The Regulatory Role of R2R3-MYB Family Genes in Trichome Formation in Solanum aculeatissimum

Solanum aculeatissimum is a medicinally and economically significant crop characterized by its aerial organs, which are densely covered with trichomes and spines. Trichomes serve as crucial sites for the synthesis of secondary metabolites in medicinal plants and represent important structural adaptations for resisting biotic and abiotic stresses. Elucidating the molecular mechanisms underlying trichome formation in S. aculeatissimum holds significant implications for enhancing both its medicinal value and stress resistance. The R2R3-MYB subfamily, the largest within the MYB transcription factor family, plays a pivotal role in regulating trichome development. Here, we present the first genome-wide identification of the R2R3-MYB gene family in S. aculeatissimum, characterizing 99 members. Phylogenetic analysis classified these SaMYBs into 10 groups. Cis-element predictions in their promoter regions revealed an abundance of light-responsive, phytohormone-responsive, and abiotic stress-responsive elements, suggesting roles in environmental adaptation. Furthermore, synteny analysis identified 25 segmentally duplicated gene pairs, and the purifying selection has been the dominant evolutionary force. Through comparative transcriptomic analysis of leaves from wild-type and sparse-trichome plants, we identified 16 differentially expressed SaMYB genes, comprising 3 upregulated and 13 downregulated genes. Subsequent qRT-PCR analysis showed that SaMYB1, SaMYB59, and SaMYB36 were highly expressed during early leaf development. Virus-induced gene silencing (VIGS) targeting these candidates demonstrated that silencing SaMYB59 significantly reduced trichome density, whereas silencing SaMYB1 or SaMYB36 produced no observable phenotypic change, confirming SaMYB59 as a key positive regulator of trichome formation. Our findings provide crucial molecular targets for elucidating the mechanisms of trichome development in S. aculeatissimum and establish a theoretical foundation for genetic improvement of this medicinal plant through regulation of the SaMYB59 gene.