Dr. Steve Rodermel, Distinguished Professor, received his B.A. in Philosophy from Yale University, his M.S. in Zoology and Physiology from the University of Wyoming, and his Ph.D. in Cellular and Development Biology from Harvard University. After serving as a postdoctoral fellow, research associate, and lecturer at Harvard, Dr. Rodermel joined the faculty at Iowa State University in 1990 as an Assistant Professor. In 1997 he was a Visiting Professor with the Research Institute of Innovative Technology for the Earth (RITE) in Kyoto, Japan, and during 2003-2005 he served as a Program Director in the Integrative Organismal Biology Division at the National Science Foundation in Washington, D.C. At ISU, Dr. Rodermel served two years as chair of the Interdepartmental Genetics Program and three years as Associate Dean for Research in the College of Liberal Arts and Sciences. Dr. Rodermel was named a AAAS Fellow in 2011. In 2014, Dr. Rodermel was named Distinguished Professor.
The Rodermel lab is interested in defining the factors that regulate chloroplast biogenesis. During this process, photosynthetically-competent chloroplasts develop from undifferentiated proplastids in meristematic tissues, or from etioplasts following illumination of dark-grown seedlings. Variegation mutants are powerful systems to explore mechanisms of chloroplast biogenesis. The leaves of these mutants have green sectors with normal-appearing chloroplasts and white sectors with defective chloroplasts. Variegations can be produced by mutations in nuclear genes or in organelle genes (chloroplast or mitochondrial): whereas the white sectors are always associated with the mutant gene, the green sectors can have either a wild type or mutant genotype. We are interested in nuclear-gene-induced variegations in which the cells of the mutant have a uniform (mutant) genotype. This raises the question how the green cells compensate for the mutant defect. Our research has been guided by two questions:
1. What is the gene product defined by the variegation locus? Our goal here is to understand the function of the protein, how it is regulated, and what role it plays in photosynthesis and chloroplast biogenesis.
2. How do the green cells bypass the requirement for the defective gene product? This question provides insight into pathways and regulatory networks of chloroplast biogenesis in which the gene product is involved.
For a number of years we have focused on two variegations — the immutans and var2 mutants of Arabidopsis. The IMMUTANS gene product is localized in plastid membranes and is a versatile terminal oxidase (termed PTOX, for plastid terminal oxidase). It serves as a redox factor in carotenoid biosynthesis, chlororespiration, and oxidative stress avoidance. PTOX also participates in control of the redox poise of the plastoquinone pool, and can act as a photosynthetic safety valve during light stress conditions (e.g., light, cold). In this capacity, it shunts excess electrons from the PQ pool to oxygen, forming water. VAR2, on the other hand, is a subunit of the FtsH zinc metalloprotease complex on the thylakoid membrane. This complex plays a central role in protein quality control in plastids, and it mediates a number of membrane modeling events that occur during thylakoid membrane biogenesis. In chloroplasts, its most prominent role is in the PSII repair cycle, where it degrades photodamaged D1 proteins.
The Rodermel lab is interested in defining the regulatory mechanisms underlying PTOX and VAR2 function using immutans and var2 as tools. The principal method involves the generation and characterization of second-site genetic suppressors of these mutants. It is presumed that such suppressors define activities that bypass the need for PTOX and VAR2, since such suppressors give rise to all-green, photosynthetically-competent plants. To date, a number of var2 and immutans suppressor lines have been isolated, and over a dozen have been characterized at the molecular level. Many of these suppressors are components of the chloroplast translation apparatus (for var2 suppressors), or are novel thylakoid membrane proteins (for var2 and immutans suppressors). Some of these suppressors replace the activity of VAR2 or PTOX during chloroplast biogenesis. For example, it has recently been demonstrated that an activation- tagged version of the mitochondrial protein AOX2 (alternative oxidase 2) is able to rescue the immutans phenotype, suggesting that this protein is dual-targeted to both organelles, and that it normally supplements PTOX activity during chloroplast biogenesis. In addition to suppressors that replace PTOX and VAR2 activity , others act in a more indirect manner to compensate for loss of PTOX or VAR2; mechanisms of suppression in these lines are a current topic of investigation.
Selected Publications since 2000
- Miller, A., C. Schlagnhaufer, M. Spalding and S. Rodermel. 2000. Carbohydrate regulation of leaf development: prolongation of leaf senescence in Rubisco antisense mutants of tobacco. Photosynthesis Research 63: 1-8.
- Chen, M, Y.D. Choi, D.F. Voytas and S. Rodermel. 2000. Mutations in the Arabidopsis VAR2 locus cause leaf variegation due to the loss of a chloroplast FtsH protease. Plant Journal 22: 303-313. (Cover article).
- Baum, T.J., M.J.E. Wubben, K.A. Hardy, H. Su and S.R. Rodermel. 2000. A screen for Arabidopsis thaliana mutants with altered susceptibility to Heterodera schachtii. J. Nematology 32: 166-173.
- Aluru, M., H. Bae, D. Wu and S. Rodermel. 2001. The Arabidopsis immutans mutation affects plastid differentiation and the morphogenesis of white and green sectors in variegated plants. Plant Physiol. 127: 67-77.
- Rodermel, S. 2001. Pathways of plastid-to-nucleus signaling. Trends Plant Sci. 6: 471-478.
- Schoefs, B., E. Darko and S. Rodermel. 2001. Photosynthetic pigments, photosynthesis and plastid ultrastructure in RbcS antisense DNA mutants of tobacco (Nicotiana tabacum). Z. Naturforsch 56c: 1067-1074.
- Rodermel, S. 2001. Arabidopsis variegation mutants. In The Arabidopsis Book. C. Somerville and E.M. Meyerowitz, eds. (American Society of Plant Biologists, Rockville, MD) http://www.aspb.org/publications/arabidopsis/
- Rizhsky, L., E. Hallak-Herr, F. Van Breusegem, S. Rachmilevitch, J. Barr, S. Rodermel, D. Inze and R. Mittler. 2002. Double antisense plants lacking ascorbate peroxidase and catalase are less sensitive to oxidative stress than single antisense plants lacking ascorbate peroxidase or catalase. Plant Journal 32: 329-342.
- Stessman, D., A. Miller, M. Spalding and S. Rodermel. 2002. Regulation of photosynthesis during Arabidopsis leaf development in continuous light. Photosynthesis Research 72: 27-37.
- Rodermel, S. and S. Park. 2003. Pathways of intracellular communication: tetrapyrroles and plastid-to-nucleus signaling. BioEssays 25: 631-636.
- Aluru, M.R and S.R. Rodermel. 2004. Control of chloroplast redox by the IMMUTANS terminal oxidase. (Refereed review). Physiologia Plantarum 120: 4-11. (Cover Article)
- Barr, J., W.S. White, L. Chen, H. Bae and S. Rodermel. 2004. The GHOST terminal oxidase regulates developmental programming in tomato fruit. Plant, Cell & Environment 27: 840-852. (Cover article)
- Lonosky, P.M., X. Zhang, V.G. Honavar, D.L. Dobbs, A. Fu and S.R. Rodermel. 2004. A proteomic analysis of maize chloroplast biogenesis. Plant Physiology 134: 560-574.
- Yu, F., S. Park and S.R. Rodermel. 2004. The Arabidopsis FtsH metalloprotease gene family: interchangeability of subunits in chloroplast oligomeric complexes. Plant Journal 37: 864-876.
- Stessman, D., M. Spalding and S. Rodermel. 2004. Short-term and long-term regulation of photosynthesis during leaf development. In Handbook of Photosynthesis. M. Pessarakli, ed. (Marcel Dekker, Inc., New York), pp. 441-449.
- Park, S., and S.R. Rodermel. 2004. Mutations in ClpC2/Hsp100 suppress the requirement for FtsH in thylakoid membrane biogenesis. Proc. Natl. Acad. Sci. USA 101: 12765-12770.
- Rodermel, S., J.-F. Viret and E. Krebbers. 2005. Lawrence Bogorad (1921-2003), a pioneer in photosynthesis research: a tribute. Photosynthesis Research 83: 17-24. (Invited tribute)
- Baerr, J.N., J.D. Thomas, B.G. Taylor, S.R. Rodermel and G.R. Gray. 2005. Differential photosynthetic compensatory mechanisms exist in the immutans mutant of Arabidopsis thaliana. Physiologia Plantarum 124: 390-402. (Cover Article).
- Yu, F., S. Park and S.R. Rodermel. 2005. Functional redundancy of AtFtsH metalloproteases in thylakoid membrane complexes. Plant Physiol. 138: 1957-1966.
- Alsheikh, M., and S. Rodermel. 2005. Genetics and genomics of chloroplast biogenesis. Maydica 50: 443-449. (Invited review: 50th anniversary of Maydica).
- Fu, A., S. Park and S. Rodermel. 2005. Sequences required for the activity of PTOX (IMMUTANS), a plastid terminal oxidase: in vitro and in planta mutagenesis of iron-binding sites and a conserved sequence that corresponds to Exon 8. J. Biol. Chem. 280: 42489-42496. (Cover Article).
- Aluru, M.R., F. Yu, A. Fu and S. Rodermel. 2006. Arabidopsis variegation mutants: new insights into chloroplast biogenesis. J. Experimental Botany 57: 1871-1881. (Refereed review).
- Rosso, D., A.G. Ivanov, A. Fu, J. Geisler-Lee, L. Hendrickson, M. Geisler, G. Stewart, M. Krol, V. Hurry, S.R. Rodermel, D.P. Maxwell and N.P.A. Hüner. 2006. IMMUTANS does not act as a stress-induced safety valve in the protection of the photosynthetic apparatus of Arabidopsis during steady state photosynthesis. Plant Physiol. 142: 574-585.
- Aluru, M.R., D.J. Stessman, M.H. Spalding and S.R. Rodermel. 2007. Alterations in photosynthesis in Arabidopsis lacking IMMUTANS, a chloroplast terminal oxidase. Photosynthesis Research 91: 11-23.
- Yu, F., A. Fu, M. Aluru, S. Park, Y. Xu, H. Liu, X. Liu, A. Foudree, M. Nambogga and S. Rodermel. 2007. Variegation mutants and mechanisms of chloroplast biogenesis. Plant Cell & Environment 30: 350-365. (Refereed review) (Cover Article).
- Varbanova, M., S. Yamaguchi, Y. Yang, K. McKelvey, A. Hanada, R. Borochov, F. Yu, Y. Jikumaru, J. Ross, D. Cortes, C.-J. Ma, J. P. Noel, L. Mander, V. Shulaev, Y. Kamiya, S. Rodermel, D. Weiss and E. Pichersky. 2007. Methylation of gibberellins by Arabidopsis GAMT1 and GAMT2. Plant Cell 19: 32-45.
- Taber, H. G., P. Perkins-Veazie, S. Li, W. White, S. Rodermel and Y. Xu. 2008. Enhancement of tomato fruit lycopene by potassium is cultivar dependent. HortScience 43: 159-165.
- Yu, F., X. Liu, M. Alsheikh, S. Park and S. Rodermel. 2008. Mutations in SUPPRESSOR OF VARIEGATION1, a factor required for normal chloroplast translation, suppress var2-mediated leaf variegation in Arabidopsis. Plant Cell 20: 1786-1804.
- Aluru, M., Y. Xu, R. Guo, Z. Wang, S. Li, W. White, K. Wang and S. Rodermel. 2008. Generation of transgenic maize with enhanced provitamin A content. J. Experimental Botany 59: 3551-3562.
- Rodermel. S. 2008. Don’t Overlook Valencia: the ISU Summer Study Abroad Program for Biology. Des Moines Register, Sunday Travel Section (Dec 7, 2008).
- Aluru, M.R., J. Zola, A. Foudree and S.R. Rodermel. 2009. Chloroplast photooxidation-induced transcriptome reprogramming in Arabidopsis immutans white leaf sectors. Plant Physiol. 150: 904-923.
- Fu, A., M. Aluru and S.R. Rodermel. 2009. Conserved active site sequences in Arabidopsis plastid terminal oxidase (PTOX): in vitro and in planta mutagenesis studies. J. Biol. Chem. 284: 22625-22632.
- Rosso, D., R. Bode, W Li, M. Krol, D. Saccon, S. Wang, L.A. Schillaci, S.R. Rodermel, D.P. Maxwell, and Norman P.A. Hüner. 2009. Photosynthetic redox imbalance governs leaf sectoring in the Arabidopsis thaliana variegation mutants immutans, spotty, var1, and var2. Plant Cell 21: 3473–3492. (Cover Article).
- Liu, X, F. Yu and S. Rodermel. 2010. Arabidopsis chloroplast FtsH, var2 and suppressors of var2 leaf variegation: a review. (Refereed, invited “expert” review) J. Integrative Plant Biology 52: 750-761.
- Liu, X, S. Rodermel and F. Yu. 2010. A var2 leaf variegation suppressor locus, SUPPRESSOR OF VARIEGATION3, encodes a putative chloroplast translation elongation factor that is important for chloroplast development in the cold. BMC Plant Biology 10: 287-305.
- Foudree, A., M. Aluru and S. Rodermel. 2010. PDS activity acts as a rheostat of retrograde signaling during early chloroplast biogenesis. Plant Signaling Behavior 5: 1619-1622.
- Liu, X, F. Yu and S. Rodermel. 2010. An Arabidopsis pentatricopeptide repeat protein, SUPPRESSOR OF VARIEGATION7, is required for FtsH-mediated chloroplast biogenesis. Plant Physiol. 154: 1588-1601.
- Yu, F., S.-S. Park, X. Liu, A. Foudree, A. Fu, M. Powikrowska, A. Khrouchtchova, P.E. Jensen, J.N. Kriger, G.R. Gray and S.R. Rodermel. 2011. SUPPRESSOR OF VARIEGATION4, a new var2 suppressor locus, encodes a pioneer protein that is required for chloroplast biogenesis. Molecular Plant 2: 229-240.
- Yu, X., L. Li, J. Zola, M. Aluru, H. Ye, A. Foudree, H. Guo, S. Anderson, S. Aluru, P. Liu, S. Rodermel and Y. Yin. 2011. A brassinosteroid transcriptional network revealed by genome-wide identification of BES1 target genes in Arabidopsis thaliana. Plant Journal. 65: 634-646.
- McDonald, A.E., A.G. Ivanov, R. Bode, D.P. Maxwell, S.R. Rodermel, N.P.A. Hüner. 2011. Flexibility in photosynthetic electron transport: the physiological role of plastoquinol terminal oxidase (PTOX). (Refereed review) Biochim. Biophys. Acta. 1807: 954–967.
- Aluru, M., S. Rodermel, and M. Reddy. 2011. Genetic modification of low phytic acid 1-1 maize to enhance iron content and bioavailability. Journal of Agricultural and Food Chemistry 59: 12954-12962.
- Wang, M., X. Liu, R. Wang, W. Li, S. Rodermel and F. Yu. 2012. Overexpression of a putative Arabidopsis BAHD acyltransferase causes dwarfism that can be rescued by brassinosteroid. Journal of Experimental Botany 63: 5787–5801.
- Foudree, A., A. Putarjunan, S. Kambakam, T. Nolan, J. Fussell, G. Pogorelko and S. Rodermel. 2012. The mechanism of variegation in immutans provides insight into chloroplast biogenesis. Peer-reviewed Review. Frontiers in Plant Physiology 3: Article 260 (doi: 10.3389/fpls.2012.00260)
- Fu, A. H. Liu, F. Yu, S. Kambakam, S. Luan and S. Rodermel. 2012. Alternative oxidases (AOX1a and AOX2) can functionally substitute for plastid terminal oxidase in Arabidopsis chloroplasts. Plant Cell 24: 1579-1595.