Robert Thornburg

Robert Thornburg


  • Plant gene expression
  • Plant/insect interaction
  • Plant development

2212 Molecular Biology Building
Dept. of Biochemistry, Biophysics & Molecular Biology
Iowa State University
Ames, IA 50011

Phone: (515) 294-7885


B.S., Chemistry and Zoology, Univ. of Tennessee – Martin, 1976
Ph.D., Chemistry, University of South Carolina, 1981
Postdoctoral Fellow, UT – San Antonio, 1981-1983
Postdoctoral Fellow, Washington State University, 1983-1986

Research Interests

Dr. Thornburg is interested in the regulation of plant defense genes.  His long-term goals are to understand in molecular terms how plants respond to insect and pathogen attack. Plant responses are mediated by complex signalling pathways, signal transduction, hormones, nuclear factors and probably other unknown activities.  Dr. Thornburg’s goal is to understand the biochemical mechanisms that contribute to expression of these plant defense genes.

When insects attack a plant, the plant has the ability to respond to the attack by inducing a variety of gene products following attack by insects.  We have isolated and characterized several wound-inducible genes from potato that constitute part of the plant’s response to insect attack.  These genes (pin2), which encode proteins termed proteinase inhibitor II, are normally quiescent in the foliage, yet, following insect attack, they are highly expressed.  Our experimental goals are to understand the transcriptional activation of these genes in plant foliage.  To examine this question in some molecular detail, we are using a three-pronged approach.  First, we are examining the early events following wounding.  Second, we are examining the early gene events which are transcriptionally activated.  Third, we are taking a molecular genetic approach to identify mutatations which block wound-induction and pathogen-induction.

As an outgrowth of our work to identify mutations that block wound-induction, we have developed an interest in the metabolism of pyrimidines in plants.  We have isolated cDNAs for the entire pyrimidine biosynthetic pathway, and have some of the genes isolated. Our work here is to understand the mechanisms that regulate the metabolism of this very important biosynthetic pathway in plants.

Selected Publications

1:  Liu G, Thornburg RW. Knockdown of MYB305 disrupts nectary starch metabolism and floral nectar production. Plant J. 2012 May;70(3):377-88. doi: 10.1111/j.1365-313X.2011.04875.x. Epub 2012 Jan 23. PubMed PMID: 22151247.

2:  Hillwig MS, Kanobe C, Thornburg RW, Macintosh GC. Identification of S-RNase and peroxidase in petunia nectar. J Plant Physiol. 2011 May 1;168(7):734-8. doi: 10.1016/j.jplph.2010.10.002. Epub 2010 Nov 18. PubMed PMID: 21093100.

3:  Hillwig MS, Liu X, Liu G, Thornburg RW, Macintosh GC. Petunia nectar proteins have ribonuclease activity. J Exp Bot. 2010 Jun;61(11):2951-65. doi: 10.1093/jxb/erq119. Epub 2010 May 11. PubMed PMID: 20460362; PubMed Central PMCID: PMC2892141.

4:  Liu G, Ren G, Guirgis A, Thornburg RW. The MYB305 transcription factor regulates expression of nectarin genes in the ornamental tobacco floral nectary. Plant Cell. 2009 Sep;21(9):2672-87. doi: 10.1105/tpc.108.060079. Epub 2009 Sep 25. PubMed PMID: 19783761; PubMed Central PMCID: PMC2768911.

5:  Horner HT, Healy RA, Ren G, Fritz D, Klyne A, Seames C, Thornburg RW. Amyloplast to chromoplast conversion in developing ornamental tobacco floral nectaries provides sugar for nectar and antioxidants for protection. Am J Bot. 2007 Jan;94(1):12-24. doi: 10.3732/ajb.94.1.12. PubMed PMID: 21642203.

6:  Carter C, Healy R, O’Tool NM, Naqvi SM, Ren G, Park S, Beattie GA, Horner HT, Thornburg RW. Tobacco nectaries express a novel NADPH oxidase implicated in the defense of floral reproductive tissues against microorganisms. Plant Physiol. 2007 Jan;143(1):389-99. Epub 2006 Nov 17. PubMed PMID: 17114277; PubMed Central PMCID: PMC1761964.

7:  Naqvi SM, Harper A, Carter C, Ren G, Guirgis A, York WS, Thornburg RW. Nectarin IV, a potent endoglucanase inhibitor secreted into the nectar of ornamental tobacco plants. Isolation, cloning, and characterization. Plant Physiol. 2005 Nov;139(3):1389-400. Epub 2005 Oct 21. PubMed PMID: 16244157; PubMed Central PMCID: PMC1283774.

8:  Carter CJ, Thornburg RW. Tobacco Nectarin III is a bifunctional enzyme with monodehydroascorbate reductase and carbonic anhydrase activities. Plant Mol Biol. 2004 Feb;54(3):415-25. PubMed PMID: 15284496.

9:  Carter C, Thornburg RW. Is the nectar redox cycle a floral defense against microbial attack? Trends Plant Sci. 2004 Jul;9(7):320-4. Review. PubMed PMID: 15231276.

10:  Carter CJ, Thornburg RW. Tobacco nectarin V is a flavin-containing berberine bridge enzyme-like protein with glucose oxidase activity. Plant Physiol. 2004 Jan;134(1):460-9. PubMed PMID: 14730073; PubMed Central PMCID: PMC316325.

11:  Carter C, Thornburg RW. The nectary-specific pattern of expression of the tobacco Nectarin I promoter is regulated by multiple promoter elements. Plant Mol Biol. 2003 Mar;51(4):451-7. PubMed PMID: 12650612.

12:  Carter C, Thornburg RW. Tobacco nectarin I. Purification and characterization as a germin-like, manganese superoxide dismutase implicated in the defensE of floral reproductive tissues. J Biol Chem. 2000 Nov 24;275(47):36726-33. PubMed PMID: 10952990.

13:  Carter C, Graham RA, Thornburg RW. Nectarin I is a novel, soluble germin-like protein expressed in the nectar of Nicotiana sp. Plant Mol Biol. 1999 Sep;41(2):207-16. PubMed PMID: 10579488.

14:  Carter C, Graham RA, Thornburg RW. Arabidopsis thaliana contains a large family of germin-like proteins: characterization of cDNA and genomic sequences encoding 12 unique family members. Plant Mol Biol. 1998 Dec;38(6):929-43. PubMed PMID: 9869400.

15:  Chen YL, Park S, Thornburg RW, Tabatabai LB, Kintanar A. Structural characterization of the active site of Brucella abortus Cu-Zn superoxide dismutase: a 15N and 1H NMR investigation. Biochemistry. 1995 Sep 26;34(38):12265-75. PubMed PMID: 7547969.

16:  Xu D, McElroy D, Thornburg RW, Wu R. Systemic induction of a potato pin2 promoter by wounding, methyl jasmonate, and abscisic acid in transgenic rice plants. Plant Mol Biol. 1993 Jul;22(4):573-88. PubMed PMID: 8343596.

17:  Santoso D, Thornburg RW. Isolation and Characterization of UMP Synthase Mutants from Haploid Cell Suspensions of Nicotiana tabacum. Plant Physiol. 1992 Jul;99(3):1216-25. PubMed PMID: 16668991; PubMed Central PMCID: PMC1080605.

18:  Thornburg RW, Li X. Wounding Nicotiana tabacum Leaves Causes a Decline in Endogenous Indole-3-Acetic Acid. Plant Physiol. 1991 Jul;96(3):802-5. PubMed PMID: 16668256; PubMed Central PMCID: PMC1080846.

19:  Huang J, Hack E, Thornburg RW, Myers AM. A yeast mitochondrial leader peptide functions in vivo as a dual targeting signal for both chloroplasts and mitochondria. Plant Cell. 1990 Dec;2(12):1249-60. PubMed PMID: 1967076; PubMed Central PMCID: PMC159970.

20:  Thornburg RW, Kernan A, Molin L. Chloramphenicol Acetyl Transferase (CAT) Protein Is Expressed in Transgenic Tobacco in Field Tests following Attack by Insects. Plant Physiol. 1990 Feb;92(2):500-5. PubMed PMID: 16667304; PubMed Central PMCID: PMC1062320.