Enhanced polyhydroxybutyrate production in transgenic sugarcane

Abstract

Summary Polyhydroxybutyrate (PHB) is a bacterial polyester that has properties similar to some petrochemically produced plastics. Plant‐based production has the potential to make this biorenewable plastic highly competitive with petrochemical‐based plastics. We previously reported that transgenic sugarcane produced PHB at levels as high as 1.8% leaf dry weight without penalty to biomass accumulation, suggesting scope for improving PHB production in this species. In this study, we used different plant and viral promoters, in combination with multigene or single‐gene constructs to increase PHB levels. Promoters tested included the maize and rice polyubiquitin promoters, the maize chlorophyll A/B‐binding protein promoter and a Cavendish banana streak badnavirus promoter. At the seedling stage, the highest levels of polymer were produced in sugarcane plants when the Cavendish banana streak badnavirus promoter was used. However, in all cases, this promoter underwent silencing as the plants matured. The rice Ubi promoter enabled the production of PHB at levels similar to the maize Ubi promoter. The maize chlorophyll A/B‐binding protein promoter enabled the production of PHB to levels as high as 4.8% of the leaf dry weight, which is approximately 2.5 times higher than previously reported levels in sugarcane. This is the first time that this promoter has been tested in sugarcane. The highest PHB‐producing lines showed phenotypic differences to the wild‐type parent, including reduced biomass and slight chlorosis.

Factors affecting polyhydroxybutyrate accumulation in mesophyll cells of sugarcane and switchgrass

“…Sugarcane lines identified in our previous reports are relabelled as follows with PHB values reported earlier [12,13,15] as the mean ± standard error: Wild-type Q117 (WT), TA4 (LP, 0.45 ± 0.02% DW PHB), 4 F1 (MP1, 1.21 ± 0.24% DW PHB), 8C8 (MP2, 1.30 ± 0.11% DW PHB) and 7C3 (HP, 3.11 ± 0.31% DW PHB). These PHB values reflect data measured in whole-leaf blades from the oldest green leaf.…”

“…Although PHB accumulation in the chloroplasts of the C 4 crops maize [14] ( Zea mays L., NADP-ME C 4 subtype), sugarcane [12,13] ( Saccharum sp ., NADP-ME C 4 subtype) and switchgrass [11,15] ( Panicum virgatum L., NAD-ME C 4 subtype) has reached more than 5% of leaf dry weight (DW) in individual leaves, these levels are not yet commercially viable [11]. The highest PHB levels to date have been reported in chloroplasts of C 3 plants upon nuclear expression of plastid-targeted enzymes in Arabidopsis thaliana [18] (up to ~40% DW) or direct expression of transgenes from the plastome in tobacco [19] (up to 18% DW).…”

Tissue-specific transcriptome analysis within the maturing sugarcane stalk reveals spatial regulation in the expression of cellulose synthase and sucrose transporter gene families

“…Due to its rapid growth rate and large biomass yield, sugarcane has also been investigated as a transgenic platform for the production of enzymes and renewable chemicals (McQualter et al 2005;Wang et al 2005;Wu and Birch 2007;Fong Chong et al 2010;Hamerli and Birch 2011;Basnayake et al 2012;Petrasovits et al 2012). Many of these approaches would benefit from an improved knowledge of the compartmentation of metabolic activities.…”

Economic and cradle-to-gate life cycle assessment of poly-3-hydroxybutyrate production from plastic producing, genetically modified hybrid poplar leaves

“…Hybrids (sugarcane). 7,13 While production in plants could prove advantageous in the long run, current yields are far below those found in bacterial cultures. For example, yields in transgenic alfalfa have been reported at just 2.5 Â 10 À3 to 0.18% w/w on a dry weight basis.…”

“…For example, yields in transgenic alfalfa have been reported at just 2.5 Â 10 À3 to 0.18% w/w on a dry weight basis. 12 Sugarcane yields have been reported at up to 4.8% w/w 7,13 and transgenic Arabidopsis has shown potential to produce up to 40% yield. 10 However, a very high accumulation of PHB in transgenic Arabidopsis produced stunted plants with sever metabolic and developmental defects.…”