Harry (Jack) Horner

University Professor Emeritus
Harry Horner photo

Dr. Horner, University Professor, received his B.A., M.S., and Ph.D. from Northwestern University, Evanston, Illinois. Dr. Horner came to Iowa State University in Fall 1964 as an NIH Postdoctoral Fellow. He joined the faculty in 1966. After a series of promotions, Dr. Horner was awarded a University Professorship in 1995 for his creation of the undergraduate Biological/PreMedical Illustration Major. From 1970 to the present, he has served as Director of the Microscopy and NanoImaging Facility (formerly the Bessey Microscopy Facility), a center for Life Sciences and Biotechnology Research and Teaching. He has taught both undergraduate courses in plant and general biology, and a series of graduate-level courses in microscopy that have been replaced with an Individual Module Teaching program. Dr. Horner has served terms as President and Treasurer of the Botanical Society of America, and President and Treasurer of the Iowa Academy of Science. Dr. Horner received the 2004 Botanical Society of America Merit (Distinguished Fellow) Award, the society’s highest honor. In August 2006, he received the Centennial Award from the same Society.  He is also a Distinguished Fellow of the Iowa Academy of Science.

Research Description

His research interests encompass the development and cell biology of male sterility in various crop plants, including soybean and Arabidopsis; the distribution, initiation and development of calcium oxalate crystals in a variety of higher plants and fungi, and most recently in members of the Piperales; and the development and function of floral nectaries in soybean and tobacco. These three diverse research areas are of both theoretical and practical importance and are done in collaboration with researchers at ISU, industry, Germany and Mexico.


  • Karabourniotis G, HT Horner, P Bresta, D Nikolopoulos,G Liakopoulos.  2020.  New insights on the functions of carbon-calcium-inclusions in plants. New Phytologist 228: 845-854. doi:10.1111/NPH.16763 

  • Chatt, EC, S-N Mahalim, N-A Mohd-Fadzil, Rl Roy, PM. Klinkenberg, HT. Horner, M , CJ Carter, BJ Nikolau. 2021.  Systems analyses of key metabolic modules of floral and extrafloral nectaries of cotton (Gossypium hirsutum). Plant Physiology 185: 1595-1616.

  • Healy RA, HT Horner, G Bonito, DJ McLauglin and ME Smith. 2018. An ultrastructural study of spore wall development and septal pores in species of the Pachyphlodes (Pezizaceae, Pezizales) lineage with a description of the new species Pachyphlodes anagardnerii. Mycological Progress 17:45–63 (doi.org/10.1007/s11557-017-1348-3).

  • Thilges K, MA Chamberlin, MC Albertsen and HT Horner. 2017. Microscopic characterization transposon-induced male-sterile, female-sterile mutant in Glycine max L. International Journal of Plant Sciences 178(8):629-638 (DOI: 1086/693857).

  • Horner, HT, S Wanke, B Oelschlägel and M-S Samain. 2017. Peruvian window-leaved Peperomias display unique crystal macropatterns in high-altitude environments. International Journal of Plant Sciences 178(2): 157-167. (DOI: 10.1086/689281).

  • Deng,Y, R Srivastava, TD Quilichini, H Dong, HT Horner and SH Howell. 2016. IRE1, a component of the unfolded protein response signaling pathway, protects pollen development in Arabidopsis from heat stress. The Plant Journal 88: 193–204 (DOI: 10.1111/tpj.13239).

  • Mbofung, G-CY, HT Horner, J Sernett and AE Robertson. 2016. Comparison of susceptible and resistant maize hybrids to colonization by Clavibacter michiganensis subsp. nebraskensisPlant Disease 100(4): 711-717.

  • Au, Carmen, Tong Wang, Acevedo, Nuria and Horner, Harry. 2015. Determination of the gelation mechanism of freeze-thawed hen egg yolk. Journal of Agricultural and Food Chemistry 63 (46):10170–10180 (DOI: 10.1021/acs.jafc.5b04109).

  • Horner, HT, M-S Samain S Wagner and S Wanke. 2015. Towards uncovering evolution of lineage-specific calcium-oxalate crystal patterns in Piperales. BOTANY 93: 159–169 (dx.doi.org/10.1139/cjb-2014-0191).

  • Raman, V, HT Horner and IA Khan. 2014. New and unusual forms of calcium oxalate raphide crystals in the plant kingdom. Journal of Plant Research 127:721-730. DOI 10.1007/s10265-014-0654-y

  • Ott, A, Y Yang, M Bhattacharyya, HT Horner and RG Palmer. 2013. Molecular mapping of D1, D2 and ms5 revealed linkage between the cotyledon color locus D2 and male-sterile locus ms5 in soybean. Plants 2:441-454; doi:10.3390/plants2030441

  • Horner, HT.  2012. Unusual pit fields in lowermost hypodermal cell walls and uppermost walls of photosynthetic crystal-containing palisade parenchyma cells in Peperomia obtusifolia leaves. Annals of Botany 109: 1307-1315 (Cover Photo).

  • Horner, HT, S Wanke and M.-S. Samain. 2012. A comparison of leaf crystal macropatterns in the two sister genera Piper and Peperomia (Piperaceae). American Journal of Botany 99: 983-997.

  • Lersten, NR, and HT Horner. 2011. Unique calcium oxalate “duplex” and “concretion” idioblasts in leaves of tribe Naucleeae (Rubiaceae). Amercian Journal of Botany 94(1): 1-11 (Cover Photo)

  • Jian H, HT Horner, T Pepper, M Blanco, M Campbell and Jay-Lin Jane.  2010.  Formation of elongated starch granules in high-amylose maize.  Carbohydrates Research (12-JAN-2010 DOI information: 10.1016/j.carbpol.2009.12.016).

  • Cover Photo on Science [11 December 2009, Vol. 326 (5959): 1445-1576]. Cover legend – Viewed from the inside of a fractured rice leaf, cells of the rice pathogenic bacterium Xanthomonas oryzae pv. oryzicola invade through a stoma. Xanthomonas species inject host cells with unusual DNA binding proteins called transcription activator-like (TAL) effectors to up-regulate genes important for infection. Two studies in this issue (pages 1501 and 1509; related Perspective, page 1491) decipher TAL effector target specificity and show that new specificities can be engineered. Image: Adam Bogdanove and Harry Horner/Iowa State University; false color: Yael Kats/Science.

  • Lersten, NR, and HT Horner.  2009.  Crystal diversity and macropatterns in leaves of Oleaceae.  Plant Systematics and Evolution 282: 87-102

  • Cervantes-Martinez, I, D Sandhu, M Xu, E Ortiz-Perez, KK Kato, HT Horner, RG Palmer.  2009.  The male sterility locus ms3 is present in a fertility controlling gene cluster in soybean.  Journal of Heredity 100: 565-570.

  • Butterworth, KM, DC Adams, HT Horner and JF Wendel. 2009.  Initiation and early development of fibers in wild and cultivated cotton.  International Journal of Plant Sciences 170:561-574.

  • Healy, R, RG Palmer, and HT Horner.  2009.  Secretory trichome development on gynoecia of soybean and related taxa. International Journal of Plant Sciences 170: 444-456.

  • Horner, HT, S Wanke, and M.-S. Samain.  2009.  Evolution and systematic value of leaf crystal macropatterns: a phylogenetic approach in the genus Peperomia (Piperaceae).  International Journal of Plant Sciences 170: 343-354. (Cover Photo)

  • Wang, X, R Arora, HT Horner, and SL Krebs.  2008.  Structural adaptations in overwintering leaves of thermonastic and non-thermonastic Rhododendron species. Journal of American Society for Horticultural Science 133:768-776. (Cover Photo)

  • Lersten, NR, and HT Horner. 2008.   Subepidermal idioblasts and crystal       macropattern in leaves of Ticodendron (Ticodendraceae).  Plant Science and Evolution 276:255-260.

  • Ortiz-Perez E, RMA Mian, RL Cooper, T Mendiola, J Tew, HT Horner, S J Hanlin, RG Palmer . 2008. Seed-set evaluation of four male-sterile, female-fertile soybean lines using alfalfa leafcutting bees and honey bees as pollinators.Journal of Agricultural Science 146:461-469.

  • Ortiz-Perez E, H Wiley, HT Horner, WH. Davis, RG Palmer. 2008. Insect-mediated cross-pollination in soybean [ Glycine max (L.) Merrill]: II.  Phenotypic recurrent selection. Euphytica 162:269-280.

  • Lersten, NR, and HT Horner.  2008. Crystal macropatterns in leaves of Fagaceae and Nothofagaceae: a comparative study. Plant Systematics and Evolution 271: 239-253.

  • Ren G, RA Healy, HT Horner, MG James and RW Thornburg.  2007.  Expression of starch metabolic genes in the developing nectaries of ornamental tobacco plants.  Plant Science 173:621-637.

  • Ren, G, R A Healy, AM Klyne, HT Horner, MG James, and RW Thornburg.  2007. Transient starch metabolism in ornamental tobacco floral nectaries regulates  nectar composition and release.  Plant Science 173: 277-290.

  • Lersten, NR, and HT Horner.  2007.  Calcium oxalate crystals in tribe Galegeae (Leguminosae) including foliar crystal macropattern development in Caragana frutexCanadian Journal of Botany 85: 394-403.

  • Cervantes-Martinez, I, M Xu, L Zhang, KK Kato, HT Horner, and RG Palmer. 2007. Molecular mapping of male-sterility loci ms2 and ms9 in soybean. Crop Science 47:374-379.

  • Ortiz-Peréz, E, SR Cianzio, H Wiley, HT Horner, WH Davis, and RG Palmer. 2007. Insect-mediated cross-pollination in soybean [GLycine max (L.) Merrill]: I. Agronomic performance. Field Crops Research 101:259-268.

  • Horner, HT, RA Healy, G Ren, D Fritz, A Klyne, C Seames, and RW Thornburg. 2007. Amyloplast to chromoplast conversion provides nectar and protection in developing tobacco floral nectaries. American Journal of Botany, (Cover Photo) 94:12-24.

  • Carter, C, RA Healy, N O’Toole, SSM. Naqvi, G Ren, S Park, G Beattie, HT Horner, and RW. Thornburg. 2007. Tobacco nectaries constitutively express a novel NADPH oxidase that is implicated in the defense of floral reproductive tissues. Plant Physiology 143:389-399.

  • Ortiz-Peréz, E., H.T. Horner, S.J. Hanlin, and R.G. Palmer. 2006. Insect-mediated seed set evaluation of 21 soybean lines segregating for male sterility at 10 different loci. Euphytica 152:351-360.

  • Cervantes-Martinez, T, HT Horner, RG Palmer, T Hymowitz, and AHD Brown. 2006. Calcium oxalate crystal macropattern in leaves of species from groups Glycine and Shuteria (Glycininae; Phaseoleae; Papilionoideae; Fabaceae). Canadian Journal of Botany 83:1410-1421.

  • Ortiz-Perez, E, HT Horner, SJ Hanlin, and RG Palmer. 2006. Evaluation of insect-mediated seed set among soybean lines segregating for male sterility at the ms6 locus. Field Crops Research (England) (97):353-362.

  • Lersten, NR, and HT Horner. 2006. Crystal macropattern development in Prunus serotina (Rosaceae; Prunoideae) leaves. Annals of Botany 97:723-729.

  • Pepper, TM, R DenAdel, C Van Allen, and HT Horner. 2005. The Bessey Microscopy Facility: a biotechnology and life sciences center at Iowa State University. Microscopy & Microanalysis 11:894-895.

  • Healy, RA, HT Horner, TB Bailey, and RG Palmer. 2005. A microscopic study of the trichomes on gynoecia of normal and tretraploid Clark cultivars of Glycine max and seven near isogenic lines.. International Journal of Plant Sciences (Cover Photo) 16:415-425.

  • Al-Wahsh, I, HT Horner, RG Palmer, MB Reddy, and LK Massey. 2005. Oxalate and phytate of soy foods. Journal of Agricultural and Food Chemistry 53:5670-5674.

  • Lersten, NR, and HT Horner. 2005. Macropattern of styloid and druse crystals in Quillaja (Quillajaceae) bark and leaves.. International Journal of Plant Sciences (Cover Photo) 166:705-711.

  • Horner, HT, T Cervantes-Martinez, R Healy, MB Reddy, BL Deardorf, TB Bailey, I Al-Wahsh, LK Massey, and RG Palmer. 2005. Oxalate and phytate concentrations in seeds of soybean cultivars [Glycine max (L.)]. Journal of Agricultural and Food Chemistry 53:7870-7877.

  • Lersten, NR, and HT Horner. 2005. Development of the calcium oxalate crystal macropattern in pomegranate (Punica granatum, Punicaceae). American Journal of Botany (Cover Photo) 92:1935-1941.

  • Healy, RA, HT Horner, CR Bronson. 2004. Visualization of the extracellular matrix of Cochliobolus heterostrophus and a mutant strain with a modified extracellular matrix on leaf surfaces and within leaves of Zea mays. Canadian Journal of Botany 82:75-88.

  • Lersten, NR, and HT Horner. 2004. Calcium oxalate crystal macropattern development during Prunus virginiana (Rosaceae) leaf growth.. Canadian Journal of Botany 82:1800-1808.

  • Ilarslan, H, HT Horner and RG Palmer. 2003. Megagametophyte abnormalities of near isogenic female partial-sterile soybean mutants (Glycine max; Leguminosae).. Journal of Plant Research (Japan) 16:141-149.

  • Rosin, FM, JK Hart, HT Horner, PJ Davies and DJ Hannapel. 2003. Overexpression of a knotted-like homeobox gene of potato alters vegetative development by decreasing gibberellin accumulation. Plant Physiology 132:106-117.

  • Thornburg RW, C Carter, A Powell, R Mittler, L Rizhsky, HT Horner. 2003. A major function of the tobacco floral nectary is defense against microbial attack. Plant Systematics & Evolution 238:211-218.

  • Horner, HT, T Cervantes-Martinez, R Healy and RG Palmer. 2003. Floral nectary development and structure in Glycine max (Leguminosae). International Journal of Plant Sciences 164:675-690.

  • Smith, MA, RG Palmer and HT Horner. 2002. Microscopy of a cytoplasmic male-sterile soybean from an interspecific cross between Glycine max and G. soja.. American Journal of Botany 89:417-426.

  • Massey, LK, LM Grentz, HT Horner and RG Palmer. 2002. Soybean and soyfood consumption increases oxalate excretion.. Topics in Clinical Nutrition 17:49-59.

  • Feng, L, C Xiangqin, HT Horner, H Weiner, and PS Schnable. 2001. Mitochondrial aldehyde dehydrogenase activity is required for male fertility in maize (Zea mays L.). Plant Cell (Cover Photo) 12:1063-1078.

Area of Expertise: 
Cellular and developmental biology of male sterility in crop plants and plant calcium oxalate; light and electron microscopy methods
B.A., Northwestern University, 1959
M.S., Northwestern University, 1961
Ph.D., Northwestern University, 1964
0106 Molecular Biology Building