ASU SoLS Faculty: Robert W. Roberson

Dr. Roberson joined ASU in 1989. He is also the Director of the Life Sciences Electron Microscope Facility. He received a Ph.D. from the Department of Plant Biology at the University of Georgia.

My research examines aspects of cell growth and development in fungi. How fungal cells attain their characteristic morphology has long been of interest to mycologists and cell biologists. Fungal cells typically grow by means of tubular shaped hyphae that elongate at their tips. The process of apical growth and cellular morphogenesis in fungi can be viewed as a highly polarized system of exocytosis involving the net migration of cytoplasmic vesicles carrying cell surface precursors and enzymes needed for plasma membrane and wall formation to actively growing regions of the cell. There appears to be two distinct types of vesicular movement: 1) movement over "long" distances where vesicles are transported from areas of synthesis (i.e., Golgi bodies) to regions of active growth and 2) movement over "short" distances where the actual fusion of vesicles with the plasma membrane is controlled. Thus, apical growth and cellular morphogenesis in fungi is regulated by the efficient and precise delivery of cytoplasmic vesicles to sites of active growth.

How fungal cells regulate and coordinate the movement of these vesicles and their ultimate fusion with the plasma membrane is not clear. Much attention in my lab is devoted to addressing these questions by examining the detailed cytology of fungal cells during periods of growth and morphogenesis where we use the model organism Aspergillus nidulans and Neurospora crassa. Cytological studies are performed both at the light and electron microscope levels. Advanced light microscope methods (e.g., laser scanning confocal, computer enhancement) are used extensively to study the organization and/or behavior of cytoplasmic components in live and fixed cells. For ultrastructural analysis, cryotechniques (e.g., propane quenching, high-pressure freezing, freeze-substitution) are used to prepare fungal specimens for transmission electron microscope (TEM) analysis. Here we use standard TEM methods as well as immunocytochemistry approaches. Furthermore, we utilize the methods available for three-dimensional analysis including serial section reconstruciton analysis and electron tompography. Results from these detailed cytological studies coupled with use of selected mutaion analysis are helping us better understand the cell biology of apical growth and morphological events in fungi.

In collaborations with Dr. Wim Vermaas (ASU), we are also very much involved with using the above-mentioned visualization and analysis methods (with the addition of high-resolution cryo-field emission scanning electron microscopy) in studies of cytoplasmic order and behavior of the model cyanobacterium Synechocystis sp. PCC 6803. Coupled with strong molecular and genetic approaches (Synechocystis was the first photosynthetic organism with its genone sequenced), Synechocystis is ideal organism for detailed structural studies to elucidate the biogenesis and organizaton of thylakoid membranes, cell wall architecture and compositional function, and cytoskeletal function. The information gained not only is valuable for understanding the physiology of cyanobacteria, but also for that of other organisms such as plants.

Selected Publications

Hohmann-Marriott, M.F., Uchida, M., van de Meene, A.M.L., Garret, M., Hjelm, B.E., Kokoori, S., Roberson, R.W. 2006. Electron tomography and its application to revealing fungal ultrastructure: Tansley Review. New Phytologist. 172:208-220.

Mouriño-Pérez, R.R., Roberson, R.W ., Bartnicki-García, S. 2006. Microtubule dynamics and organization during hyphal branching in Neurospora crassa . Fungal Genetics and Biology 43:389-400.

van de Meen A., Hohmann-Marriott M.F., Vermaas W.F.J., Roberson R.W. 2006. The three-dimensional structure of the cyanobacterium Synechocystis sp. PCC 6803. Archives of Microbiology 184:259-270.

Hohmann-Marriott, M.F., Sharp, W.P., Blankenship, R.E., Roberson, R.W. 2005. Digital position determination system for electron microscopy. Microscopy Techniques and Methods. 67:106-111.

Mohamed, H.E., Van de Meene, A.M.L., Roberson, R.W., Vermaas, W. 2005. Myxoxanthophyll is required for normal cell wall structure and thylakoid organization in the cyanobacterium Synechocystis sp. strain PCC 6803. Journal of Bacteriology 187:6883-6892.

Hohmann-Marriott, M.F. Blankenship, R.E., Roberson, R.W . 2005. The ultrastructural of Chlorobium tepitum chlorosomes revealed by electron microscopy. Photosynthesis Research 86:145-154.

Uchida, M. , Roberson, R.W. , Chun, S., Kim, D. 2005. In vivo effects of the fungicide ethaboxam on microtubule integrity in Phytophthora infestans . Pest Manag Sci. 61:787-792.

Harris , S.D. , Read, N.D., Roberson, R.W ., Shaw, B., Seiler, S., Plamann, M., Momany, M. 2004.

Spitzenkörper meets polarisome: microscopy, genetics, and genomics converge. Eukaryotic Cell 4:225-229.

Lowry, D.L., Fisher, K.F., Roberson, R.W. 2004. Functional necessity of the cytoskeleton during cleavage membrane development and zoosporogenesis in Allomyces macrogynus . Mycologia 96:211-218.

Riquelme M., McDaniel, D.P., Bartnicki-García S., Roberson R.W. 2002. The effect of ropy-1 mutation on cytoplasmic organization in mature hyphae of Neurospora crassa . Fungal Genetics and Biology 37:171-179.

Woyke T., Winkelmann G., Roberson R.W. Pettit, G.R., Pettit R.K. 2002. Three-dimensional visualization of microtubules during the Cryptococcus neoformans cell cycle and effects of auristatin PHE. Antimicrobial Agents and Chemotherapy 46:3802-3808.

Pettit R.K., Hamel E., Verdier-Pinard P., Roberson R.W . , Hazen K.C., Pettit G.R., Crews L.C. 2002.

Antifungal and cancer cell growth inhibitory activities of 1-(3 ¢ ,4 ¢ ,5 ¢ -trimethoxyphenyl)-2-nitroethylene. Mycosis 45:65-74.

McDaniel, D.P., Roberson, R.W . 2000. Intracellular motility and mechanisms of control during hyphal tip growth in Allomyces . Fungal Genetics and Biology 31:223-234.

Fisher, K.E., Lowry, D.S. Roberson, R.W . 2000. Cytoplasmic cleavage in zoosporangia of Allomyces macrogynus . Journal of Microscopy 198:260-270.

Gorur, R.S., Roberson, R.W ., Burnham,J., and Hill, R. 1999. Mold growth on nonceramic insulators and

its impact on electrical performance. IEEE Power Engineering Society 23 : 345-349.

Harding, M.W., Stutz, J.C., Roberson, R.W . 1999. Host-parasite relationships in bean cultivars of varying susceptibility to bean rust. Canadian Journal of Botany 77:1551-1559.

Park, Y., Eggink, L.L., Roberson, R.W. , Hoober, K. 1999. Transfer of proteins from the chloroplast to vacuoles in Chlamydomonas reinhardtii: a pathway for degradation. Journal of Phycology. 35:528-538.

Lowry, D.S., Fisher, K.E., Roberson, R.W. 1998. Establishment and maintenance of nuclear position during zoospore formation in Allomyces macrogynus : roles of the cytoskeleton. Fungal Genetics and Biology 24:34-44.

McDaniel D.P, Roberson, R.W. 1998. ?-Tubulin is a component of the Spitzenkörper and centrosomes in hyphal tip cells of Allomyces macrogynus . Protoplasma 203:118-123.

Roberson, R.W. , Tucker, B., Pettit, G.R. 1998. Microtubule depolymerization in Uromyces appendiculatus by three new antineoplastic drugs: combretastatin A-4, dolastatin 10 and halichondrin B. Mycological Research 102:378-382 .

McNally, H.A., Kozicki, M.N., Roberson, R.W. , Whidden, T.K. 1997. Electrical Characterization of Uromyces germ tubes grown on integrated circuit substrates. Journal of Vacuum Science andTechnology. 15:779-783.

Lowry, D., Roberson, R.W. 1997. The microtubule cytoskeleton during zoospore formation in Allomyces macrogynus . Protoplasma 196:45-54.

Srijayanthi, S., Vargas, M., Roberson, R.W. 1996. Functional, organizational, and biochemical analysis of actin in the hyphal tip cells of Allomyces macrogynus . Mycologia 88:57-80.

Kozicki, M.N., Roberson, R.W. , Whidden, T.K., Kersey, S.E. 1995 Directed growth of Uromyces hyphae on integrated circuit substrates. The Journal of Vacuum Science and Technology 13:1808-1813.

Roberson, R.W. , Vargas, M. 1994. The tubulin cytoskeleton and its sights of nucleation in Allomyces macrogynus . Protoplasma 182:19-31.

Preisig, H.R., Anderson , O.R., Corliss, J.O., Moestrup, O., Powell, M.J., Roberson R.W. , Wetherbee, R. 1994. Terminology of protist cell surface structures. Protoplasma 181:1-28.

Vargas, M., Aronson, J.M., Roberson R.W. 1993. Cytological organization of hyphal tip cells of Allomyces macrogynus . Protoplasma 176:43-52.

Roberson, R.W. 1993. Cryofixation and freeze substitution of teliospores of Gymnosporangium clavipes : an ultrastructural investigation. Mycological Research 97:195-204.

Martin , C.A. , Ruter J.M., Roberson R.W. , Sharp W.P. 1993. Elemental absorption and hydration potential of polyacrylamide gels. Commun. Soil Sci. Plant Anal. 24:539-548.

Roberson, R.W. 1992. The actin cytoskeleton in hyphal cells of Sclerotium rolfsii . Mycologia 84 41-51.

Roberson, R.W. , Luttrell E.S., Fuller M.S. 1990. Mycoparasitisum of teliospores of the smut fungus Ustilago bullata by an oomycete. Canadian Journal of Botany . 68:2415-2421.

Fuller, M.S., Roberson, R.W. , Gisi, U. 1990. Effects of the sterol biosynthesis inhibitor cyproconazole on hyphal tip cells of Sclerotium rolfsii . III A cytochemical study. Pesticide Biochemistry and Physiology 36:115-126.

Roberson, R.W. , Fuller, M.S. 1990. Effects of the sterol biosynthesis inhibitor cyproconazole on hyphal tip cells of Sclerotium rolfsii. II An electron microscopic study. Experimental Mycology 14:124-135

Roberson, R.W. , Fuller, M.S., Grebski, C. 1989. Effects of the sterol biosynthesis inhibitor cyproconazole on hyphal tip cells of Sclerotium rolfsii . I A light microscopic study. Pesticide Biochemistry and Physiology 34:130-142.

Roberson, R.W. , Luttrell, E.S. 1989. Dolipore septa in Tilletia . Mycologia 81:650-652.

Sewall, T.C., Roberson, R.W. , Pommerville, J.C. 1989. Identification and characterization of Golgi equivalents from Allomyces macrogynus . Experimental Mycology 13:239-252.

Roberson, R.W. , Fuller, M.S. 1988. Ultrastructural aspects of the hyphal tip of Sclerotium rolfsii preserved by freeze substitution. Protoplasma 146:143-149.

Fuller, M.S., Roberson, R.W. 1988. The effects of sterol biosynthesis inhibitors on cleavage in Allomyces macrogynus . Mycologia 80:716-724.

Mims, C.W., Roberson, R.W. , Richardson , E.A. 1988. Ultrastructure of freeze-substituted and chemically fixed basidiospores of Gymnosporangium juniperi - virginianae . Mycologia 80:356-364.

Mims, C.W., Richardson , E.A., Roberson, R.W. 1987. Ultrastructure of basidium and basidiospore development in three species of the fungus Exobasidium . Canadian Journal of Botany 65:1236-1244.

Roberson, R.W. , Luttrell, E.S. 1987. Ultrastructure of teliospore ontogeny in Tilletia indica . Mycologia 79:753-763.

Elijah, R.D., Cheeks, K., Bohn, G., Roberson, R.W. , Green, K. 1985. Pharmacological modification of corneal endothelia intracellular Ph, intracellular potential, and corneal thickness. Current Eye Research 1:343-352.

Mims, C.W., Roberson, R.W. 1983. Ultrastructure of ornamentation development on aeciospores of Cronartium quercuum forma specialis fusiforme . Mycologia 7:400-411.

Mims, C.W., Roberson, R.W. 1981. TEM and SEM of teliospore germination and basidiospore formation in two species of the rust fungus Gymnosporangium : an overview. Texas Society for Electron Microscopy Journal 7:7-15.

PUBLICATIONS IN EDITED BOOKS

Hohmann-Marriott, M., van de Meene, A. Roberson, R.W . 2006. Electron tomography: Advances in Photosynthesis. Biophysical techniques in photosynthesis (Volume II), Series Editor Govindjee, J. Matysik and T. J. Aartsma (in press), Kluwer Academic Publishers.

Roberson, R.W. , Chandler , D.E. 1998. Rapid freezing and deep etching of cells and molecules. In : Cell Biology: A Laboratory Handbook. Eds . D. Spector, R. Goldman, and L. Leinwand. Cold Spring Harbor Laboratory Press, Cold Spring Harbor , New York . (pp.129.1-129.23).

Roberson, R.W. 1991. The hyphal tip cell of Sclerotium rolfsii : cytological observations. In : Fungal Cell Wall and Immune Response. Pp. 27-37. Eds. J.P. Latge and D. Boucias. NATO Scientific Series, Springer-Verlag , Berlin , Heidelberg .

Howard, W., Roberson, R.W. 1987. Pythium : sexual reproduction. Pp 92-93. In : Zoosporic Fungi in Teaching and Research. Eds . M.S. Fuller and A. Jaworski. Southeastern Publishing Corp.

Roberson, R.W. , Howard, W. 1987. Pythium : asexual reproduction. Pp 90-91. In : Zoosporic Fungi in Teaching and Research. Eds . M.S. Fuller and A. Jaworski. Southeastern Publishing Corp.

Roberson R.W. and D.E. Chandler. 2007. Methods in Bioimaging. Jones and Bartlett , Boston , MA . (in press).