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SUMMARY: Very long‐chain fatty acids (VLCFAs) are important industrial raw materials and can be produced by genetically modified oil plants. For a long time, class A lysophosphatidic acid acyltransferase (LPAT) was considered unable to promote the accumulation of VLCFA in oil crops. The bottlenecks that the transgenic high VLCFA lines have an oil content penalty and the low amount of VLCFA in phosphatidylcholine remains intractable. In the present study, a class A LPAT2 from Camelina sativa (CsaLPAT2) promoting VLCFAs accumulation in phospholipid was found. Overexpression of CsaLPAT2 alone in Arabidopsis seeds significantly increased the VLCFA content in triacylglycerol, including C20:0, C20:2, C20:3, C22:0, and C22:1. The proportion of phosphatidic acid molecules containing VLCFAs in transgenic seeds reached up to 45%, which was 2.8‐fold greater than that in wild type. The proportion of phosphatidylcholine and diacylglycerol molecules containing VLCFAs also increased significantly. Seed size in CsaLPAT2 transgenic lines showed a slight increase without an oil content penalty. The total phospholipid content in the seed of the CsaLPAT2 transgenic line was significantly increased. Furthermore, the function of class A LPAT in promoting the accumulation of VLCFAs is conserved in the representative oil crops of Brassicaceae, such as C. sativa, Arabidopsis thaliana, Brassica napus, Brassica rapa, and Brassica oleracea. The findings of this study provide a promising gene resource for the production of VLCFAs. Significance Statement: A powerful and promising gene resource of LPAT2 belongs to class A from Camelina sativa, promoting the abundant accumulation of very long‐chain fatty acids in phosphatidic acid, which has not been previously recognized. [ABSTRACT FROM AUTHOR]

SUMMARY: Most flowering plants are hermaphrodites, but around 6% of species are dioecious, having separate male and female plants. Sex chromosomes and some sex‐specific genes have been reported in plants, but the genome sequences have not been compared. We now report the genome sequence of male and female jojoba (Simmondsia chinensis) plants, revealing a very large difference in the sex chromosomes. The male genome assembly was 832 Mb and the female 822 Mb. This was explained by the large size differences in the Y chromosome (37.6 Mb) compared with the X chromosome (26.9 Mb). Relative to the X chromosome, the Y chromosome had two large insertions each of more than 5 Mb containing more than 400 genes. Many of the genes in the chromosome‐specific regions were novel. These male‐specific regions included many flowering‐related and stress response genes. Smaller insertions found only in the X chromosome totalled 877 kb. The wide divergence of the sex chromosomes suggests a long period of adaptation to diverging sex‐specific roles. Male and female plants may have evolved to accommodate factors such as differing reproductive resource allocation requirements under the stress of the desert environment in which the plants are found. The sex‐determining regions accumulate genes beneficial to each sex. This has required the evolution of many more novel sex‐specific genes than has been reported for other organisms. This suggest that dioecious plants provide a novel source of genes for manipulation of reproductive performance and environmental adaptation in crops. Significance Statement: This is the first report comparing the whole genome sequences of male and female plants of any species. This manuscript reports the discovery of a large genome‐level divergence between male and female plants based upon the first whole genome sequencing analysis of male and female dioecious plants. [ABSTRACT FROM AUTHOR]

SUMMARY: Acetyl‐triacylglycerols (acetyl‐TAG) contain an acetate group in the sn‐3 position instead of the long‐chain fatty acid present in regular triacylglycerol (TAG). The acetate group confers unique physical properties such as reduced viscosity and a lower freezing point to acetyl‐TAG, providing advantages for use as emulsifiers, lubricants, and 'drop‐in' biofuels. Previously, the synthesis of acetyl‐TAG in the seeds of the oilseed crop camelina (Camelina sativa) was achieved through the heterologous expression of the diacylglycerol acetyltransferase gene EaDAcT, isolated from Euonymus alatus seeds that naturally accumulate high levels of acetyl‐TAG. Subsequent work identified a similar acetyltransferase, EfDAcT, in the seeds of Euonymus fortunei, that possesses higher in vitro activity compared to EaDAcT. In this study, the seed‐specific expression of EfDAcT in camelina led to a 20 mol% increase in acetyl‐TAG levels over that of EaDAcT. Coupling EfDAcT expression with suppression of the endogenous competing enzyme DGAT1 further enhanced acetyl‐TAG accumulation, up to 90 mol% in the best transgenic lines. Accumulation of high levels of acetyl‐TAG was stable over multiple generations, with minimal effect on seed size, weight, and fatty acid content. Slight delays in germination were noted in transgenic seeds compared to the wild type. EfDAcT transcript and protein levels were correlated during seed development with a limited window of EfDAcT protein accumulation. In high acetyl‐TAG producing lines, EfDAcT protein expression in developing seeds did not reflect the eventual acetyl‐TAG levels in mature seeds, suggesting that other factors limit acetyl‐TAG accumulation. Significance statement: Acetyl‐TAGs are unusually structured triacylglycerols with useful properties synthesized by diacylglycerol acetyltransferase (DAcT) enzymes. The expression of a DAcT variant with increased activity, combined with suppression of endogenous storage lipid synthesis, resulted in the very high accumulation of acetyl‐TAG in transgenic Camelina sativa seed. However, DAcT protein expression did not correlate with acetyl‐TAG accumulation in mature seeds, suggesting that other factors limit acetyl‐TAG synthesis at very high levels. [ABSTRACT FROM AUTHOR]

SUMMARY: Brassica napus is an important oilseed crop in the world, and the mechanism of seed oil biosynthesis in B. napus remains unclear. In order to study the mechanism of oil biosynthesis and generate germplasms for breeding, an ethyl methanesulfonate (EMS) mutant population with ~100 000 M2 lines was generated using Zhongshuang 11 as the parent line. The EMS‐induced genome‐wide mutations in M2−M4 plants were assessed. The average number of mutations including single nucleotide polymorphisms and insertion/deletion in M2−M4 was 21 177, 28 675 and 17 915, respectively. The effects of the mutations on gene function were predicted in M2−M4 mutants, respectively. We screened the seeds from 98 113 M2 lines, and 9415 seed oil content and fatty acid mutants were identified. We further confirmed 686 mutants with altered seed oil content and fatty acid in advanced generation (M4 seeds). Five representative M4 mutants with increased oleic acid were re‐sequenced, and the potential causal variations in FAD2 and ROD1 genes were identified. This study generated and screened a large scale of B. napus EMS mutant population, and the identified mutants could provide useful genetic resources for the study of oil biosynthesis and genetic improvement of seed oil content and fatty acid composition of B. napus in the future. Significance Statement: Seed oil content and fatty acid composition are important traits of oil crop Brassica napus. In this study, a large number of Brassica napus EMS mutants with altered seed oil content or fatty acid composition have been generated and identified. This study provides useful genetic resources for functional genomics study and genetic improvement of B. napus. [ABSTRACT FROM AUTHOR]

Summary: Gene‐editing techniques are currently revolutionizing biology, allowing far greater precision than previous mutagenic and transgenic approaches. They are becoming applicable to a wide range of plant species and biological processes. Gene editing can rapidly improve a range of crop traits, including disease resistance, abiotic stress tolerance, yield, nutritional quality and additional consumer traits. Unlike transgenic approaches, however, it is not facile to forensically detect gene‐editing events at the molecular level, as no foreign DNA exists in the elite line. These limitations in molecular detection approaches are likely to focus more attention on the products generated from the technology than on the process in itself. Rapid advances in sequencing and genome assembly increasingly facilitate genome sequencing as a means of characterizing new varieties generated by gene‐editing techniques. Nevertheless, subtle edits such as single base changes or small deletions may be difficult to distinguish from normal variation within a genotype. Given these emerging scenarios, downstream 'omics' technologies reflective of edited affects, such as metabolomics, need to be used in a more prominent manner to fully assess compositional changes in novel foodstuffs. To achieve this goal, metabolomics or 'non‐targeted metabolite analysis' needs to make significant advances to deliver greater representation across the metabolome. With the emergence of new edited crop varieties, we advocate: (i) concerted efforts in the advancement of 'omics' technologies, such as metabolomics, and (ii) an effort to redress the use of the technology in the regulatory assessment for metabolically engineered biotech crops. Significance Statement: Unlike with transgenic approaches, it is not facile to detect gene‐editing events forensically at the molecular level, as no foreign DNA exists in gene‐edited lines. The limitation in molecular detection approaches are likely to focus more attention on the products generated from the technology than on the process itself. Here, we highlight the use of metabolomics as a means to characterize (and in some cases identify) gene‐edited material and champion its use for regulatory purposes. [ABSTRACT FROM AUTHOR]

Summary: Despite well established roles of microRNAs in plant development, few aspects have been addressed to understand their effects in seeds especially on lipid metabolism. In this study, we showed that overexpressing microRNA167A (miR167OE) in camelina (Camelina sativa) under a seed‐specific promoter changed fatty acid composition and increased seed size. Specifically, the miR167OE seeds had a lower α‐linolenic acid with a concomitantly higher linoleic acid content than the wild‐type. This decreased level of fatty acid desaturation corresponded to a decreased transcriptional expression of the camelina fatty acid desaturase3 (CsFAD3) in developing seeds. MiR167 targeted the transcription factor auxin response factor (CsARF8) in camelina, as had been reported previously in Arabidopsis. Chromatin immunoprecipitation experiments combined with transcriptome analysis indicated that CsARF8 bound to promoters of camelina bZIP67 and ABI3 genes. These transcription factors directly or through the ABI3‐bZIP12 pathway regulate CsFAD3 expression and affect α‐linolenic acid accumulation. In addition, to decipher the miR167A‐CsARF8 mediated transcriptional cascade for CsFAD3 suppression, transcriptome analysis was conducted to implicate mechanisms that regulate seed size in camelina. Expression levels of many genes were altered in miR167OE, including orthologs that have previously been identified to affect seed size in other plants. Most notably, genes for seed coat development such as suberin and lignin biosynthesis were down‐regulated. This study provides valuable insights into the regulatory mechanism of fatty acid metabolism and seed size determination, and suggests possible approaches to improve these important traits in camelina. Significance Statement: The fatty acid composition of oil and seed size are among the most important traits of oilseeds. Overexpression of a microRNA, the key post‐transcriptional regulator, caused decreased α‐linolenic acid content and increased seed size in the oilseed crop Camelina sativa, and provided a powerful tool for deciphering regulatory mechanisms that affect fatty acid biosynthesis and seed development. [ABSTRACT FROM AUTHOR]

Summary: Despite the importance of oilseeds to worldwide human nutrition, and more recently to the production of bio‐based diesel fuels, the detailed mechanisms regulating seed oil biosynthesis remain only partly understood, especially from a tissue‐specific perspective. Here, we investigated the spatial distributions of lipid metabolites and transcripts involved in oil biosynthesis from seeds of two low‐erucic acid genotypes of Brassica napus with high and low seed‐oil content. Integrated results from matrix‐assisted laser desorption/ionization‐mass spectrometry imaging (MALDI‐MSI) of lipids in situ, lipidome profiling of extracts from seed tissues, and tissue‐specific transcriptome analysis revealed complex spatial distribution patterns of lipids and transcripts. In general, it appeared that many triacylglycerol and phosphatidylcholine species distributed heterogeneously throughout the embryos. Tissue‐specific transcriptome analysis identified key genes involved in de novo fatty acid biosynthesis in plastid, triacylglycerols assembly and lipid droplet packaging in the endoplasmic reticulum (ER) that may contribute to the high or low oil phenotype and heterogeneity of lipid distribution. Our results imply that transcriptional regulation represents an important means of impacting lipid compartmentalization in oil seeds. While much information remains to be learned about the intricacies of seed oil accumulation and distribution, these studies highlight the advances that come from evaluating lipid metabolism within a spatial context and with multiple omics level datasets. [ABSTRACT FROM AUTHOR]

Metabolism in plants is compartmentalized among different tissues, cells and subcellular organelles. Mass spectrometry imaging ( MSI) with matrix-assisted laser desorption ionization ( MALDI) has recently advanced to allow for the visualization of metabolites at single-cell resolution. Here we applied 5- and 10 μm high spatial resolution MALDI- MSI to the asymmetric Kranz anatomy of Zea mays (maize) leaves to study the differential localization of two major anionic lipids in thylakoid membranes, sulfoquinovosyldiacylglycerols ( SQDG) and phosphatidylglycerols ( PG). The quantification and localization of SQDG and PG molecular species, among mesophyll (M) and bundle sheath ( BS) cells, are compared across the leaf developmental gradient from four maize genotypes (the inbreds B73 and Mo17, and the reciprocal hybrids B73 × Mo17 and Mo17 × B73). SQDG species are uniformly distributed in both photosynthetic cell types, regardless of leaf development or genotype; however, PG shows photosynthetic cell-specific differential localization depending on the genotype and the fatty acyl chain constituent. Overall, 16:1-containing PGs primarily contribute to the thylakoid membranes of M cells, whereas BS chloroplasts are mostly composed of 16:0-containing PGs. Furthermore, PG 32:0 shows genotype-specific differences in cellular distribution, with preferential localization in BS cells for B73, but more uniform distribution between BS and M cells in Mo17. Maternal inheritance is exhibited within the hybrids, such that the localization of PG 32:0 in B73 × Mo17 is similar to the distribution in the B73 parental inbred, whereas that of Mo17 × B73 resembles the Mo17 parent. This study demonstrates the power of MALDI- MSI to reveal unprecedented insights on metabolic outcomes in multicellular organisms at single-cell resolution. [ABSTRACT FROM AUTHOR]

The cutin polymers of different fruit cuticles (tomato, apple, nectarine) were examined using matrix-assisted laser desorption/ionization mass spectrometry imaging ( MALDI MSI) after in situ release of the lipid monomers by alkaline hydrolysis. The mass spectra were acquired from each coordinate with a lateral spatial resolution of approximately 100 μm. Specific monomers were released at their original location in the tissue, suggesting that post-hydrolysis diffusion can be neglected. Relative quantification of the species was achieved by introducing an internal standard, and the collection of data was subjected to non-supervised and supervised statistical treatments. The molecular images obtained showed a specific distribution of ions that could unambiguously be ascribed to cutinized and suberized regions observed at the surface of fruit cuticles, thus demonstrating that the method is able to probe some structural changes that affect hydrophobic cuticle polymers. Subsequent chemical assignment of the differentiating ions was performed, and all of these ions could be matched to cutin and suberin molecular markers. Therefore, this MALDI- MSI procedure provides a powerful tool for probing the surface heterogeneity of plant lipid polymers. This method should facilitate rapid investigation of the relationships between cuticle phenotypes and the structure of cutin within a large population of mutants. [ABSTRACT FROM AUTHOR]