Advances in Understanding the Genetic Basis of Fatty Acids Biosynthesis in Perilla: An Update

Abstract

Perilla, also termed as purple mint, Chinese basil, or Perilla mint, is a flavoring herb widely used in East Asia. Both crude oil and essential oil are employed for consumption as well as industrial purposes. Fatty acids (FAs) biosynthesis and oil body assemblies in Perilla have been extensively investigated over the last three decades. Recent advances have been made in order to reveal the enzymes involved in the fatty acid biosynthesis in Perilla. Among those fatty acids, alpha-linolenic acid retained the attention of scientists mainly due to its medicinal and nutraceutical properties. Lipids synthesis in Perilla exhibited similarities with Arabidopsis thaliana lipids' pathway. The homologous coding genes for polyunsaturated fatty acid desaturases, transcription factors, and major acyl-related enzymes have been found in Perilla via de novo transcriptome profiling, genome-wide association study, and in silico whole-genome screening. The identified genes covered de novo fatty acid synthesis, acyl-CoA dependent Kennedy pathway, acyl-CoA independent pathway, Triacylglycerols (TAGs) assembly, and acyl editing of phosphatidylcholine. In addition to the enzymes, transcription factors including WRINKLED, FUSCA3, LEAFY COTYLEDON1, and ABSCISIC ACID INSENSITIVE3 have been suggested. Meanwhile, the epigenome aspect impacting the transcriptional regulation of FAs is still unclear and might require more attention from the scientific community. This review mainly outlines the identification of the key gene master players involved in Perilla FAs biosynthesis and TAGs assembly that have been identified in recent years. With the recent advances in genomics resources regarding this orphan crop, we provided an updated overview of the recent contributions into the comprehension of the genetic background of fatty acid biosynthesis. The provided resources can be useful for further usage in oil-bioengineering and the design of alpha-linolenic acid-boosted Perilla genotypes in the future.

Keywords: Perilla; fatty acid biosynthesis; fatty acid desaturase; genomics; oil crop; transcription factor; transcriptomics; triacylglycerol biosynthesis.

Figure 1

A simplified putative diagram view of fatty acids biosynthetic pathway in Perilla and triacylglycerols (TAGs) assembly. The schematic view involved bio-chemical interactions occurring in plastid, cytoplasm, and endoplasmic reticulum, respectively. The resulting TAGs are indicated in yellow. Purple circles indicate transcription factors, including WRINKLED (WRI1), FUSCA3 (FUS3), LEAFY COTYLEDON1 (LEC1, LCE2), and ABSCISIC ACID INSENSITIVE3 (ABI3). The transcriptional regulation of FUS3, LCE1, LCE2, and ABI3 with PfFAD3.1 is not yet uncovered. PDHC: plastidial pyruvate dehydrogenase complex; ACCase: acetyl-CoA carboxylase; MCMT: malonyl-CoA ACP transacylase; KASIII: ketoacyl-ACP synthase type III; KAR: 3-ketoacyl-ACP reductase; HAD: 3-hydroxyacyl-ACP dyhydratase; EAR: 2-enoyl-ACP reductase; KASII: ketoacyl-ACP synthase type II; KASI: ketoacyl-ACP synthase type I; SAD: stearoyl-acyl carrier protein desaturase; FATB: acyl-ACP thioesterase B; FATA: acyl-ACP thioesterase A; MGDG: monogalactosyldiacylglycerol; PfFAD: Perilla frutescens fatty acid desaturase; PC Pool: phosphatidylcholines pool; PCH: palmitoyl-CoA hydrolase; LACS: long-chain acyl-CoA synthetase; PDCT: phosphatidylcholinediacylglycerol cholinephosphotransferase; FAX: fatty acid export; LPCAT: lysophosphatidylcholine acyltransferase; PDAT: phospholipid diacylglycerol acyltransferase; DGAT: diacylglycerolacyltransferase; GPAT: glycerol-3-phosphate acyltransferase; LPAT: 1-acylglycerol-3-phosphate acyltransferase; DHAP: dihydroxyacetone phosphate; PAH: phosphatidic acid phosphatase; OLEO: Oleosin.