Three Fatty Acyl-Coenzyme A Reductases, BdFAR1, BdFAR2 and BdFAR3, are Involved in Cuticular Wax Primary Alcohol Biosynthesis in Brachypodium distachyon

Abstract

Plant cuticular wax is a heterogeneous mixture of very long chain fatty acids (VLCFAs) and their derivatives. Primary alcohols are the dominant wax components throughout leaf development of Brachypodium distachyon (Brachypodium). However, the genes involved in primary alcohol biosynthesis have not been investigated and their exact biological function remains unclear in Brachypodium to date. Here, we monitored the leaf wax profile and crystal morphology during Brachypodium leaf morphogenesis, and isolated three Brachypodium fatty acyl-CoA reductase (FAR) genes, named BdFAR1, BdFAR2 and BdFAR3, then analyzed their biochemical activities, substrate specificities, expression patterns, subcellular localization and stress induction. Transgenic expression of BdFAR genes in yeast (Saccharomyces cerevisiae), tomato (Solanum lycopersicum), Arabidopsis (Arabidopsis thaliana) and Brachypodium increased the production of primary alcohols. The three BdFAR genes were preferentially expressed in Brachypodium aerial tissues, consistent with known sites of wax primary alcohol deposition, and localized in the endoplasmic reticulum (ER) in Arabidopsis protoplasts. Finally, expression of the BdFAR genes was induced by drought, cold and ABA treatments, and drought stress significantly increased cuticular wax accumulation in Brachypodium. Taken together, these results indicate that the three BdFAR genes encode active FARs involved in the biosynthesis of Brachypodium wax primary alcohols and respond to abiotic stresses.

Expression Analysis and Functional Characterization of CER1 Family Genes Involved in Very-Long-Chain Alkanes Biosynthesis in Brachypodium distachyon

“…In our study, to assess the influence of drought stress on leaf cuticular wax accumulation in B. distachyon , both water deficit and PEG treatments were performed. Results showed that the cuticular wax of control plants mainly contained primary alcohols, alkanes, aldehydes, and fatty acids, in which primary alcohols were dominant components with few contents of other compounds ( Figure 1 ), which is consistent with the results of a recent study that the leaf cuticular wax of B. distachyon mainly consists of primary alcohols with less contents of aldehydes, alkanes, and fatty acids throughout leaf development (Wang et al, 2018). All treatments resulted in significant increases of total wax load and individual compound without changing wax composition ( Figure 1 ).…”

“…On the other hand, three BdFAR genes ( BdFAR1 , BdFAR2 , and BdFAR3 ) have been demonstrated to be involved in the alcohol-forming pathway and they respond to abiotic stresses in B. distachyon (Wang et al, 2018). These results together suggest that the cuticular wax biosynthetic pathways in B. distachyon are similar to those in Arabidopsis, containing both the alcohol-forming and the alkane-forming pathways.…”

“…These results together suggest that the cuticular wax biosynthetic pathways in B. distachyon are similar to those in Arabidopsis, containing both the alcohol-forming and the alkane-forming pathways. The leaf cuticular wax of B. distachyon consists of primary alcohols, aldehydes, alkanes, and fatty acids, among which primary alcohols are the dominant wax components throughout leaf development, accounting for 82–89% of total wax contents (Wang et al, 2018). Our work also shows that primary alcohols are the dominant wax components, which accounts for 89.6% of total wax load in control plants ( Figure 1A , Supplementary Table 1 ).…”

“…It is also generally known that wax-related genes are involved in regulatory networks of cuticular wax biosynthesis under diverse environments (Lee and Suh, 2013). Many genes, such as CER1 in Arabidopsis (Kosma et al, 2009), OsGL1s in rice (Jung et al, 2006; Islam et al, 2009; Qin et al, 2011; Zhou et al, 2013; Zhou et al, 2015), CsCER1 and CsWAX2 in cucumber (Wang et al, 2015a, Wang et al, 2015b), and BdFARs in B. distachyon (Wang et al, 2018), respond to drought, sodium chloride, cold, and ABA treatments. In our study, qRT-PCR was performed to elucidate the expression patterns of BdCER1 genes under ABA, drought, PEG, and sodium chloride treatments.…”

Changes in Beneficial C-glycosylflavones and Policosanol Content in Wheat and Barley Sprouts Subjected to Differential LED Light Conditions

“…Studies have also shown that the number of FAR genes and their functions may vary, according to species-specific genetics. In other crops, it is evident that FAR2 and FAR3 are responsible for the biosynthesis of C 26 and C 28 primary alcohols [41]. Another report has claimed that at least five FARs are responsible for primary alcohol (C 16 to C 28 ) biosynthesis in Aegilops tauschii [42].…”