The First Intron of DIACYLGLYCEROL ACYLTRANSFERASE 1 Regulates Pollen and Embryo Lipid Accumulation in Arabidopsis

Authors: MCGUIRE, SEAN - Washington State University; Shockey, Jay; BATES, PHILIP - Washington State University

Submitted to: New Phytologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/22/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: The rapidly growing world population has created great urgency to increase food and feed productivity from agricultural lands. The seed oils from oilseed crops, such as soybean, cotton, and canola, provide a large portion of the caloric intake for fats in human and animal diets. Increased yields of plant oils per unit of cultivated land has increased over recent decades, but only slowly. To improve yields further, a better understanding of the underlying genetic controls in oilseeds must be obtained. In this study, the role of a little-known genetic module called intron 1, found in a family of key oil synthesizing genes, was characterized. Compared to lines engineered without it, intron 1-expressing lines provided better functionality, resulting in full replacement of the host plant gene, which had not been reported previously. Future engineering strategies in other agronomic oilseed varieties may also include intron 1.

Technical Abstract: Tissue-specific accumulation of triacylglycerols (TAGs) is crucial during various stages of plant development. Two enzymes share overlapping functions to produce TAGs, namely acyl-CoA:diacylglycerol acyltransferase 1 (DGAT1) and phospholipid:diacylglycerol acyltransferase 1 (PDAT1). The absence of both genes in a dgat1-1/pdat1-2 double mutant is pollen and embryo lethal. The key regulatory elements controlling tissue-specific expression of both genes have not yet been identified. To rescue the lethality, a dgat1-1/dgat1-1//PDAT1/pdat1-2 parent was transformed with transgenic constructs containing the Arabidopsis DGAT1 promoter fused to the AtDGAT1 open reading frame (ORF) either with or without the first intron. Triple homozygous mutant plants were successfully obtained, however, in the absence of the first intron anthers fail to fill with pollen, total seed yield is ~10% of wild-type, seed oil content remains reduced (similar to the dgat1-1 mutant), and non-Mendelian segregation of the PDAT1/pdat1-2 locus occurs. In contrast, mutant plants expressing the AtDGAT1pro:AtDGAT1 transgene with the first intron mostly recover all phenotypes to or near wild-type. Phylogenetic alignment of plant DGAT1s and motif analysis indicates that the first intron of DGAT1s from various plant species share common transcription factor binding sites, suggesting first intron functionality may be shared amongst diverged plant lineages. These results establish that the combination of the promoter and first intron of AtDGAT1 provides the proper context for temporal and tissue-specific expression of DGAT1 activity in pollen and embryos. Furthermore, we demonstrate that these regulatory elements can be used as genetic tools to functionally replace TAG biosynthetic enzymes in Arabidopsis.