Liberty Hyde Bailey Professor of Plant Molecular Biology
Publications | Research | Faculty
Background:
Maureen R. Hanson is Liberty Hyde Bailey Professor in the Department of Molecular Biology & Genetics. She received a B.S. degree in botany at Duke University and a Ph.D. in cell and developmental biology from Harvard University. After completing an NIH postdoctoral fellowship at Harvard, she joined the faculty of the biology department at University of Virginia. In 1985 she moved to Cornell, where she became the first coordinator of the Program in Plant Cell and Molecular Biology. She is presently a member of the graduate Fields of Genetics and Development, Plant Biology, and Biochemistry, Molecular, and Cell Biology, a joint member of the Department of Plant Biology, and Director of the Plant Cell Culture and Transformation Facility.
Courses Taught:
- BioGD 482 Sec. 05. Molecular Biology of Plant Organelles (Spring)
- BioPL 482 Sec. 05. Plant Biology (Spring)
- BioBM 641. (also BioPL 641)Laboratory in Plant Molecular Biology (Fall)
- BioPL 741. Problems in Plant Molecular Biology (Spring)
- BioPL 742. Current Topics in Plant Molecular Biology (Fall)
- BioGD 781. Problems in Genetics and Development (Fall)
Links:
- RNA editing in organelles
- Functional genomics of chloroplast RNA binding proteins
- Dynamic organization of the plant cell
- Expression of foreign proteins in chloroplast
- Mitochondria during reproductive development
RNA editing in chloroplasts and mitochondria
In the process of RNA editing, RNA nucleotides are inserted, deleted, or modified, resulting in a difference between the actual RNA and the RNA predicted from genomic DNA. RNA editing is known to occur in a variety of organsims, including mammals, insects, plants and microorganisms. In plants, RNA editing occurs in RNAs encoded by the orgaenelle genomes located in chloroplasts and mitochondria. During RNA editing in plants, cytidines encoded by genomic DNAs are modified to uridine in transcripts.
We are using genetic and biochemical techniques to examine editing in mitochondria and chloroplasts. It is possible to transform chloroplast genomes with chimeric genes to probe the features of transcripts that are important in RNA editing. We wish to understand RNA editing at the molecular level, including how cytidines are selected for editing and what macromolecules are involved in the editing process.
Functional genomics of chloroplast RNA-binding proteins in maize and rice
RNA metabolism in chloroplasts, which is critical for photosynthesis and plant development, is controlled by RNA-binding proteins expressed from nuclear genes and imported into the organelles. A large number of genes encoding proteins carrying possible RNA-binding motifs can be identified in genomic databases such as PlantRBP.
We are collaborating with Prof. Alice Barkan (U. Oregon) to identify the function of maize chloroplast RNA-binding proteins by exploiting her Photosynthesis Mutant Library for isolation of mutants containing Mu insertions in genes predicted to encoding chloroplast RNA-binding proteins. Effects of mutations on processes such as chloroplast RNA splicing, 5’ and 3’ processing, editing, and stability are being evaluated. Identification of RNA targets of RNA-binding proteins will be performed using an approach involving immunoprecipitation and microarray technology.
Probing plant cell organization with organelle-targeted fluorescent proteins
The ability to label different subcellular locations with the green fluorescent protein (GFP) has made it possible to visualize intracellular activities in living cells. We have introduced chimeric genes which express GFP in a variety of organelles within the plant cell in order to study the dynamics of cell organization. Labeling plastids with GFP led to the rediscovery of tubules emanating from plastids. Now termed stromules for stroma-filled tubules, the function of these unexpected structures remains a topic for study.
A web essay on stromules, authored by Hanson and Köhler, can be seen at: http://www.plantphys.net/article.php?ch=e&id=122
Stromules are particularly abundant in non-green plant cells such as cells in tissue culture.
A cultured cell expressing nuclear-encoded, chloroplast-targeted green fluorescent protein was imaged with an Olympus FluoView 1000 confocal microscope. Stromules sometimes connect two plastid bodies.
Expression of foreign proteins in chloroplasts
Because there are multiple copies of the chloroplast genome within each organelle and leaf cells each typically contain 100-200 chloroplasts, in one leaf cell, there can be thousands of copies of a transgene inserted into the chloroplast genome. Such an elevated copy number offers the possibility to create chloroplast transgenic plants that express foreign proteins as high as 30-40% of total soluble leaf protein. However, some foreign proteins are expressed only at low levels in transgenic chloroplasts. Factors that can affect foreign protein yield include the gene expression signals incorporated into the transgene, the stability of the foreign protein, and environmental growth conditions. In collaboration with Prof. Beth Ahner’s laboratory (Biological and Environmental Engineering, Cornell), we are determining how to optimize production of cellulolytic enzymes from the bacterium Thermobifida fusca in chloroplast transgenic plants. Plants expressing cellulases at high levels could be harvested to obtain enzymes for glucose production from biomass.
Chloroplast transgenic plant expressing T. fusca Cel6A
The role of mitochondria and mitochondrial gene expression in developmental processes in plants.
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| Normal petunia with abundant pollen | Flower from CMS petunia: |
Mutations in mitochondrial genomes are known to create novel genes whose expression disrupts pollen development. Plants carrying such mutations are termed cytoplasmic male sterile or CMS. Individuals of many plant species, including maize, rice, sunflower, petunia, cauliflower, and cabbage, exhibit CMS. Breeding lines have been developed that utilize CMS in order to create hybrid seedany progeny of a male sterile plant must arise from cross-pollination.
We have cloned a mitochondrial gene which encodes CMS in petunia and are attempting to understand its mechanism of action. The gene encodes an abnormal protein which disrupts mitochondrial activities.
A nuclear gene (the Rf gene) is known to interact with this mutant mitochondrial gene, reducing its expression and thereby restoring normal fertility to plant genotypes. We have identified the petunia restorer gene by cloning candidate genes from map position and demonstrating that one such gene is able to confer fertility on CMS petunia lines. We are presently attempting to understand to learn how the restorer gene, a member of the large pentatricopeptide repeat (PPR) gene family, prevents the expression of an abnormal mitochondrial gene.
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| Normal mitochondrion | Mitochondrion in CMS petunia contains abnormal gene and protein | Mitochondrion in Rf petunia lacks abnormal protein though contains the abnormal mitochondrial gene |
Supplementary information to journal articles
Additional images and time-laspse movies can be seen at More information for journal articles
Kohler, R.H. and M.R. Hanson. 2000. Plastid tubules of higher plants are tissue-specific and developmentally regulated J. Cell Science 113: 81-89. Köhler, R.H. 1998.
FP for in vivo imaging of subcellular structures in plant cells. Trends in Plant Science 3 :317-320. Hanson, M.R. and R.H. Köhler, 2001.
GFP imaging: methodology and application to investigate cellular compartmentation in plants. J. Exp. Botany 52: 529-539.
Kwok, E.Y. and M.R. Hanson. 2004. Stromules and the dynamic nature of plastid morphology. J. Microscopy, 214:124-137.
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Click here to view Dr. Hanson's PubMed listings.
Hanson, M.R. and A. Sattarzadeh. 2008. Dynamic morphology of plastids and stromules in angiosperm plants. Plant Cell and Environment, in press (available as epub).
Bentolila, S., L.E. Elliott, and Maureen R. Hanson. 2008. Genetic architecture of mitochondrial editing in Arabidopsis. Genetics 178:1693-708
Heller, W.P., M.L. Hayes, and M.R. Hanson. 2008. Cross-competition in editing of chloroplast RNA in vitro implicates sharing of trans-factors between different C targets. J. Biol. Chem., 283: 7314-7319. (“Paper of the Week”)
Yu L.X., B.N. Gray, C.J. Rutzke, L.P. Walker, D.B. Wilson, M.R. Hanson. 2007. Expression of thermostable microbial cellulases in the chloroplasts of nicotine-free tobacco. J. Biotechnol. 131:362-369
Reisen, D. and M.R. Hanson. 2007 Association of six YFP-myosin XI-tail fusions with mobile plant cell organelles BMC Plant Biology 7:6. http://www.biomedcentral.com/1471-2229/7/6
Hayes, M.L. and M.R. Hanson. 2007. Assay of editing of exogenous RNAs in chloroplast extracts of Arabidopsis, maize, pea, and tobacco. Meth. Enzymol. 424:459-82.
Holzinger, A, O. Buchner, C. Lutz, M.R. Hanson 2007. Temperature-sensitive formation of chloroplast protrusions and stromules in mesophyll cells of Arabidopsis thaliana. Protoplasma 230:23-30.
Gillman, J.D., S. Bentolila, and M.R. Hanson 2007. The Petunia Restorer of Fertility protein is part of a large mitochondrial complex that interacts with transcripts of the CMS-associated locus. Plant Journal 49:217-27 http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-313X.2006.02953.x
Hayes, M.L. and M.R. Hanson. 2007. Identification of a sequence motif critical for editing of a tobacco chloroplast transcript. RNA 13:281-8 http://www.rnajournal.org/cgi/content/full/13/2/281
Hayes, M.L., M.L. Reed, C.E. Hegeman, and M.R. Hanson 2006. Sequence elements critical for efficient RNA editing of a tobacco chloroplast transcript in vivo and in vitro. Nuc. Acids Res. 34:3750-62. http://nar.oxfordjournals.org/cgi/content/full/34/13/3742
Xu, Y., H. Ishida, D. Reisen, and M. R Hanson. 2006. Upregulation of a tonoplast-localized cytochrome P450 during petal senescence in Petunia inflata. BMC Plant Biol. 6:8. http://www.biomedcentral.com/1471-2229/6/8