Edited by Miguel De la RosaKeywords: DGAT2 Fatty acid Yeast Triacylglycerol Phaeodactylum tricornutum a b s t r a c t Diacylglycerol acyltransferase (DGAT) plays a pivotal role in triacylglycerol (TAG) formation in some oleaginous organisms. We describe here the identification of a type 2 DGAT (PtDGAT2B) in the diatom Phaeodactylum tricornutum that contains four putative type 2 acyl-CoA:DGATs, sharing little sequence similarity with each other. TAG synthesis and lipid body formation could be completely restored in a Saccharomyces cerevisiae TAG-deficient quadruple mutant by expressing PtDGAT2B. Up-regulation of PtDGAT2B precedes the accumulation of TAG. Functional analysis of enzyme activity in vivo demonstrated that expression of PtDGAT2B can increase the proportion of unsaturated C 16 and C 18 fatty acids in yeast TAG.
High-yield cultivars are characterized by erect leaf canopies that optimize photosynthesis and thus favor increased biomass. Upward curling of the leaf blade (called rolled leaf) can result in enhanced erect-leaf habit, increase erect duration and promote an overall erect leaf canopy. The rice mutant R05, induced through transferred DNA (T-DNA) insertion, had the rolled-leaf trait. The leaves in the wild type demonstrated natural drooping tendencies, resulting in decreasing leaf erection indices (LEIs) during senescence at the 20th day after flowering. Conversely, LEIs of the leaves in R05 remained high, even 20-day post-flowering. We applied T-DNA tagging and isolated a rolled-leaf gene from rice which, when over-expressed, could induce upward curling of the leaf blade. This gene encodes for a protein of 1,048 amino acids including the PAZ and PIWI conserved domains, belonging to the Argonaute (AGO) family. There are at least 18 members of the AGO family in rice. According to high-sequence conservation, the rolled-leaf gene in rice could be orthologous to the Arabidopsis ZIP/Ago7 gene, so we called it OsAGO7. These results provide a possible opportunity for implementing OsAGO7 gene in crop improvement.
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