SlHDZIV8-SlnsLTP33 module controls trichome density and lipid metabolism in tomato

Trichomes are basic and important barriers necessary for plants to resist environmental stress. Although several regulatory transcription factors have been found to play an important role in tomato (Solanum lycopersicum) multicellular trichome development, the regulatory network underlying trichome density in tomato is still limited. Our results demonstrated that a non-specific lipid transfer protein gene, SlnsLTP33, was identified as a downstream target gene of the trichome regulator SlHDZIV8 (an HD-Zip IV transcription factor). By knocking out or co-suppressing the SlnsLTP33 gene, tomato plants exhibit fewer trichomes, while overexpressing plants exhibit more trichomes. We found that SlnsLTP33 directly interacts with SlHDZIV8 or CUTIN DEFICIENT2 (CD2) and synergistically activates the transcriptional activity of SlCycB2 by binding to the promoter of SlCycB2. Collectively, our data uncover the essential role of the SlHDZIV8/CD2-SlnsLTP33 regulatory module in regulating multicellular trichome density in tomato. Further research has shown that SlnsLTP33 plays a crucial role in the accumulation of glycerophospholipids, glycerides, and fatty acyl, which may be closely related to trichome development. Our findings provide a novel gene and new insights into the regulatory network controlling trichome formation in tomato.