Abstract
Cuticular wax is a major component of the surface cuticle of plants, which performs crucial functions in optimizing plant growth. Histone acetylation regulates gene expression in diverse biological processes, but its role in cuticular wax synthesis is not well understood. In this study, we observed that mutations of the Arabidopsis thaliana histone acetyltransferase GENERAL CONTROL NON-REPRESSED PROTEIN5 (GCN5) impaired the accumulation of stem cuticular wax. Three target genes of GCN5, ECERIFERUM3 (CER3), CER26, and CER1-LIKE1 (CER1-L1), were identified by RNA-seq and ChIP assays. H3K9/14 acetylation levels at the promoter regions of CER3, CER26, and CER1-L1 were consistently and significantly decreased in the gcn5-2 mutant as compared to the wild-type. Notably, overexpression of CER3 in the gcn5-2 mutant rescued the defect in stem cuticular wax biosynthesis. Collectively, these data demonstrate that GCN5 is involved in stem cuticular wax accumulation by modulating CER3 expression via H3K9/14 acetylation, which underlines the important role of histone acetylation in cuticular wax biosynthesis.
Highlights
Plant cuticular wax is a complex mixture of very-long-chain fatty acids (VLCFAs) and aldehydes, alcohols, alkanes, ketones, and esters, with predominant carbon chain-lengths ranging from C22 to C36 (Samuels et al, 2008; Li et al, 2016), and it forms one of the major lipid components of the cuticle that covers the outer surface of aerial plant tissues.The biosynthesis of cuticular wax is processed through two distinct pathways, termed the alcohol-forming and the alkane-forming pathways, which yield 17~18% and 80% of the total amount of wax, respectively (Bernard and Joubès, 2013)
Fewer stem wax crystals were observed on the surface of the gcn5-2 mutant relative to the wild-type (Ws), which led to the appearance of a glossy stem (Fig. 1A, B)
Mutation of GENERAL CONTROL NON-REPRESSED PROTEIN5 (GCN5) in Arabidopsis compromised the content of multiple lipid compounds, which resulted in a complete deficiency in stem cuticular wax accumulation.This wax deficiency could be fully rescued by complementation with 35S::GCN5
Summary
Plant cuticular wax is a complex mixture of very-long-chain fatty acids (VLCFAs) and aldehydes, alcohols, alkanes, ketones, and esters, with predominant carbon chain-lengths ranging from C22 to C36 (Samuels et al, 2008; Li et al, 2016), and it forms one of the major lipid components of the cuticle that covers the outer surface of aerial plant tissues.The biosynthesis of cuticular wax is processed through two distinct pathways, termed the alcohol-forming and the alkane-forming pathways, which yield 17~18% and 80% of the total amount of wax, respectively (Bernard and Joubès, 2013). As for the essential alkane-forming pathway, CER3/WAX2 plays an important role in synthesis of major wax components (Aarts et al, 1995; Chen et al, 2003; Rowland et al, 2007; Lee and Suh, 2015).The amount of wax found in the cer mutant was severely reduced compared with the wild-type in Arabidopsis stems, especially with regards to aldehydes, alkanes, secondary alcohols, and ketones (Rowland et al, 2007). The exact reactions catalysed by the CER3 enzyme remain unknown, it has been reported that CER3 may physically interact with CER1 and CYTOCHROME B5 ISOFORM (CYTB5) for the biosynthesis of very-long-chain alkanes (Bernard et al, 2012)
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