A Synergistic Genetic Engineering Strategy Induced Triacylglycerol Accumulation in Potato (Solanum tuberosum) Leaf

Abstract

Potato is the 4th largest staple food in the world currently. As a high biomass crop, potato harbors excellent potential to produce energy-rich compounds such as triacylglycerol as a valuable co-product. We have previously reported that transgenic potato tubers overexpressing WRINKLED1, DIACYLGLYCEROL ACYLTRANSFERASE 1, and OLEOSIN genes produced considerable levels of triacylglycerol. In this study, the same genetic engineering strategy was employed on potato leaves. The overexpression of Arabidopsis thaliana WRINKED1 under the transcriptional control of a senescence-inducible promoter together with Arabidopsis thaliana DIACYLGLYCEROL ACYLTRANSFERASE 1 and Sesamum indicum OLEOSIN driven by the Cauliflower Mosaic Virus 35S promoter and small subunit of Rubisco promoter respectively, resulted in an approximately 30-fold enhancement of triacylglycerols in the senescent transgenic potato leaves compared to the wild type. The increase of triacylglycerol in the transgenic potato leaves was accompanied by perturbations of carbohydrate accumulation, apparent in a reduction in starch content and increased total soluble sugars, as well as changes of polar membrane lipids at different developmental stages. Microscopic and biochemical analysis further indicated that triacylglycerols and lipid droplets could not be produced in chloroplasts, despite the increase and enlargement of plastoglobuli at the senescent stage. Possibly enhanced accumulation of fatty acid phytyl esters in the plastoglobuli were reflected in transgenic potato leaves relative to wild type. It is likely that the plastoglobuli may have hijacked some of the carbon as the result of WRINKED1 expression, which could be a potential factor restricting the effective accumulation of triacylglycerols in potato leaves. Increased lipid production was also observed in potato tubers, which may have affected the tuberization to a certain extent. The expression of transgenes in potato leaf not only altered the carbon partitioning in the photosynthetic source tissue, but also the underground sink organs which highly relies on the leaves in development and energy deposition.

The Diapause Lipidomes of Three Closely Related Beetle Species Reveal Mechanisms for Tolerating Energetic and Cold Stress in High-Latitude Seasonal Environments

“…Finally we note that the MB showed a much higher TAG DBI than the other two species from the outset. This could be due to the very high 18:3n-3 contents of mint leaves (Rao and Lakshminarayana, 1988;Xu et al, 2020) consumed by the MB, which likely explained the high proportions of the TAG species 54:9 (3 × 18:3) and consequently, the high overall TAG DBI.…”

Sorghum bicolorcultivars have divergent and dynamic gene regulatory networks that control the temporal expression of genes in stem tissue

“…Other proof-of-concept studies for increasing TAGs in vegetative tissues have been performed in Arabidopsis thaliana, Brachypodium distachyon, Nicotiana benthamiana, Nicotiana tabacum , sugarcane ( Saccharum spp. ), and Sorghum bicolor (Thelen and Ohlrogge, 2002; Fan, Yan and Xu, 2013; Vanhercke et al , 2013, 2019; Yang et al , 2015; Zale et al , 2016; Mitchell et al , 2020; Parajuli et al , 2020; Xu et al , 2020). For example, in engineered sugarcane, TAGs accumulated to an average of 8.0% of the dry weight of leaves and 4.3% of the dry weight of stems (Huang, Long and Singh, 2015; Zale et al , 2016; Parajuli et al , 2020).…”

“…Another study in tobacco achieved TAGs accumulation up to 19% of the dry weight of the total biomass production by over-expressing the genes encoding WRINKLED1, DGAT, and oleosins (Vanhercke et al , 2014; Zale et al , 2016). However, many of these engineering efforts to increase TAG accumulation in immature vegetative tissues have resulted in negative impacts on plant growth as observed in sorghum, potato, tobacco, and Arabidopsis (Slocombe et al , 2009; Feltus and Vandenbrink, 2012; Kelly et al , 2013; Vanhercke et al , 2014, 2019; Hofvander et al , 2016; Liu et al , 2017; Ramšak et al , 2018; Xiaoyu Xu et al , 2019; Xu et al , 2020; Mitchell et al , 2020). One hypothesis is that driving lipid accumulation under the control of tissue- and/or developmental-stage specific promoters, specifically those active during late development (Moyle and Birch, 2013; Mudge et al , 2013), will have less of an impact on photosynthetic efficiencies and plant growth than constitutive overexpression of genes of interest.…”

Elucidation of Triacylglycerol Overproduction in the C4 Bioenergy Crop Sorghum bicolor by Constraint-Based Analysis

“…This way, by engineering TAG synthesis to only be activated in the final stage of the crop life cycle, transgenic growth penalties could be largely avoided. The late onset of TAG synthesis could be achieved, for example, by chemical induction ( Caddick et al, 1998 ) or using senescence related promoters ( Kim et al, 2015 ; Vanhercke et al, 2017 ; Xu et al, 2020 ). For example, it is known for some species, that ectopic over-expression of the transcription factor WRI1 can cause perturbations in vegetative development ( Marchieve et al, 2014 ).…”