Three endoplasmic reticulum-associated fatty acyl-coenzyme a reductases were involved in the production of primary alcohols in hexaploid wheat (Triticum aestivum L.)

Abstract

BackgroundThe cuticle covers the surface of the polysaccharide cell wall of leaf epidermal cells and forms an essential diffusion barrier between the plant and the environment. The cuticle is composed of cutin and wax. Cuticular wax plays an important role in the survival of plants by serving as the interface between plants and their biotic and abiotic environments, especially restricting nonstomatal water loss. Leaf cuticular waxes of hexaploid wheat at the seedling stage mainly consist of primary alcohols, aldehydes, fatty acids, alkane and esters. Primary alcohols account for more than 80% of the total wax load. Therefore, we cloned several genes encoding fatty acyl-coenzyme A reductases from wheat and analyzed their function in yeast and plants. We propose the potential use of these genes in wheat genetic breeding.ResultsWe reported the cloning and characterization of three TaFARs, namely TaFAR6, TaFAR7 and TaFAR8, encoding fatty acyl-coenzyme A reductases (FAR) in wheat leaf cuticle. Expression analysis revealed that TaFAR6, TaFAR7 and TaFAR8 were expressed at the higher levels in the seedling leaf blades, and were expressed moderately or weakly in stamen, glumes, peduncle, flag leaf blade, sheath, spike, and pistil. The heterologous expression of three TaFARs in yeast (Saccharomyces cerevisiae) led to the production of C24:0 and C26:0 primary alcohols. Transgenic expression of the three TaFARs in tomato (Solanum lycopersicum) and rice (Oryza sativa) led to increased accumulation of C24:0–C30:0 primary alcohols. Transient expression of GFP protein-tagged TaFARs revealed that the three TaFAR proteins were localized to the endoplasmic reticulum (ER), the site of wax biosynthesis. The three TaFAR genes were transcriptionally induced by drought, cold, heat, powdery mildew (Blumeria graminis) infection, abscisic acid (ABA) and methyl jasmonate (MeJa) treatments.ConclusionsThese results indicated that wheat TaFAR6, TaFAR7 and TaFAR8 are involved in biosynthesis of very-long-chain primary alcohols in hexaploid wheat and in response to multiple environmental stresses.Electronic supplementary materialThe online version of this article (10.1186/s12870-018-1256-y) contains supplementary material, which is available to authorized users.

TaCER1‐1A is involved in cuticular wax alkane biosynthesis in hexaploid wheat and responds to plant abiotic stresses

“…In the present study, we further found that various adverse conditions or stresses, including low temperature and drought, induced TaCER1‐1A expression within hours and led to increased accumulation of alkanes in wheat wax. This finding is similar to previous reports on other plant species, where diverse wax biosynthesis genes were found induced by stress conditions as well as plant hormones involved in stress responses: Drought, osmotic stress, or ABA treatment strongly induced expression, for example, of the Arabidopsis CER6 and CER1 genes (Bourdenx et al, ; Hooker, Millar, & Kunst, ; Kosma et al, ) and of diverse wax biosynthesis genes in bread wheat and Brachypodium (Chai et al, ; Wang, et al, 2015b; Wang, et al, 2015c; Wang et al, ).…”

“…Similar effects were also observed for rice and cucumber CER1 homologs (Wang, Zhang, Xu, Ren, et al, 2015;Zhou et al, 2013). Overall, our results confirmed that genes (Bourdenx et al, 2011;Hooker, Millar, & Kunst, 2002;Kosma et al, 2009) and of diverse wax biosynthesis genes in bread wheat and Brachypodium (Chai et al, 2018;Wang, et al, 2015b;Wang, et al, 2015c;Wang et al, 2016).…”

“…Recent reports revealed that β‐diketone formation largely depends on genes clustered in the W1, W2, and W3 loci residing on different chromosomes in separate subgenomes (Adamski et al, ; Tsunewaki & Ebana, ; Zhang et al, ). Other studies showed that at least eight functional FAR enzymes are involved in formation of VLC primary alcohols, all with different expression profiles (Chai et al, ; Wang, et al, 2015b; Wang, et al, 2015c; Wang et al, ). The present work further underscores the high redundancy among wax biosynthesis genes in wheat, demonstrating that its genome contains nine CER1 homologs with characteristic expression patterns.…”

“…TAA1a was the first gene verified to function in the synthesis of fatty alcohols, encoding a FAR specifically expressed in wheat anthers (Wang et al, ). More recently, eight other FARs encoded by TaFAR genes were found involved in biosynthesis of wax alcohols in various wheat organs (Chai et al, ; Wang et al, ; Wang, Wang, Sun, Hegebarth, et al, ; Wang, Wang, Sun, Wang, et al, ). Simultaneously, also several genes crucial for β‐diketone biosynthesis in wheat (and barley) have been identified (Hen‐Avivi et al, ; Schneider et al, ), including a hydrolase that likely generates crucial ketoacyl precursors for β‐diketone formation (Hen‐Avivi et al, ).…”

“…TaFAR genes were found involved in biosynthesis of wax alcohols in various wheat organs (Chai et al, 2018;Wang et al, 2016;Wang, Wang, Sun, Hegebarth, et al, 2015;. Simultaneously, also several genes crucial for β-diketone biosynthesis in wheat (and barley) have been identified Schneider et al, 2016), including a hydrolase that likely generates crucial ketoacyl precursors for β-diketone formation .…”