EgMIXTA1, a MYB-Type Transcription Factor, Promotes Cuticular Wax Formation in Eustoma grandiflorum Leaves

Abstract

In the aerial plant organs, cuticular wax forms a hydrophobic layer that can protect cells from dehydration, repel pathogen attacks, and prevent organ fusion during development. The <i>MIXTA</i> gene encodes an MYB-like transcription factor, which is associated with epicuticular wax biosynthesis to increase the wax load on the surface of leaves. In this study, the <i>AmMIXTA</i>-homologous gene <i>EgMIXTA1</i> was functionally characterized in the <i>Eustoma grandiflorum</i>. <i>EgMIXTA1</i> was ubiquitously, but highly, expressed in leaves and buds. We identified the <i>Eustoma</i> MIXTA homolog and developed the plants for overexpression. EgMIXTA1-overexpressing plants had more wax crystal deposition on the leaf surface compared to wild-type and considerably more overall cuticular wax. In the leaves of the overexpression line, the cuticular transpiration occurred more slowly than in those of non-transgenic plants. Analysis of gene expression indicated that several genes, such as <i>EgCER3</i>, <i>EgCER6</i>, <i>EgCER10</i>, <i>EgKCS1</i>, <i>EgKCR1</i>, and <i>EgCYP77A6</i>, which are known to be involved in wax biosynthesis, were induced by EgMIXTA1-overexpression lines. Expression of another gene, <i>WAX INDUCER1/SHINE1</i>, encoding a transcription factor that stimulates the production of cutin, was also significantly higher in the overexpressors than in wild-type. However, the expression of a lipid-related gene, <i>EgABCG12</i>, did not change relative to the wild-type. These results suggest that <i>EgMIXTA1</i> is involved in the biosynthesis of cuticular waxes.