Stem trichome polarity development in Gossypium hirsutum: insights into GhPRP gene regulation.

Key message: Cotton stem trichomes exhibit a distinct polarity distribution, which may be regulated by GhPRP genes and temperature. Stem trichomes in cotton are essential for pest resistance and stress tolerance, yet their molecular regulation remains poorly understood. Significant differences in trichome number and length were observed under 25 °C and 30 °C, with more and longer trichomes at the first stem node under 25 °C. The side above the first true leaf (M side) showed more number of trichomes than the opposite side (L side), indicating polarity distribution. Transcriptome sequencing (RNA-seq) identified differentially expressed genes (DEGs), and 17 key DEGs were selected for further analysis, including 9 upregulated genes encoding proline-rich cell wall proteins (PRPs), flavonol synthase (FLS), prolyl endopeptidase (PREP), and diacylglycerol O-acyltransferase 3 (DGAT3). Quantitative real-time PCR (qRT-PCR) confirmed higher GhPRP expression on the M side. When GhPRP1, GhPRP2, or GhPRP10 was silenced using virus-induced gene silencing (VIGS) technique, trichome density decreased, and polarity was disrupted, highlighting their regulatory roles. Bioinformatics analysis revealed hormone signal transduction-related domains in PRP gene promoters, potentially linking them to trichome polarity regulation. This study advances understanding the mechanisms of trichome polarity distribution and offers insights for improving pest resistance and stress adaptation in cotton.