Abstract
The Arabidopsis has 51 proteins annotated as serine carboxypeptidase-like (SCPL) enzymes. Although biochemical and cellular characterization indicates SCPLs involved in protein turnover or processing, little is known about their roles in plant metabolism. In this study, we identified an Arabidopsis mutant, bis4 (1-butanol insensitive 4), that was insensitive to the inhibitory effect of 1-butanol on seed germination. We cloned the gene that was defective in bis4 and found that it encoded an SCPL41 protein. Transgenic Arabidopsis plants constitutively expressing SCPL41 were generated, oil body staining and lipidomic assays indicated that SCPL41-overexpressing plants showed a decrease in membrane lipid content, especially digalactosyl diglyceride (DGDG) and monogalactosyl diglyceride (MGDG) contents, while the loss of SCPL41 increased the membrane lipid levels compared with those in wild-type plants. These findings suggested that SCPL41 had acquired novel functions in membrane lipid metabolism.
Highlights
Serine carboxypeptidases (SCPs) and serine carboxypeptidase-like (SCPL) proteins compose a large enzyme family that functions in the hydrolysis of the C-terminal peptide bond in proteins or peptides [1,2,3]
Monogalactosyl diglyceride (MGDG) content, while the loss of SCPL41 increased the membrane lipid levels compared with those in wild-type plants. These findings suggest that SCPL41 has novel functions in membrane lipid metabolism
We identified a 1-butanol-insensitive mutant, named bis4 (1-butanol insensitive 4), by screening an ethyl methanesulfonate (EMS)-mutagenized plant pool (Col-0 background) for changes in the percentage of seed germination in the presence of exogenous 1-butanol
Summary
Serine carboxypeptidases (SCPs) and serine carboxypeptidase-like (SCPL) proteins compose a large enzyme family that functions in the hydrolysis of the C-terminal peptide bond in proteins or peptides [1,2,3]. SCPLs share high levels of similarity with SCPs. Arabidopsis has at least 51 members [4], while 71 SCPLs exist in the rice genome [1], indicating functional redundancy among members of the SCPL family. Phylogenetic analysis based on protein sequences shows that the acyltransferase of SCPLs has a single origin within the SCPL family [4,17,22]. Their acyltransferase function may have evolved since the divergence of higher plants from mosses, and their genes have undergone independent diversification in monocot and dicot lineages [22]. One clade consists of 21 members but only two of them are experimentally characterized as acyltransferases in plants’ secondary metabolism: sinapoylglucose:malate sinapoyltransferase and sinapoylglucose:choline sinapoyltransferase [20]
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