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Regulation of Gene Expression during Plant Embryogenesis
Department of Plant and Soil Sciences
Somatic embryogenesis is a poorly understood process that is of value to agriculture because a means of regeneration, either by organogenesis or somatic embryogenesis, is necessary for genetic engineering for crop improvement of most plants. AGL15 is a protein that controls expression of genes, is most abundant during embryo development, and can promote somatic embryogenesis. The proposed work to identify genes directly and indirectly controlled by AGL15 will contribute to a better understanding of genetic processes controlling zygotic and somatic embryo development.
2011 Project Description
Two postdoctoral scholars have received training in the past year supported by funds from the National Science Foundation (started 2009) and the United Soybean Board (started 2010). Both postdocs presented their findings at the 22nd International Conference on Arabidopsis Research held in Madison, Wisconsin in 2011 and both will be preparing manuscripts on their work in the upcoming year.
The project has also led to ongoing collaborations. In 2011 the book Molecular Biology volume 754: Plant Transcription Factors: Methods and Protocols, Humana Press (J.M. Walker, Series Editor), co-edited by Ling Yuan and myself was published.
Also in 2011, a workshop for 5th grade students was run as a collaboration with Raven Run Nature Sanctuary to teach students about using the scientific method to investigate environmental control of flowering time.
We are continuing to use combinations of mutants, hormones and inhibitors of hormones to tease apart cross-talk between gene products and hormones in somatic embryogenesis. In the past year, we have made some interesting observations and will be preparing a manuscript in the coming year.
The hope is that work in the model plant Arabidopsis will contribute to an understanding of embryogenesis that can be applied to crop plants to facilitate recovery of transgenic plants by somatic embryo development. In fact we have been performing work to test whether stable introduction of a soybean ortholog of a gene involved in embryogenesis in Arabidopsis will also promote somatic embryo formation in Glycine max and results look encouraging. This should allow extension of competency for regeneration by somatic embryogenesis to genotypes recalcitrant for the process.
As part of this, in the past year we have used microarrays to measure transcript abundance in response to AGL15 (a transcriptional regulator expressed during embryogenesis) accumulation in soybean. We are able to compare these results to results already obtained in Arabidopsis. Furthermore, we have optimized a modification of the chromatin immunoprecipitation (ChIP) procedure to isolate DNA fragments directly bound by AGL15 in soybean and will be able to distinguish direct from indirect targets to understand the regulatory networks in which AGL15 is involved and that may promote embryo development.
We have previously performed ChIP analysis in Arabidopsis and so can compare results between these two species. We continue to analyze downstream targets of AGL15 and are extending what we've learned about the regulatory network to other embryo-expressed factors. In the past year, we have optimized ChIP for one such regulator and will proceed with whole genome analysis early this year and we have developed materials and tools for another regulator. Our hope is to contribute to a basic understanding of gene regulation controlling embryogenesis in order to develop strategies to optimize 1.) seed development and 2.) regeneration by somatic embryogenesis.
Yumei Zheng and Sharyn E. Perry. (2011) Chapter 16: Chromatin immunoprecipitation to verify or to identify in vivo protein-DNA interactions. In: Methods in Molecular Biology: Plant Transcription Factors: Methods and Protocols, volume 754. Edited by Ling Yuan and Sharyn E. Perry. Springer Science and Business Media, LCC; Humana Press. Pages 277-291.