HtDCR-like1 regulates the development of structurally coloured cuticle by modulating cuticle chemistry and mechanical properties in Hibiscus trionum

Structural colours are a unique trait present in some animals, plants and even bacteria. In Hibiscus trionum flowers, they arise from nano-scaled cuticular ridges and may improve pollinator foraging efficiency. These ridges result from the buckling of the cuticle which is thought to be controlled by multiple parameters including anisotropic cell growth, chemical differentiation of the cuticle and formation of two layers of different mechanical properties.

Here we investigate further the molecular and physical mechanisms by which structural colours are achieved in Hibiscus trionum . We produced two transgenic lines overexpressing HtDCR-like1 , encoding a BAHD acyltransferase involved in cuticle synthesis. Transgenic lines showed impairment of the production of cuticle striations. Cuticle thickness, cuticle chemistry, cell elongation and cuticle stiffness were then investigated to identify the cause of failed buckling.

We found that HtDCR-like1 overexpression leads to modification of cuticle chemistry, including a decrease in detectable C ₁₆ H ₃₂ O ₄ (10,16-DHP) and a change to the measured Young’s moduli of the cuticle layers without alteration of the cell growth pattern.

This work demonstrates the mechanisms by which gene regulation may control complex physical phenomena such as cuticle buckling via alteration of material properties of living tissues.