Abstract
Triacylglycerol is a major component of vegetable oil in seeds and fruits of many plants, but its production in vegetative tissues is rather limited. It would be intriguing and important to explore any possibility to expand current oil production platforms, for example from the plant vegetative tissues. By expressing a suite of transgenes involved in the triacylglycerol biosynthesis, we have previously observed substantial accumulation of triacylglycerol in tobacco (Nicotiana tabacum) leaf and potato (Solanum tuberosum) tuber. In this study, simultaneous RNA interference (RNAi) downregulation of ADP-glucose pyrophosphorylase (AGPase) and Sugar-dependent1 (SDP1), was able to increase the accumulation of triacylglycerol and other lipids in both wild type potato and the previously generated high oil potato line 69. Particularly, a 16-fold enhancement of triacylglycerol production was observed in the mature transgenic tubers derived from the wild type potato, and a two-fold increase in triacylglycerol was observed in the high oil potato line 69, accounting for about 7% of tuber dry weight, which is the highest triacylglycerol accumulation ever reported in potato. In addition to the alterations of lipid content and fatty acid composition, sugar accumulation, starch content of the RNAi potato lines in both tuber and leaf tissues were also substantially changed, as well as the tuber starch properties. Microscopic analysis further revealed variation of lipid droplet distribution and starch granule morphology in the mature transgenic tubers compared to their parent lines. This study reflects that the carbon partitioning between lipid and starch in both leaves and non-photosynthetic tuber tissues, respectively, are highly orchestrated in potato, and it is promising to convert low-energy starch to storage lipids via genetic manipulation of the carbon metabolism pathways.
Highlights
Oil and fats, in the major form of triacylglycerols (TAGs), are one of the most energy-dense compounds in nature (Sanjaya et al, 2011)
wild type (WT) potato and the HO69 were simultaneously transformed with a construct harboring a RNA interference (RNAi) cassette simultaneously targeting the downregulations of StAGPase and StSDP1 expression driven by the CaMV-35S promoter
We have shown that the simultaneous downregulation of StAGPase and StSDP1 induced significant reconstitution in the carbon partitioning in potato vegetative tissues
Summary
In the major form of triacylglycerols (TAGs), are one of the most energy-dense compounds in nature (Sanjaya et al, 2011). A similar result was not observed in potato tubers by repressing the same gene as the content of total fatty acids was barely changed despite considerable reduction in starch accumulation (Klaus et al, 2004) This suggests the possible necessity to co-regulate AGPase together with other genes involved in the lipid metabolism in order to enhance lipids accumulation in potato tubers. Through RNAi downregulation of SDP1 expression in the high oil transgenic tobacco (Nicotiana tabacum) expressing AtWRI1-AtDGAT1- sesame (Sesamum indicum) OLEOSIN1 (SiOLEOSIN1), TAG accumulation was doubled from 15% to 30% of leaf DW compared to the original transgenic line (Vanhercke et al, 2017) These studies demonstrate the possibility to further enhance oil accumulation in plant vegetative tissues by diverting more carbon away from starch and towards lipid biosynthesis, whilst preventing TAG turnover from lipase activity. With a particular focus on the carbohydrate and lipid metabolisms, the conversion of relatively low-energy starch to the energy-dense storage lipids was realized in potato tubers through these genetic engineering approaches, which may provide insight and further advance our understanding of the carbon reallocation and equilibration in plant biomass tissues
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
