Evaluation of the functional role of the maize Glossy2 and Glossy2-like genes in cuticular lipid deposition

ABSTRACT

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 (Zea mays L.), mutations at the glossy2 (gl2) locus affect the deposition of extracellular cuticular lipids. Sequence-based genome scanning identified a novel gl2 homolog in the maize genome, Gl2-like. Sequence homology identifies that both the Gl2-like and Gl2 genes are members of the BAHD superfamily of acyltransferases, with close sequence homology to the Arabidopsis CER2 gene. Transgenic experiments demonstrate that Gl2-like and Gl2 functionally complement the Arabidopsis cer2 mutation, with differential impacts on the cuticular lipids and the lipidome of the plant, particularly affecting the longer alkyl chain acyl lipids, particularly at the 32-carbon chain length. Site-directed mutagenesis of the putative BAHD catalytic HXXXDX-motif indicates that Gl2-like requires this catalytic capability to fully complement the cer2 function, but Gl2 can accomplish this without the need for this catalytic motif. These findings demonstrate that both Gl2 and Gl2-like overlap in their cuticular lipid function, however the two genes have evolutionary diverged to acquire non-overlapping functions.