Our lab is studying the molecular mechanism(s) of growth control by the plant hormone auxin. Auxins are thought to influence diverse growth responses, such as cell elongation, cell division and cell differentiation.

To elucidate the early molecular events involved in these growth responses, our research has focused on genes that are rapidly modulated in response to exogenous auxin. We have cloned and characterized several classes of soybean sequences that are up-regulated after a brief (two to 15 minutes) exposure to auxin. Within the promoter of one of these genes, we have identified minimal DNA elements that are critical to auxin-inducibility (auxin response elements or AuxREs). Recently, we have characterized a novel family of transcription factors that specifically interact with the AuxRE. Our current goal is to isolate additonal factors involved in auxin-inducible gene expression. In addition, we are taking a genetic approach to identify genes involved in the auxin signal transduction pathway.

• Research team receives Charles Reid Barnes Life Membership Award from the American Society of Plant Biologists (Apr 2009)

• Fellow, American Association for the Advancement of Science (2011)
• Recipient of the Charles Reid Barnes Life Membership Award, American Society of Plant Biologists (2009)

Li H, Hagen G, and Guilfoyle TJ. Do some IAA proteins have two repression domains? Plant Signaling and Behavior 2011;6(6):858-860.

Hagen L, Tiwari SB, Hagen G, and Guilfoyle TJ. Identical amino acid substitutions in the repression domain of auxin/indole-3-acetic acid proteins have contrasting effects on auxin signaling. Plant Physiology 2011;155(3):1252-1263.

Li H, Murphy A, Hagen G, and Guilfoyle TJ. Constitutive repression and activation of auxin    signaling in Arabidopsis.  Plant Physiology 2009;149(3):1277-1288.

Ream TS, Hagg JR, Wierzbicki A, Nicora, CD, Norbeck A, Hagen G, Guilfoyle TJ, Pasa-Tolic L, and Pikaard CS. Subunit compositions of the RNA silencing enzymes, RNA polymerase IV and Pol V reveal their origins as a specialized form of RNA polymerase II.  Mol Cell 2009;33(2), 192-203. 

Guilfoyle TJ and Hagen G. Auxin response factors. Current Opinion in Plant Biology 2007;10:1-8.

Tiwari SB, Wang S, Hagen G, and Guilfoyle TJ. Transfection assays with arabidopsis protoplasts containing integrated reporter genes. In J. Salina and JJ Sanchez-Serrano (Eds.), Methods in Molecular Biology: Arabidopsis Protocols 2006; (pp. 241-249), Totowa, NJ: Humana Press.

Ellis CM, Nagpal P, Young JC, Hagen G, Guilfoyle TJ, and Reed JW. AUXIN RESPONSE FACTOR1 and AUXIN RESPONSE FACTOR2 regulate senescence and floral organ abscission in Arabidopsis thaliana. Development 2005;132:4563-4574.

Nagpal P, Ellis CM, Weber H, Ploense S, Barkawi LS, Guilfoyle TJ, Hagen G, Alonso JM, Cohen JD, Farmer EE, Ecker JR, and Reed JW. Auxin response factors ARF6 and ARF8 promote jasmonic acid production and flower maturation. Development 2005;132:4107-4118.

Wilmoth JC, Wang S, Tiwari SB, Joshi AD, Hagen G, Guildoyle TJ, Alonso JM, Ecker JR, and Reed JW. NPH4/ARF7 and ARF19 promote leaf expansion and auxin-induced lareral root formation. Plant J 2005; 43:118-130.

Wang S, Tiwari SB, Hagen G, and Guilfoyle TJ. AUXIN RESPONSE FACTOR7 restores the expression of auxin-responsive genes in mutant arabidopsis leaf mesophyll protoplasts. Plant Cell 2005;17:1979-1993.

Tiwari SB, Wang S, Hagen G, and Guilfoyle TJ. Transfection assays with arabidopsis protoplasts containing integrated reporter genes. In J Silinas and JJ Sanchez-Serrano, Methods in Molecular Biology: Arabidopsis Protocols 2005;(pp. 241-249), Totowa, NJ: Humana Press.

Hagen G, Guilfoyle TJ, and Gray WM. Auxin signal transduction. In PJ Davies (Ed), Plant Hormones 2004; (pp. 282-303), Dordrecht: Kluwer Academic Publishers.

Saito Y, Yamasaki S, Fujii N, Hagen G, Guilfoyle T, and Takahashi H. Isolation of cucumber CsARF cDNAs and expression of the corresponding mRNAs during gravity-regulated morphogenesis of cucumber seedlings. J Exp Bot 2004;55:1315-23.

Hardtke CS, Ckurshumova W, Vidaurre DP, Singh SA, Stamatiou G, Tiwari SB, Hagen G, Guilfoyle TJ, and Berleth T. Overlapping and non-redundant functions of the arabidopsis auxin response factors MONOPTEROS and NONPHOTOTROPIC HYPOCOTYL. Development 2004; 131:1089-1100.

Tiwari SB, Hagen G, and Guilfoyle T. Aux/IAA proteins contain a potent transcriptional repression domain. Plant Cell 2004;16:533-43.

Tiwari SB, Hagen G, and Guilfoyle T. The roles of auxin response factor domains in auxin-responsive transcription. Plant Cell 2003;15:533-43.