Natural variation of GmFATA1B regulates seed oil content and composition in soybean

Transcriptome analyses of Acer Truncatum Bunge seeds to delineate the genes involved in fatty acid metabolism

BACKGROUND

Acer truncatum Bunge is an economic, ecological, oil, and medicinal tree, and its kernel oil is rich in nervonic acid. It is crucial to explore the transcriptional expression patterns of genes affecting fatty acid synthesis to improve the quality of Acer truncatum oil.

RESULTS

This study used the seeds from high fatty acid strain YQC and those from low fatty acid strain Y38 as the test materials. Specifically, we performed a comparative transcriptome analysis of Y38 seeds and YQC to identify differentially expressed genes (DEGs) at two time points (seeds 30 days after the blooming period and 90 days after the blooming period). Compared with YQC_1 (YQC seeds at 30 days after the blooming period), a total of 3,618 DEGs were identified, including 2,333 up-regulated and 1,285 downregulated DEGs in Y38_1 (Y38 seeds at 30 days after blooming period). In the Y38_2 (Y38 seeds at 90 days after the blooming period) versus YQC_2 (YQC seeds at 90 days after the blooming period) comparison group, 9,340 genes were differentially expressed, including 5,422 up-regulated and 3,918 down-regulated genes. The number of DEGs in Y38 compared to YQC was significantly higher in the late stages of seed development. Gene functional enrichment analyses showed that the DEGs were mainly involved in the fatty acid biosynthesis pathway. And two fatty acid synthesis-related genes and seven nervonic acid synthesis-related genes were validated by qRT-PCR.

CONCLUSIONS

This study provides a basis for further research on biosynthesizing fatty acids and nervonic acidnervonic acids in A. truncatum seeds.

The acyl-acyl carrier protein thioesterases GmFATA1 and GmFATA2 are essential for fatty acid accumulation and growth in soybean

Acyl-acyl carrier protein (ACP) thioesterases (FAT) hydrolyze acyl-ACP complexes to release FA in plastids, which ultimately affects FA biosynthesis and profiles. Soybean GmFATA1 and GmFATA2 are homoeologous genes encoding oleoyl-ACP thioesterases whose role in seed oil accumulation and plant growth has not been defined. Using CRISPR/Cas9 gene editing mutation of Gmfata1 or 2 led to reduced leaf FA content and growth defect at the early seedling stage. In contrast, no homozygous double mutants were obtained. Combined this indicates that GmFATA1 and GmFATA2 display overlapping, but not complete functional redundancy. Combined transcriptomic and lipidomic analysis revealed a large number of genes involved in FA synthesis and FA chain elongation are expressed at reduced level in the Gmfata1 mutant, accompanied by a lower triacylglycerol abundance at the early seedling stage. Further analysis showed that the Gmfata1 or 2 mutants had increased composition of the beneficial FA, oleic acid. The growth defect of Gmfata1 could be at least partially attributed to reduced acetyl-CoA carboxylase activity, reduced abundance of five unsaturated monogalactosyldiacylglycerol lipids, and altered chloroplast morphology. On the other hand, overexpression of GmFATA in soybean led to significant increases in leaf FA content by 5.7%, vegetative growth, and seed yield by 26.9%, and seed FA content by 23.2%. Thus, overexpression of GmFATA is an effective strategy to enhance soybean oil content and yield.