Comparative and evolutionary analyses of the divergence of plant oligosaccharyltransferase STT3 isoforms

Abstract

STT3 is a catalytic subunit of hetero‐oligomeric oligosaccharyltransferase (OST), which is important for asparagine‐linked glycosylation. In mammals and plants, OSTs with different STT3 isoforms exhibit distinct levels of enzymatic efficiency or different responses to stressors. Although two different STT3 isoforms have been identified in both plants and animals, it remains unclear whether these isoforms result from gene duplication in an ancestral eukaryote. Furthermore, the molecular mechanisms underlying the functional divergences between the two STT3 isoforms in plant have not been well elucidated. Here, we conducted phylogenetic analysis of the major evolutionary node species and suggested that gene duplications of STT3 may have occurred independently in animals and plants. Across land plants, the exon–intron structure differed between the two STT3 isoforms, but was highly conserved for each isoform. Most angiosperm STT3a genes had 23 exons with intron phase 0, while STT3b genes had 6 exons with intron phase 2. Characteristic motifs (motif 18 and 19) of STT3s were mapped to different structure domains in the plant STT3 proteins. These two motifs overlap with regions of high nonsynonymous‐to‐synonymous substitution rates, suggesting the regions may be related to functional difference between STT3a and STT3b. In addition, promoter elements and gene expression profiles were different between the two isoforms, indicating expression pattern divergence of the two genes. Collectively, the identified differences may result in the functional divergence of plant STT3s.

Genome-wide scan for selection signatures reveals novel insights into the adaptive capacity in local North African cattle

“…STT3B is a catalytic subunit of hetero oligomeric oligosaccharyltransferase (OST), which is important for asparagine linked glycosylation. In mammals and plants, OSTs exhibit distinct levels of enzymatic efficiency or different responses to stressors 45 . OSBPL10 gene confers African-ancestry protection against dengue haemorrhagic fever in admixed Cubans 46 .…”

Uncoupling the hydrolysis of lipid-linked oligosaccharide from the oligosaccharyl transfer reaction by point mutations in yeast oligosaccharyltransferase

“…Except for Caenorhabditis species, the genomes from all sequenced metazoan organisms contain two STT3 genes (STT3A and STT3B). Plant genomes also encode two copies of STT3 genes (STT3A and STT3B) (13). In the phylum Protista, for example, the Leishmania major genome contains four stt3 genes, stt3A, stt3B, stt3C, and stt3D (14).…”

“…In the phylum Protista, for example, the Leishmania major genome contains four stt3 genes, stt3A, stt3B, stt3C, and stt3D (14). Despite their similar names, the human, plant, and protist genes lack direct orthologous relationships (13,15). One important exception is fungi, including S. cerevisiae, with genomes encoding a single stt3 gene.…”