Stephen H Howell

Distinguished Professor
Stephen Howell photo

Dr. Howell, University Professor in GDCB , received his B.S. in Biology at Grinnell College in 1963 and his Ph.D. in Biology at The Johns Hopkins University, Baltimore, MD in 1967. After completing a NIH postdoctoral fellowship at the University of California San Diego, Dr. Howell became a faculty member at the same institution where he was promoted to Professor in 1982. In 1988, he joined the Boyce Thompson Institute in Ithaca NY and became the Vice-President for Research in 1997. In 2001, Dr. Howell accepted a Professor position and Director of the Plant Sciences Institute at Iowa State University. In 2009, Dr. Howell stepped down as Director of the Plant Sciences Institute and assumed new responsibilities as Division Director of the Division of Molecular and Cellular Biosciences at the National Science Foundation in Washington, D.C. In 2011, Dr. Howell completed his tour of duty with the Foundation and returned to Iowa State to resume his faculty role in the Department.  In 2015 he was named University Professor.

Research Description

Abiotic stresses, such as heat, drought, flooding and salt stress, are the major causes of crop losses worldwide, and, therefore, tolerance to stress is a highly valued crop trait. Stress tolerance has become an even more important trait as demands grow for producing crops for biofuels, particularly, as we face the prospects for climate change. We recently discovered a set of stress transducers located on the endoplasmic reticulum (ER) membranes in Arabidopsis that perceive and transduce several different environmental stresses. One set of stress transducers are ER membrane-associated transcription factors that are activated by proteolysis and relocated to the nucleus in response to stress. Different environmental stresses, such as heat stress and salt stress, activate different transcription factors, and we are studying the basis for that specificity. In addition, we are studying what factors are responsible for untethering the stress transducers from the ER in response to stress, how they are transported from the ER to the Golgi apparatus, how they are proteolytically processed and relocated to the nucleus and how they participate in the formation of transcription complexes to activate target genes.


  • Srivastava, R., Deng, Y., Shah, S., Rao, A.G.and S.H. Howell. (in review) BINDING PROTEIN is a master regulator of the ER stress sensor/transducer bZIP28 in Arabidopsis. Plant Cell.
  • Howell, S.H. (2013) ER stress responses in plants.  Ann Rev of Plant Biol. 64.
  • Liu, Y., Soto Burgos, J., Deng, Y., Srivastava, R., Howell, S.H. and D.C. Bassham. (2012) Degradation of the endoplasmic reticulum by autophagy during ER stress in plants.  Plant Cell. 24:4635-4651.
  • Humbert S, Zhong S, Deng Y, Howell SH and S.J. Rothstein SJ. (2012)  Alteration of the bZIP60/IRE1 pathway affects plant response to ER stress in Arabidopsis thaliana.  PLoS One. 7:e39023.
  • Li, Y., Humbert, S. and S.H. Howell (2012) ZmbZIP60 mRNA is spliced in maize in response to ER stress.  BMC Research Notes 5: 144.
  • Srivastava, R., Chen, Y., Deng, Y., Brandizzi, F., and S.H. Howell (2012) Elements proximal to and within the transmembrane domain mediate the organelle-to-organelle movement of bZIP28 under ER stress conditions.  Plant J. 70:1033-1042.
  • Deng, Y., Humbert, S., Liu, J.-X., Srivastava, R., Steven J. Rothstein, S.J. and S.H. Howell (2011) Heat induces the splicing by IRE1 of a mRNA encoding a transcription factor involved in the unfolded protein response in Arabidopsis, Proceedings of the National Academy of Sciences, USA, 108:7247-7252.
  • Liu, J.-X., Howell, S.H.. 2010. Endoplasmic reticulum protein quality control and its relationship to environmental stress responses in plants.  Plant Cell 22: 782-796.
  • Liu, J.-X., Howell, S.H. 2010.  bZIP28 and NF-Y transcription factors are activated by ER stress and assemble into a transcriptional complex to regulate stress response genes in Arabidopsis. Plant Cell 22: 782-796.
  • Srivastava, R., Liu, J.-X., Guo, H., Yin, Y., Howell, S.H. 2009.  Regulation and processing of a plant peptide hormone, AtRALF23, in Arabidopsis.  Plant J. 59: 930-939.
  • Srivastava, R., Liu, J.-X. and S.H. Howell. 2008. Proteolytic processing of a growth promoting peptide by a subtilisin serine protease in Arabidopsis. Plant Journal 56:219-227.
  • Liu, J.-X., Srivastava, R., Che, P. and S.H. Howell. 2008. Stress-induced expression of an activated form of AtbZIP17 provides protection from salt stress in Arabidopsis. Plant, Cell and Environment 12:1735-1743.
  • Liu, J.-X., Srivastava, R., Che, P. and S.H. Howell. 2007. An ER stress response in Arabidopsis is mediated by proteolytic processing and nuclear relocation of a membrane-associated transcription factor AtbZIP28. Plant Cell 19:4111-4119.
  • Liu, J.-X., Srivastava, R., Che, P. and S.H. Howell. 2007. Salt stress responses in Arabidopsis utilize a signal transduction pathway related to ER stress signaling. Plant Journal 51:897-909.
  • Che, P., Lall, S., Nettleton, D. and S.H. Howell. 2006. Gene expression programs during shoot, root and callus development in Arabidopsis tissue culture. Plant Physiol 141:620-637.
  • Che, P., Love, T.M., Frame, B.R., Wang, K., Carriquiry, A.L. and S.H Howell. 2006. Gene expression patterns during somatic embryo development and germination in maize Hi II callus cultures. Plant Mol. Biol 62:1-14.
  • Ikeda, Y., Banno, H., Niu, Q-W., Howell, S.H. and N.-H. Chua. 2006. ENHANCER OF SHOOT REGENERATION2 gene in Arabidopsis upregulates CUP SHAPE COTYLEDON1 gene expression and controls cotyledon development. Plant Cell Phys 47:1443-1456.
  • DeCook, R., Lall, S., Nettleton, D. and S.H. Howell. 2005. Genetic regulation of gene expression during shoot development in Arabidopsis. Genetics 72:1155-1164.
  • Lall, S., Nettleton, D., DeCook, R., Che, P. and S.H. Howell. 2004. QTLs associated with adventitious shoot formation in tissue culture and the program of shoot development in Arabidopsis. Genetics 167:1883-1892.
  • Hoekenga, O.A., Vision, T.J., Shaff, J.E., Monforte, A.J., Lee, G.P., Howell, S.H. and L. V. Kochian. 2003. Identification and characterization of Al tolerance loci in Arabidopsis.. Plant Physiology 132:936-948.
  • Che, P., Gingerich, D. J., Lall S. and S. H. Howell. 2002. Global and cytokinin-related gene expression changes during shoot development in Arabidopsis. Plant Cell 14:2771-2785.
  • Cary, A. J., P. Che and S.H. Howell. 2002. Developmental events and shoot meristem gene expression patterns during shoot development in Arabidopsis thaliana. Plant J. 32:867-877.
  • S.H. Howell. 1998. Molecular Genetics of Plant Development. Cambridge University Press, Cambridge UK :365.
  • Howell, S.H., Lall, S. and P. Che. 2003. Cytokinins and shoot development.. Trends in Plant Science 8:453-459.
Area of Expertise: 
Stress Tolerance in Plants
B.A., Grinnell College, 1963
Ph.D., Johns Hopkins University
1035A Roy J Carver Co-Lab