Genetic enhancement of oil content in potato tuber (Solanum tuberosum L.) through an integrated metabolic engineering strategy

Abstract

SummaryPotato tuber is a high yielding food crop known for its high levels of starch accumulation but only negligible levels of triacylglycerol (TAG). In this study, we evaluated the potential for lipid production in potato tubers by simultaneously introducing three transgenes, including WRINKLED 1 (WRI1), DIACYLGLYCEROL ACYLTRANSFERASE 1 (DGAT1) and OLEOSIN under the transcriptional control of tuber‐specific (patatin) and constitutive (CaMV‐35S) promoters. This coordinated metabolic engineering approach resulted in over a 100‐fold increase in TAG accumulation to levels up to 3.3% of tuber dry weight (DW). Phospholipids and galactolipids were also found to be significantly increased in the potato tuber. The increase of lipids in these transgenic tubers was accompanied by a significant reduction in starch content and an increase in soluble sugars. Microscopic examination revealed that starch granules in the transgenic tubers had more irregular shapes and surface indentations when compared with the relatively smooth surfaces of wild‐type starch granules. Ultrastructural examination of lipid droplets showed their close proximity to endoplasmic reticulum and mitochondria, which may indicate a dynamic interaction with these organelles during the processes of lipid biosynthesis and turnover. Increases in lipid levels were also observed in the transgenic potato leaves, likely due to the constitutive expression of DGAT1 and incomplete tuber specificity of the patatin promoter. This study represents an important proof‐of‐concept demonstration of oil increase in tubers and provides a model system to further study carbon reallocation during development of nonphotosynthetic underground storage organs.

Ectopic expression of EuWRI1, encoding a transcription factor in E. ulmoides, changes the seeds oil content in transgenic tobacco

“…This was consistent with previous observation that the up‐regulation of fatty acid biosynthesis in tobacco leaves led to substantial reduction in starch accumulation . Also, the over‐expression of AtWRI1 gene resulted in increased oil content in potato tuber, with a concomitant reduction in starch content . This specific reduction of starch might be attributed to the WRI1's ability to shift the carbon flux from starch to lipid synthesis in plants .…”

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

“…In addition, we observed varying degrees of sterility amongst the transgenic lines, possibly as a result of multiple transgene insertions. We therefore performed a detailed analysis on vegetatively propagated tillers obtained from selected primary transformants, similarly to earlier work in sugarcane and potato (Liu et al ., ; Zale et al ., ). To this end, tillers were propagated allowing for triplicate analyses of TAG and TFA levels.…”

Increase in lysophosphatidate acyltransferase activity in oilseed rape (Brassica napus) increases seed triacylglycerol content despite its low intrinsic flux control coefficient

“…diacylglycerol acyltransferase (DGAT); Weselake et al, 2008;Taylor et al, 2009), increasing carbon supply for lipid assembly (Cernac & Benning, 2004;Liu et al, 2010), expanding the time period for rapid oil accumulation (Kanai et al, 2016) or combining a number of gene manipulations to expand the 'push/ (Meyer & Kinney, 2009;Vanhercke et al, 2013;Marillia et al, 2015) to include other constraining factors (e.g. Liu et al, 2017;Vanhercke et al, 2017).…”