We report n-6 monounsaturated primary alcohols (C 26:1 , C 28:1 , and C 30:1 homologs) in the cuticular waxes of Arabidopsis (Arabidopsis thaliana) inflorescence stem, a class of wax not previously reported in Arabidopsis. The Arabidopsis cer17 mutant was completely deficient in these monounsaturated alcohols, and CER17 was found to encode a predicted ACYL-COENZYME A DESATURASE LIKE4 (ADS4). Studies of the Arabidopsis cer4 mutant and yeast variously expressing CER4 (a predicted fatty acyl-CoA reductase) with CER17/ADS4, demonstrated CER4's principal role in synthesis of these monounsaturated alcohols. Besides unsaturated alcohol deficiency, cer17 mutants exhibited a thickened and irregular cuticle ultrastructure and increased amounts of cutin monomers. Although unsaturated alcohols were absent throughout the cer17 stem, the mutation's effects on cutin monomers and cuticle ultrastructure were much more severe in distal than basal stems, consistent with observations that the CER17/ADS4 transcript was much more abundant in distal than basal stems. Furthermore, distal but not basal stems of a double mutant deficient for both CER17/ADS4 and LONG-CHAIN ACYL-COA SYNTHETASE1 produced even more cutin monomers and a thicker and more disorganized cuticle ultrastructure and higher cuticle permeability than observed for wild type or either mutant parent, indicating a dramatic genetic interaction on conversion of very long chain acyl-CoA precursors. These results provide evidence that CER17/ADS4 performs n-6 desaturation of very long chain acyl-CoAs in both distal and basal stems and has a major function associated with governing cutin monomer amounts primarily in the distal segments of the inflorescence stem. Plant cuticle coats most aerial surfaces of vascular plants and plays a major role in coordinating interactions between the plant and its environment (Rensing et al., 2008; Yeats and Rose, 2013). The cuticle is primarily composed of two lipid classes, the non-polymerized (free) cuticular waxes and the cutin polyester, both of which are synthesized by epidermal cells. Common plant wax compounds are the very long chain fatty acids (VLCFAs) and their derivatives including aldehydes, primary alcohols, alkanes, secondary alcohols, ketones, and esters (Samuels et al., 2008). As much as 4.0% of total waxes on Arabidopsis (Ara-bidopsis thaliana) inflorescence stems are composed of numerous yet unidentified wax compounds (Jenks et al., 1995). Cutin consists primarily of C 16 and C 18 fatty acid derivatives (e.g. hydroxy fatty acids and dicar-boxylic acids), which are linked by ester bonds; however , glycerol and small amounts of longer chain cutin monomers have also been reported (Pollard et al., 2008). In the past decade, there has been significant progress toward understanding the molecular mechanisms controlling the cuticular wax biosynthetic pathway based primarily on studies of wax-deficient mutants (Bernard and Joubès, 2013; Yeats and Rose, 2013). Synthesis of wax occurs in epidermal cells and begins with C 16 and C 18 lon...

Soybean (Glycine max) is one of the most important oilseed crops. However, the regulatory mechanism that governs the process of oil accumulation in soybean remains poorly understood.In this study, GmZF392, a tandem CCCH zinc finger (TZF) protein which was identified in our previous RNA-seq analysis of seed-preferred transcription factors, was found to function as a positive regulator of lipid production.GmZF392 promotes seed oil accumulation in both transgenic Arabidopsis and stable transgenic soybean plants by binding to a bipartite cis-element, containing TG-and TA-rich sequences, in promoter regions, activating the expression of genes in the lipid biosynthesis pathway. GmZF392 physically interacts with GmZF351, our previously identified transcriptional regulator of lipid biosynthesis, to synergistically promote downstream gene expression. Both GmZF392 and GmZF351 are further upregulated by GmNFYA, another transcription factor involved in lipid biosynthesis, directly (in the former case) and indirectly (in the latter case). Promoter sequence diversity analysis showed that the GmZF392 promoter may have been selected at the origin of the Glycine genus and further mildly selected during domestication from wild soybeans to cultivated soybeans.Our study reveals a regulatory module containing three transcription factors in the lipid biosynthesis pathway, and manipulation of the module may improve oil production in soybean and other oilseed crops.