Abstract
PHOSPHOLIPID:DIACYLGLYCEROL ACYLTRANSFERASE (PDAT) is an enzyme that catalyzes the transfer of a fatty acyl moiety from the sn-2 position of a phospholipid to the sn-3-position of sn-1,2-diacylglyerol, thus forming triacylglycerol and a lysophospholipid. Although the importance of PDAT in triacylglycerol biosynthesis has been illustrated in some previous studies, the evolutionary relationship of plant PDATs has not been studied in detail. In this study, we investigated the evolutionary relationship of the PDAT gene family across the green plants using a comparative phylogenetic framework. We found that the PDAT candidate genes are present in all examined green plants, including algae, lowland plants (a moss and a lycophyte), monocots, and eudicots. Phylogenetic analysis revealed the evolutionary division of the PDAT gene family into seven major clades. The separation is supported by the conservation and variation in the gene structure, protein properties, motif patterns, and/or selection constraints. We further demonstrated that there is a eudicot-wide PDAT gene expansion, which appears to have been mainly caused by the eudicot-shared ancient gene duplication and subsequent species-specific segmental duplications. In addition, selection pressure analyses showed that different selection constraints have acted on three core eudicot clades, which might enable paleoduplicated PDAT paralogs to either become nonfunctionalized or develop divergent expression patterns during evolution. Overall, our study provides important insights into the evolution of the plant PDAT gene family and explores the evolutionary mechanism underlying the functional diversification among the core eudicot PDAT paralogs.
Highlights
PHOSPHOLIPID:DIACYLGLYCEROL ACYLTRANSFERASE (PDAT) is an enzyme that catalyzes the transfer of a fatty acyl moiety from the sn-2 position of a phospholipid to the sn-3-position of sn-1,2-diacylglyerol, forming triacylglycerol and a lysophospholipid
To identify PDATs in different plant species, a genome-wide search was performed using both Arabidopsis AthPDAT1 and AthPDAT2 amino acid sequences as queries to BLAST against 40 genomes listed in the Phytozome database
To verify the reliability of BLAST results, these 128 protein sequences were subjected to InterPro and Pfam analysis (Supplemental Table S3), and all of them were classified into the LECITHIN:CHOLESTEROL ACYLTRANSFERASE (LCAT) family (Pfam: 02450)
Summary
PHOSPHOLIPID:DIACYLGLYCEROL ACYLTRANSFERASE (PDAT) is an enzyme that catalyzes the transfer of a fatty acyl moiety from the sn-2 position of a phospholipid to the sn-3-position of sn-1,2-diacylglyerol, forming triacylglycerol and a lysophospholipid. It is worth noting that the PDATmediated TAG-forming mechanism has been detected in the bacterium Streptomyces coelicolor (Arabolaza et al, 2008), but it has no counterpart in mammals These previous studies reveal that (1) PDAT can exist as multiple copies in plant genomes, (2) different PDAT gene paralogs can encode enzymes with different TAGsynthesizing ability, and (3) certain PDATs can have unique substrate selectivity. All these findings shed new light on TAG biosynthetic mechanisms in plants and highlight the need for a deeper understanding of the complexity of plant PDATs. In this study, we have sought to provide further insights into the present-day diversity and ortholog/paralog relationship of plant PDATs via a genome-wide comparative analysis
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