Franz J. HoffmannAssociate Professor, Developmental & Cell Biology |
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Research Interests |
Regeneration of cultured plant cells and somatic cell genetics. | |
| URL | devcell.bio.uci.edu/faculty/hoffman.html | |
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Research Abstract |
Isolated plant protoplasts, "naked" cells that have been enzymatically stripped of their walls, and microspores, an early developmental stage of the pollen, are our main tools to study the initiation and mechanism of cell division in cultures of isolated single cells. For several species or, in the case of protoplasts, tissues, these isolated cells can be induced to divide with standard techniques. However, it has been impossible to trigger consecutive divisions in many other species and tissues. The reasons for this recalcitrancy to regeneration are largely unknown, and the question of how to induce such recalcitrant isolated cells to undergo cell division is a focal point of the laboratory. The respective investigations include aspects of cell wall synthesis in isolated protoplasts which is a prerequisite for their division, microtubule transition, and cytoplasmic streaming as well as neoplastic systems, such as genetic tumors and root nodules. Upon division, cultured single cells can give rise to callus clones which are induced to regenerate plants. If microspores are used for regeneration the resulting plants may be haploid and, thus, can serve as a source of large numbers of haploid protoplasts which are easier to manipulate genetically than the more complex hi8her ploid genomes. This cycle, from plants to single cells and back to plants, can be used for clonal propagation or, if a genetic manipulation is applied to the single cell, for the production of new, genetically engineered geno-types. Techniques used to study cell regeneration have led immunofluorescence and electron microscopy of the cytoskeleton, laser microsurgery of cellular structures such as cytoplasmic strands and organelles, and modifications of cell culture procedures. Genetic manipulation techniques focus on protoplast fusion and DNA uptake into microspores. To fuse protoplasts from different, sexually noncompatible species we have led chemo-, electro-, and laser-fusion techniques. The development of an automated tissue culture procedure for the clonal propagation of potato has been investigated in cooperation with research groups in UCI's School of Engineering, the Department of Information and Computer Science, and Teohnion, Haifa, Israel, applying computer imaging and conveyor belt techniques. Joint research projects are also performed with groups in Japan and Germany. Numerous species are utilized, selected as models by experimental needs such as genomic structure or regenerability (Arabidopsis, Brachycome, Crepis, Hybiscus, Nicotiana) or for their economic importance, such as Brassica (mustard), Colocasium (taro), Fagopyrum (buckwheat), Glycine (soybean), Secale (rye), and Solanum (potato). |
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| Publications |
Hoffmann-Tsay, S.-S., R. Ernst and F. Hoffmann. 1994. Design, synthesis and application of surface-active chemicals for the promotion of electrofusion of plant protoplasts. Bioelectrochem. Bioenerg. 34: 115. |
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| Hoffmann, F. and S.-S. Hoffmann-Tsay. 1994. Growth regulator-free plant regeneration and habituated cell suspensions from carrot protoplasts. Differentiation 57: 1. | ||
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Hoffmann, F., Sibley, R.B., and Tsay, S-S. (1988). Transgenic antibiotic resistance may be differentially silenced in germinating pollen grains. Plant Cell Reports 7, 542-545. |
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Hahne, G., Hoffmann, F. (1985). Cortical microtubular lattices: Absent from mature mesophyll and necessary for cell division? Planta 166, 309-313. |
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Hoffmann, F., Adachi, T. (1981). "Arabidobrassica": Chromosomal recombination and morphogenesis in asymmetric intergeneric hybrid cells. Planta 153, 586-593 |
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| Graduate Programs |
Cell Biology Developmental Biology and Genetics |
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| Link to this profile | http://www.faculty.uci.edu/profile.cfm?faculty_id=2495 | |
| Last updated | 07/29/2005 | |