The NAC transcription factor LpNAC48 promotes trichome formation in Lilium pumilum

Trichomes play a crucial role in plant resistance to abiotic and biotic stresses, and their development and characteristics vary across different species. This study demonstrates that trichomes of Lilium pumilum exhibit synchronized growth during flower bud differentiation and enhance the plant's adaptability to UV-B radiation and aphid infection. We identified LpNAC48, a NAC family transcription factor (TF), that interacted with the B-box (BBX) family TF LpBBX28 during trichome formation in L. pumilum. Silencing LpNAC48 or LpBBX28 impaired trichome development and reduced trichome density on the outer perianths. We demonstrated that the upstream regulators LpNAC48 and LpBBX28 directly bound to the promoter of the bHLH TF-encoding gene LpGL3-LIKE (LpGL3L) to activate its expression. Moreover, an ABA-responsive element within a 259-bp DNA variation in the LpNAC48 promoter was important for its expression and was bound by the bZIP TF LpbZIP29 during trichome development. This binding activated LpNAC48 expression and contributed to trichome formation. This study provides insights into the role of a small DNA sequence variation in gene expression and trichome traits. Three key transcription factors compose a regulatory module that promotes trichome formation in lily.