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Environmental and Genetic Determinants of Seed Quality and Performance (From W1168)
A.B. Downie, R.L. Geneve, S.E. Perry, C.C. Baskin
Department of Horticulture
Seeds are the primary entities for propagation of food, feed, fiber, bio-fuel, and ornamental plants. America produces copious quantities of seed to grow a vast array of plants whose natural and agro-ecological niches are exceptionally diverse and in environmental conditions that are not always favorable for their germination, emergence, establishment, and persistence.
The underlying principles that influence successful plant propagation are biologically based, as are the solutions to overcoming problems that limit establishment of desirable species. Whether at the level of the individual seed, variety, field, habitat, or ecosystem, the needs for seed biology research transcend individual geographic regions.
This multistate project has had, and will continue to have, an important role in capitalizing on research opportunities that will successfully address various biological processes that enhance seed performance. Many productive research collaborations have been initiated through this multistate project, and the wide array of seed biology expertise among W-1168 participants synergistically stimulates new approaches leading to relevant new biological insights. The outcomes from these collaborations foster technical innovations applicable to the wide range of crops and natural species.
2010 Project Description
Our overall goal is to understand the ecology, biogeography and evolution of seed dormancy and germination. A concentrated effort to examine the seed dormancy mechanism of species present in biogeographical regions identified as underrepresented in the 1998 book
Seeds: Ecology, biogeography, and evolution of dormancy and germination. has resulted in publications on several species from the USA as well as species from other countries including Taiwan, Japan, China, Australia (Dodonaea), and Europe (forest herbs). Web page for the W-2168 was set up that links to all member's labs (http://www.seedresearchers.com). The Perry lab has continued to probe mechanisms underpinning plant embryogenesis by identifying genes directly and indirectly regulated by the DNA-binding MADS-factor AGL15. AGL15 accumulation correlates with competence for somatic embryogenesis.
Understanding somatic embryo development is fascinating from the basic viewpoint of determining how a cell can dedifferentiate and redifferentiate in embryo mode, as well as having practical aspects to promote regeneration of value-added transgenic plants by somatic embryogenesis. One route to contribute to determination of mechanisms of somatic embryo development is to determine genes controlled by transcriptional regulators that promote this process, such as AGL15.
We have globally mapped where AGL15 associates with DNA in vivo, resulting in ~2000 binding sites. We have combined this information with expression microarray data to determine perturbations in the transcriptome in response to increased or decreased AGL15. This has allowed us to identify genes that are likely to be directly expressed in response to AGL15 as well as genes directly repressed by AGL15, resulting in ~200 genes with a direct, consistent and significant response to AGL15.
Interestingly, other transcriptional regulators are overrepresented in the directly expressed list, but not the directly repressed list. DNA motifs that AGL15 recognizes are overrepresented in the fragments identified as bound by AGL15. Currently we are focusing on confirmation of select direct targets of AGL15 (and the redundant AGL18) and to determine the function of regulated genes.
Finally we are developing tools to allow us to extend the gene regulation network underlying embryogenesis by looking at genes regulated by some AGL15 targets that encode transcriptional regulators. The data obtained has also led to an ongoing collaboration with a researcher at the University of Wisconsin-Madison.
A full-day workshop entitled "A short-course on seed dormancy and germination with emphasis on Hawaiian species" University of Hawaii, Manoa.
Half-day workshop entitled "Future research objectives for studies on seed dormancy and germination in the Junggar Desert, northwest China." Xinjiang Agriculture University, Urumqi, China.
Lecture: "Seed dormancy profile for the Xishuangbanna Tropical Seasonal Rainforest Dynamics Plot: First approximation" Chinese Academy of Sciences, Xishuangbanna Tropical Botanical Garden, Kunming, China.
Lecture. "Variation in seed dormancy/germination within and between individuals and populations" Chinese Academy of Sciences, Xishuangbanna Tropical Botanical Garden, Kunming, China.
Lecture. " The ecology of the federally-endangered species Solidago shortii" Xinjiang Agricultural University, Urumqi, China.
Lecture. "How seed dormancy studies serve plant conservation: Using information on biogeography and phylogeny of seed dormancy to facilitate propagation of plant species for restoration" Lyon Arboretum, University of Hawaii, Manoa.
Symposium talk. "Seed dormancy and germination of Hawaiian montane species: meeting common goals of basic science and conservation" Hawaii Conservation Conference, Honolulu, HI.
Lecture. "Seed germination ecology in a specific habitat: Cedar glades" Xinjiang Agricultural University, Urumqi, China.
Lecture. "Seed dormancy and germination of cedar glade plants" Cedars of Lebanon Annual Wildflower Weekend, Lebanon, TN.
Invited poster. "Classification and phylogeny of seed dormancy", Xishuangbanna International Symposium II.
Biodiversity Conservation: Research Imperatives for Scientific Institutions" Chinese Academy of Sciences, Institute of Botany, Xishuangbanna Tropical Botanical Garden, Menglum (Yunnan Province), P. R. China. The membership was expanded, an official name for the W-2168, that will not change each time we go through a re-write, was adopted, a webpage for the group was established.
We have now published our results adding to an emerging picture of direct transcriptional control. We have found, as have others, that while many sites are occupied by a given transcription factor in vivo (generally 1000s of DNA binding sites), relatively few interactions between a transcriptional regulator and DNA result in significant changes in gene expression of the nearby gene.
Analysis of genes directly and indirectly controlled by AGL15 has led us to investigate hormone interactions involved in control of somatic embryo development. We are currently using combinations of mutants, hormones and inhibitor treatments to tease apart how different hormoneal cross-talk controls somatic embryo development. We have extended our work in Arabidopsis and demonstrated that ectopic expression of AGL15 in soybean can promote somatic embryogenesis in this important crop.
Chen, Tingsu, Nayak, Nihar, Maitra Majee, Susmita, Lowenson, Jonathan, Schafermeyer, Kim R., Eliopoulos, Alyssa C., Lloyd, Taylor D., Dinkins, Randy, Perry, Sharyn E., Forsthoefel, Nancy R., Clarke, Steven G., Vernon, Daniel M., Zhou, Zhaohui Sunny, Rejtar, Tomas, and Downie, A. Bruce. 2010. Substrates of the Arabidopsis thaliana PROTEIN ISOASPARTYL METHYLTRANSFERASE 1 identified using phage display and biopanning. Journal of Biological Chemistry. 285: 37281 to 37292.