Exploring the jasmonic acid signaling pathway: the role of CsAOS in modulating Trichome density in cucumber

Abstract Jasmonic acid (JA) and its derivatives, including methyl jasmonate, are well-known plant growth regulators that mediate a wide range of physiological and developmental processes. Although the role of JA in regulating fruit trichome density has been recognized, but the specific mechanisms underlying this remain to be fully understood. This study investigated the effects of various JA concentrations on trichome density at different developmental stages in cucumber (Cucumis sativus L.). Our findings revealed a dose-dependent increase in trichome density following exogenous JA application, with 1.5 mM JA showing the most significant effect at all stages. Conversely, the use of a JA biosynthesis inhibitor resulted in reduced trichome density, further highlighting the pivotal role of JA in trichome formation. Through transcriptomic analysis, we identified the Allene oxide synthase CsAOS gene, which encodes an allene oxide synthase, as a key regulator of JA biosynthesis enzyme preferentially expressed in trichomes. To investigate its functional role, we used CRISPR/Cas9-mediated knockout and overexpression strategies. Knockout of CsAOS in wild-type plants leads to a significant reduction in trichome density, whereas CsAOS overexpression in wild-type plants results in an enhanced trichome phenotype. These results provide novel insights into the molecular mechanisms governing trichome development in cucumbers, establishing CsAOS as a critical mediator of JA signaling in regulating trichome density. This study not only sheds light on the intricate relationship between JA and trichome development but also paves the way for future applications in plant breeding and genetic modification to improve pest resistance and herbivore defense.