Genetic Improvement of Switchgrass Cell Wall Content, Leaf Angle and Flowering Time

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dc.contributor.authorXu, Binen
dc.contributor.committeechairZhao, Bingyuen
dc.contributor.committeememberMei, Chuanshengen
dc.contributor.committeememberPereira, Andyen
dc.contributor.committeememberVeilleux, Richard E.en
dc.contributor.committeememberVinatzer, Boris A.en
dc.contributor.departmentHorticultureen
dc.date.accessioned2017-04-06T15:42:52Zen
dc.date.adate2011-07-25en
dc.date.available2017-04-06T15:42:52Zen
dc.date.issued2011-06-10en
dc.date.rdate2016-10-18en
dc.date.sdate2011-06-24en
dc.description.abstractSwitchgrass (Panicum virgatum L.) is a candidate bioenergy crop. Somatic embryogenic (SE) calli are used for genetic transformation in switchgrass. A superior switchgrass line, HR8, was developed using recurrent tissue culture selection from cv. Alamo. HR8 SE calli were genetically transformable using Agrobacterium at an efficiency of ~12%. We used HR8 somatic embryogenic calli for genetic improvement of switchgrass. The lignin content of feedstock has been proposed as one key trait impacting biofuel production. 4-Coumarate: Coenzyme A ligase (4CL) is one of the key enzymes involved in the monolignol biosynthetic pathway. Two homologous 4CL genes, Pv4CL1 and Pv4CL2, were identified in switchgrass. Gene expression patterns and enzymatic activity assays suggested that Pv4CL1 is involved in monolignol biosynthesis. Stable transgenic plants were obtained with Pv4CL1 down-regulated. RNA interference of Pv4CL1 reduced extractable 4CL activity by 80%, leading to a reduction in lignin content with decreased guaiacyl unit composition. The transgenic plants had uncompromised biomass yield. After dilute acid pretreatment, the low lignin transgenic biomass had significantly increased cellulose hydrolysis (saccharification) efficiency for biofuel production. Erect leaf is a desirable trait to adjust the overall plant architecture to perceive more solar energy and thereby to increase the plant biomass production in a field population. We overexpressed an Arabidopsis NAC transcriptional factor gene, LONG VEGETATIVE PHASE ONE (AtLOV1), in switchgrass. Surprisingly, AtLOV1 induced smaller leaf angle by changing morphologies of epidermal cells in the leaf collar region, affecting lignin content and monolignol composition, and also causing delayed flowering time in switchgrass. Global gene-expression analysis of AtLOV1 transgenic plants demonstrated an array of genes has altered expressions. Potential downstream genes involved in the pleiotropic phenotypic traits of the transgenic plants are discussed.en
dc.description.degreePh. D.en
dc.identifier.otheretd-06242011-111844en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-06242011-111844/en
dc.identifier.urihttp://hdl.handle.net/10919/77118en
dc.language.isoen_USen
dc.publisherVirginia Techen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectPanicum virgatum L.en
dc.subjectGenetic transformationen
dc.subjectLigninen
dc.subjectLeaf angleen
dc.subjectFlowering timeen
dc.titleGenetic Improvement of Switchgrass Cell Wall Content, Leaf Angle and Flowering Timeen
dc.typeDissertationen
dc.type.dcmitypeTexten
thesis.degree.disciplineHorticultureen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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