Te research focus of my lab is on secondary metabolite biosyntheses and functions. oliver yu, ph.d. associate member oyu@danforthcenter.org


Flavonoids are a group of ubiquitous and diverse small molecules synthesized by the phenylpropanoid pathway in higher plants. Teir functions in plant-microbe interactions and defense responses have been well established. We continue to investigate the functions of flavonoid compounds in root development. Previous experimental data suggested that flavonoids could also regulate auxin transport. We showed that isoflavones in soybean and flavonols in Medicago trun- catula could block auxin transport during root nodule development. However, the mechanisms behind this activity have not been defined.


We discovered recently that regulation of auxin transport by flavon- oid compounds might be linked to the expression of auxin-related micrornas (mirna). Previously, we have identified a number of mirna’s from soybean roots that were up- or down-regulated in re- sponse to Bradyrhizobium japonicum infection. Of particular interest were several families of mirnas implicated in auxin actions. Over- expression of these mirna’s led to increased or decreased nodule and lateral root numbers; while constitutive silencing of the genes targeted by these mirna’s led to similar phenotypes. Additional experiments confirmed that this group of auxin-related mirna’s was essential for both lateral root and nodule development.


Furthermore, we investigated the functions of the same group of mirna’s in m. truncatula root development. Unlike soybean, Medica- go belongs to indeterminate nodulating plants that are more sensitive to auxin transport during nodulation. Over-expression of some of the mirna’s led to similar nodulation phenotypes as observed in soybean. Other mirna’s showed different phenotypes. Tese results confirmed that auxin-related mirna’s were important for both determinate and indeterminate nodulating plants.


We studied soybean xylem sap proteins and searched for signal peptides that are responsible for controlling root and nodule development under different environmental conditions. Te 2-D gel electrophoresis of soybean xylem sap proteins was shown here. Te protein spots were later iden- tified by Mass Spectrometry with the help from Dr. Leslie Hicks’ group at the Danforth Plant Science Center.


We also completed a set of experiments investigating the so-called “soybean-specific” mirna’s. Tese mirnas were specifically induced during nodulation but had not been reported previously. We found interesting nodulation phenotypes when these mirnas were over-ex- pressed under the control of a constitutive promoter or a nodulation- inducible promoter. We are focusing on identification and analysis of the target genes of these novel mirna’s.


lab members: Hui Chen, Research Scientist / Ying Deng, Post- doc Research Assistant / Yechun Wang, Postdoc Research Assitant Satish Guttikonda, Former Postdoc Research Assistant, currently Dow AgroSciences. / Rui Zhong, part time technician


recent publications: Gutierrez-Gonzalez ,J.J., Wu, X., Gillman, J.D., Lee, J.D., Zhong, R., Shan- non, J.G., Yu, O., Nguyen, H.T., Sleper, D.A. (2009) Intricate environment- modulated genetic networks control isoflavone accumulation in soybean seeds. BMC Plant Biology. (accepted).


Yu, O., Wang, Y. (2009) Te functions of flavonoids during legume-rhizobia in- teractions. In Ecological Aspects of Nitrogen Metabolism in Plants. Joe Polacco and Chris Todd (eds). (accepted).


Yamaguchi, M., Valliyodan, B., Zhang, J., Lenoble, M.E., Yu, O., Rogers, E.E., Nguyen, H.T., Sharp, R.E. (2009) Regulation of growth response to water stress in the soybean primary root. I. Proteomic analysis reveals region specific regula


page 22 2009 scientific report the donald danforth plant science center


tion of phenylpropanoid metabolism and control of free iron in the elongation zone. Plant Cell Environment. (in press).


Subramanian, S., Cho, U.H., Keyes, C.A., Yu, O. (2009) Proteomic analysis of soybean xylem sap in response to symbiotic and pathogenic interactions. BMC Plant Biology 2009, 9:119. (http://www.biomedcentral.com/1471-2229/9/119 ).


Gutierrez-Gonzalez, J.J., Wu, X., Zhang, J., Lee, J.D., Ellersieck, M., Shannon, G.J., Yu, O., Nguyen, H.T., Sleper, D.A. (2009) Genetic control of soybean seed isoflavone content: Importance of statistical model and epistasis in com- plex traits. Theoretical and Applied Genetics 119: 1069-1083.


Keyes, C.A., Subramanian, S., Yu, O. (2009) Hairy root as a model system for undergraduate laboratory curriculum and research. Bioscene 35: 6-12.


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36