title: Over-expression of the cucumber expansin gene (Cs-EXPA1) in transgenic maize seed for cellulose deconstruction.
abstract: 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.
authors.affiliation: Arkansas Biosciences Institute, State University, AR, 72467, USA.|Department of Plant Sciences, University of California, Davis, CA, 95616, USA.
authors.forename: Sangwoong
authors.initials: S
authors.lastname: Yoon
authors.affiliation: Department of Biological Sciences, East Tennessee State University, Johnson City, TN, 37614, USA.
authors.forename: Shivakumar P
authors.initials: SP
authors.lastname: Devaiah
authors.affiliation: Department of Mathematics, Arkansas State University, State University, AR, 72467, USA.
authors.forename: Seo-eun
authors.initials: SE
authors.lastname: Choi
authors.affiliation: Department of Veterinary Physiology and Pharmacology, Texas A&M University, College Station, TX, 77845, USA.
authors.forename: Jeff
authors.initials: J
authors.lastname: Bray
authors.affiliation: , 1017 Shadowood Dr., Bryan, TX, 77803, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Love
authors.affiliation: Hannah Engineering, College Station, TX, 77845, USA.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Lane
authors.affiliation: , 712 Encinas Place, College Station, TX, 77845, USA.
authors.forename: Carol
authors.initials: C
authors.lastname: Drees
authors.affiliation: Applied Biotechnology Institute, San Luis Obispo, CA, 93407, USA.
authors.forename: John H
authors.initials: JH
authors.lastname: Howard
authors.affiliation: College of Agriculture and Technology and Arkansas Biosciences Institute, Arkansas State University, PO Box 639, State University, AR, 72467, USA. ehood@astate.edu.
authors.forename: Elizabeth E
authors.initials: EE
authors.lastname: Hood
mesh_terms: D018533:Biomass; D002482:Cellulose / Q000378:metabolism; D018553:Cucumis sativus / Q000235:genetics*; D018506:Gene Expression Regulation, Plant; D010940:Plant Proteins / Q000096:biosynthesis / Q000235:genetics*; D030821:Plants, Genetically Modified; D012639:Seeds / Q000235:genetics*; D003313:Zea mays / Q000235:genetics* / Q000254:growth & development
chemical_list: D010940:Plant Proteins; C095825:expansin protein, plant; D002482:Cellulose
keywords: Cucumber expansin; Expansin assay; Over-expression; Transgenic maize