Potato tuber expression of Arabidopsis WRINKLED1 increase triacylglycerol and membrane lipids while affecting central carbohydrate metabolism

Abstract

SummaryTuber and root crops virtually exclusively accumulate storage products in the form of carbohydrates. An exception is yellow nutsedge (Cyperus esculentus) in which tubers have the capacity to store starch and triacylglycerols (TAG) in roughly equal amounts. This suggests that a tuber crop can efficiently handle accumulation of energy dense oil. From a nutritional as well as economic aspect, it would be of interest to utilize the high yield capacity of tuber or root crops for oil accumulation similar to yellow nutsedge. The transcription factor WRINKLED1 from Arabidopsis thaliana, which in seed embryos induce fatty acid synthesis, has been shown to be a major factor for oil accumulation. WRINKLED1 was expressed in potato (Solanum tuberosum) tubers to explore whether this factor could impact tuber metabolism. This study shows that a WRINKLED1 transcription factor could induce triacylglycerol accumulation in tubers of transformed potato plants grown in field (up to 12 nmol TAG/mg dry weight, 1% of dry weight) together with a large increase in polar membrane lipids. The changes in metabolism further affected starch accumulation and composition concomitant with massive increases in sugar content.

Up‐regulation of lipid biosynthesis increases the oil content in leaves of Sorghum bicolor

“…Starch is a major carbon and energy storage form in leaves and some source tissues such as tubers and therefore expected to compete with lipids for photosynthetic carbon. Previous attempts at engineering elevated levels of storage lipids in a variety of species and tissues did negatively impact transitory or storage starch metabolism (Zale et al ., ; Vanhercke et al ., ; Hofvander et al ., ; Liu et al ., ; Mitchell et al ., ; Vanhercke et al ., ). Quantification of starch levels in transgenic sorghum leaves showed a distinct difference between the two transgenic populations.…”

“…Contrary to the results in A. thaliana and tobacco, achievements in other species thus far remain limited to small increases in TAG or total lipids contents. Examples include ryegrass (Beechey-Gradwell, 2016;Winichayakul et al, 2008), corn (Alameldin et al, 2017), potato (Hofvander et al, 2016;Klaus et al, 2004;Liu et al, 2017), Jatropha curcas (Maravi et al, 2016) and rice (Singh et al, 2016).…”

Characterization of the enzymatic activity and physiological function of the lipid droplet‐associated triacylglycerol lipase AtOBL1

“…For the analysis of free sterols, the extracted lipids of pollen tubes deriving from 5 mg pollen were evaporated under N 2 stream and 20 μl pyridine and 20 μl N ‐methyl‐ N ‐(trimethylsilyl) trifluoroacetamide (MSTFA) was added. The samples were analysed by GC‐MS as described (Hofvander et al ., ), but using an inlet temperature of 230°C and a temperature gradient applied starting with 50°C for 5 min, 50–170°C at 30°C min −1 , 170–325°C at 5°C min −1 and 325°C for 30 min. Helium was used as carrier gas.…”

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

“…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.…”