Three genes from Solanum chacoense coding for squalene synthase

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dc.contributor.authorWadlington, William Herringen
dc.contributor.committeememberOkumoto, Sakikoen
dc.contributor.committeememberCollakova, Evaen
dc.contributor.committeememberVeilleux, Richard E.en
dc.contributor.committeememberTokuhisa, James G.en
dc.contributor.departmentHorticultureen
dc.date.accessioned2017-04-04T19:49:42Zen
dc.date.adate2011-11-03en
dc.date.available2017-04-04T19:49:42Zen
dc.date.issued2011-05-04en
dc.date.rdate2016-10-18en
dc.date.sdate2011-08-20en
dc.description.abstractSqualene synthase (EC 2.5.1.2.1; SQS) is located at a branch point in the isoprenoid pathway and catalyzes the condensation of two molecules of farnesyl diphosphate to form squalene. SQS activity contributes to the formation of triterpenes and sterols, including phytosterols, brassinosteroids, cholesterol, and in potato plants, steroidal glycoalkaloids (SGAs). These compounds have diverse functions in the plant. SGAs are defense compounds that deter feeding by potato pests. The wild potato Solanum chacoense accumulates higher amounts of SGAs than cultivated potato and some of its accessions produce leptines, a rare class of SGAs that is toxic to Colorado potato beetle. Unlike most eukaryotes, higher plants have more than one gene coding for SQS. Three sqs gene homologs were isolated from S. chacoense, sqs1Sc, sqs2Sc, and sqs4Sc, that have 74 to 83% identity at the amino acid level. Some of the amino acid differences between sqs isoforms are likely to affect enzyme activity. Each of the three genes contained an intron in the 3'UTR. This feature may have a role in the nonsense-mediated decay of incomplete sqs mRNAs. A partial SQS polypeptide retaining catalytic activity but lacking the membrane anchoring domain could adversely affect a cell with the randomly distributed accumulation of squalene. The mRNA of sqs1Sc and sqs2Sc was detected in all tissues whereas sqs4Sc transcript was limited to bud tissue. The sqs2Sc transcript was less uniformly distributed in the plant than sqs1Sc and accumulated most abundantly in floral tissue. The results demonstrate that the three sqs genes have different patterns of gene expression and encode proteins with different primary structures indicating distinct roles in plant squalene metabolism.en
dc.description.degreeMaster of Scienceen
dc.identifier.otheretd-08202011-082956en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-08202011-082956/en
dc.identifier.urihttp://hdl.handle.net/10919/76849en
dc.language.isoen_USen
dc.publisherVirginia Techen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectsqualene synthasesen
dc.subjectSolanum chacoenseen
dc.subjectgene familyen
dc.titleThree genes from Solanum chacoense coding for squalene synthaseen
dc.typeThesisen
dc.type.dcmitypeTexten
thesis.degree.disciplineHorticultureen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen

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