u2011sixth of normal levels, confirming the gene’s essential role. The team further discovered that the transcription factor BcWRKY44 directly activates BcCPR5 by binding to a W\u2011box element in its promoter. In W7\u20112, the transposon insertion physically separates this W\u2011box from the transcription start site, blocking activation. Notably, coding\u2011sequence differences between the two lines\u2014including a 43\u2011bp deletion and multiple amino\u2011acid changes\u2014did not affect BcCPR5 function, ruling out protein\u2011level defects as the cause.<\/p>\n “The transposon insertion basically cuts the communication line between the activator and the gene,” the authors said. “BcWRKY44 can still bind to the promoter, but the insertion puts a physical barrier between the binding site and the transcription start site, so activation never reaches the gene. What surprised us most was that such a modest reduction in overall transcript level\u2014about 40% in whole leaves\u2014could have such a dramatic effect on trichome density. We think BcCPR5 is expressed specifically in trichome cells, so the actual suppression there is much stronger than what whole\u2011leaf measurements suggest.”<\/p>\n The 3,365\u2011bp insertion was found in 27.6% of low\u2011density wucai inbred lines and 36.7% of glabrous pakchoi accessions, but absent from all high\u2011density lines, suggesting it has been selected during domestication and breeding. The study’s findings offer a clear molecular target for breeding wucai varieties with optimized trichome density\u2014balancing the need for pest resistance against consumer preferences for smooth, easy\u2011to\u2011harvest leaves. The BcWRKY44\u2011 BcCPR5 module also provides a conserved framework for understanding trichome regulation across Brassica crops. Looking forward, the team plans to use metabolomics to explore whether high\u2011density trichomes contribute to nutritional quality, as seen in tea plants where trichomes accumulate valuable flavor compounds.<\/p>\n ###<\/p>\n References<\/p>\n DOI<\/p>\n 10.1093\/hr\/uhag184<\/a><\/p>\n Original Source URL<\/p>\n https:\/\/doi.org\/10.1093\/hr\/uhag184<\/a><\/p>\n Funding information<\/p>\n Provincial Key Development Program for Basic Research of Anhui (2023z04020005), Natural Science Foundations of Anhui Province (2308085QC101), National Natural Science Foundation of China (32472735; 32272703).<\/p>\n