Oil accumulation in leaves directed by modification of fatty acid breakdown and lipid synthesis pathways

Abstract

SummaryPlant oils in the form of triacylglycerol (TAG) are used for food, industrial feedstock and biofuel manufacture. Although TAG is typically harvested from the fruit or seeds of oil crop species, plants can also accumulate small amounts of TAG in the leaves and other vegetative tissues. Here we show that leaf TAG levels can be increased significantly (10-20 fold) by blocking fatty acid breakdown, particularly during extended dark treatments or leaf senescence in the model plant Arabidopsis. Generation of a double mutant in fatty acid breakdown and diacylglycerol acyltransferase 1 (DGAT1) resulted in a severe vegetative growth phenotype suggesting that partitioning of fatty acids to TAG in leaves is carried out predominantly by this acyltransferase. LEC2, a seed development transcription factor involved in storage product accumulation, was ectopically expressed during senescence in the fatty acid breakdown mutant COMATOSE (cts2). This resulted in accumulation of seed oil type species of TAG in senescing tissue. Our data suggests that recycled membrane fatty acids can be re-directed to TAG by expressing the seed-programme in senescing tissue or by a block in fatty acid breakdown. This work raises the possibility of producing significant amounts of oil in vegetative tissues of biomass crops such as Miscanthus.

ABI4 Activates DGAT1 Expression in Arabidopsis Seedlings during Nitrogen Deficiency

“…Here, we suggest that there is also a homeostasis between TAG biosynthesis and degradation in higher plants. Experimental evidence has indicated that extended darkness treatment of fatty acid breakdown mutants, such as pxa1, cts2, and acx1acx2, led to the ectopic accumulation of TAG in the leaf (Kunz et al, 2009;Slocombe et al, 2009). The TAG content in naturally senescing leaves of fatty acid breakdown mutants was also increased (Slocombe et al, 2009).…”

“…Experimental evidence has indicated that extended darkness treatment of fatty acid breakdown mutants, such as pxa1, cts2, and acx1acx2, led to the ectopic accumulation of TAG in the leaf (Kunz et al, 2009;Slocombe et al, 2009). The TAG content in naturally senescing leaves of fatty acid breakdown mutants was also increased (Slocombe et al, 2009). These data demonstrated that in the wild-type plants, the ectopically accumulated TAG in leaves is broken down rapidly and proved that a TAG homeostasis exists in higher plants.…”

“…Arabidopsis dgat1 mutant seeds only accumulate about 55% to 75% of TAG (Routaboul et al, 1999;Zou et al, 1999;Kaup et al, 2002), whereas seedspecific overexpression of DGAT1 increases oil content from 11% to 28% (Jako et al, 2001;Taylor et al, 2009;Andrianov et al, 2010). DGAT1 is also important for TAG accumulation in leaves (Slocombe et al, 2009). For instance, DGAT1 is up-regulated in senescing leaves, correlating with the plastid fatty acid partition into TAG (Kaup et al, 2002).…”

The SUGAR-DEPENDENT1 Lipase Limits Triacylglycerol Accumulation in Vegetative Tissues of Arabidopsis

“…However, a number of studies have established that the oil content can be boosted by the overexpression of individual oil biosynthetic enzymes such as ACYL-COENZYME A:DI-ACYLGLYCEROL ACYLTRANSFERASE1 (DGAT1; Bouvier-Navé et al, 2000) or transcriptional "master" regulators that govern the expression of multiple enzymes in the pathway, such as WRINKLED1 (WRI1), LEAFY COTYLDON1 (LEC1), and LEC2 (Cernac and Benning, 2004;Mu et al, 2008;Andrianov et al, 2010;Sanjaya et al, 2011). In addition, several mutants have been identified that exhibit ectopic oil accumulation (Ogas et al, 1997;Xu et al, 2005;Kunz et al, 2009;Slocombe et al, 2009;James et al, 2010). Among these are pxa1 (peroxisomal ABC transporter1) and cgi58 (comparative gene identification-58), which are associated with lipid catabolism.…”

Peroxisome Function, Biogenesis, and Dynamics in Plants

“…Various mutants defective in b-oxidation, the glyoxylate cycle, or NADH reduction display peroxisomes clustered near oil bodies after oil bodies are depleted in wild type (Germain et al, 2001;Eastmond, 2007;Pracharoenwattana et al, 2007;Cassin-Ross and Hu, 2014;Rinaldi et al, 2016). Moreover, diphenyl methylphosphonate confers triacylglycerol retention (Brown et al, 2013) similar to sdp1 and pxa1 mutants (Eastmond, 2006;Slocombe et al, 2009;Kelly et al, 2013). The mechanism through which peroxisomal enzyme dysfunction feeds back to prevents triacylglycerol mobilization is unknown.…”