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Transgenic Res. 2016 Apr;25(2):173-86. doi: 10.1007/s11248-015-9925-1. Epub 2015 Dec 28.

Over-expression of the cucumber expansin gene (Cs-EXPA1) in transgenic maize seed for cellulose deconstruction.

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Arkansas Biosciences Institute, State University, AR, 72467, USA.
Department of Plant Sciences, University of California, Davis, CA, 95616, USA.
Department of Biological Sciences, East Tennessee State University, Johnson City, TN, 37614, USA.
Department of Mathematics, Arkansas State University, State University, AR, 72467, USA.
Department of Veterinary Physiology and Pharmacology, Texas A&M University, College Station, TX, 77845, USA.
, 1017 Shadowood Dr., Bryan, TX, 77803, USA.
Hannah Engineering, College Station, TX, 77845, USA.
, 712 Encinas Place, College Station, TX, 77845, USA.
Applied Biotechnology Institute, San Luis Obispo, CA, 93407, USA.
College of Agriculture and Technology and Arkansas Biosciences Institute, Arkansas State University, PO Box 639, State University, AR, 72467, USA.


Plant cell wall degradation into fermentable sugars by cellulases is one of the greatest barriers to biofuel production. Expansin protein loosens the plant cell wall by opening up the complex of cellulose microfibrils and polysaccharide matrix components thereby increasing its accessibility to cellulases. We over-expressed cucumber expansin in maize kernels to produce enough protein to assess its potential to serve as an industrial enzyme for applications particularly in biomass conversion. We used the globulin-1 embryo-preferred promoter to express the cucumber expansin gene in maize seed. Expansin protein was targeted to one of three sub-cellular locations: the cell wall, the vacuole, or the endoplasmic reticulum (ER). To assess the level of expansin accumulation in seeds of transgenic kernels, a high throughput expansin assay was developed. The highest expressing plants were chosen and enriched crude expansin extract from those plants was tested for synergistic effects with cellulase on several lignocellulosic substrates. Activity of recombinant cucumber expansin from transgenic kernels was confirmed on these pretreated substrates. The best transgenic lines (ER-targeted) can now be used for breeding to increase expansin expression for use in the biomass conversion industry. Results of these experiments show the success of expansin over-expression and accumulation in transgenic maize seed without negative impact on growth and development and confirm its synergistic effect with cellulase on deconstruction of complex cell wall substrates.


Cucumber expansin; Expansin assay; Over-expression; Transgenic maize

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