Maize Glossy2 and Glossy2-like Genes Have Overlapping and Distinct Functions in Cuticular Lipid Deposition

Abstract

<p>Plant epidermal cells express unique molecular machinery that juxtapose the assembly of intracellular lipid components and the unique extracellular cuticular lipids that are unidirectionally secreted to plant surfaces. In maize (<em>Zea mays</em>), mutations at the <em>glossy2 (gl2)</em> locus affect the deposition of extracellular cuticular lipids. Sequence-based genome scanning identified a new <em>Gl2</em> homolog in the maize genome, namely <em>Gl2-like</em>. Both the <em>Gl2-like</em> and <em>Gl2</em> genes are members of the BAHD superfamily of acyltransferases, with close sequence similarity to the Arabidopsis (<em>Arabidopsis thaliana</em>) <em>CER2</em> gene. Transgenic experiments demonstrated that <em>Gl2-like</em> and <em>Gl2</em> functionally complement the Arabidopsis <em>cer2</em> mutation, with differential influences on the cuticular lipids and the lipidome of the plant, particularly affecting the longer alkyl chain acyl lipids, especially at the 32-carbon chain length. Site-directed mutagenesis of the putative BAHD catalytic HXXXDX-motif indicated that <em>Gl2-like</em> requires this catalytic capability to fully complement the <em>cer2</em> function, but <em>Gl2</em> can accomplish complementation without the need for this catalytic motif. These findings demonstrate that <em>Gl2</em> and <em>Gl2-like</em> overlap in their cuticular lipid function, but have evolutionarily diverged to acquire nonoverlapping functions.</p>