Peggy G. Lemaux

Cooperative Extension Specialist
Ph.D.  University of Michigan, 1977
B.S.   Miami University, 1968

411B Koshland Hall
Berkeley, California 94720
lemauxpg@berkeley.edu
office: 510-642-1589   lab: 510-642-1347   fax:  510-642-7356

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Research Interests

The Lemaux laboratory’s focus is on the development and use of genetic engineering and genomic strategies for monocotyledonous species, such as wheat (Triticum aestivum), sorghum (Sorghum bicolor), barley (Hordeum vulgare), rice (Oryza sativa), maize (Zea mays) and certain grass species, like Festuca spp., Dactylis glomerata, and Poa pratensis. Our long-term objectives are to transform cereals and grasses to explore basic biological questions and to use this information to improve crops.

Methods for stably transforming cereal and grass species are more routine today than a decade ago, although challenges still exist. Nearly all methods utilize in vitro-derived tissue culture materials, which leads directly or indirectly to limitations in varieties that can be transformed, to somaclonal variation and to transgene expression instability.

Most cereal transformation efforts involve culturing immature embryos to obtain embryogenic or organogenic tissue. This approach was often successful for model genotypes but not commercially important varieties. For this reason, we developed other culturing methods, including new target tissues, like cultured adventitious meristems and green tissue (below right), a developmental stage between embryogenic and organogenic.

To accomplish these developmental manipulations required developing a better understanding of the biological nature of the in vitro response of target tissues. This was accomplished with in situ hybridization, using antibodies to key proteins, like knotted1 and leafy cotyledon1 (Zhang et al., 1998, 2002a). This approach provided tools to better define the developmental state of the tissue.

Based on these efforts we developed efficient transformation methods for many previously recalcitrant varieties of wheat, barley, corn, rice, oat, sorghum and forage and turf grasses (e.g., Cho et al., 1998, 1999a; Ha et al., 2000; Cho et al., 2000a; Cho et al., 2000b; Zhang et al., 1999, 2002b). Resultant transgenic plants were studied using cytogenetic analysis (Choi et al., 2000) and methylation polymorphism to identify and ameliorate the underlying causes of somaclonal variation (with P. Bregitzer, USDA, Aberdeen ID; Bregitzer et al., 1998; 2002). Transgene expression instability was addressed using maize transposable elements as gene delivery vehicles. In barley we showed that the majority of transgenes delivered via this method had stabilized gene expression during generation advance (Koprek et al., 2000, 2001). Counteracting the effects of apoptosis following Agrobacterium infection by heat treatment, we increased sorghum transformation frequency to nearly 8% (Gurel et al., 2008).

Another focus of the lab relates to functional genomics efforts in barley that provide information for other large genome cereals, like wheat. We introduced into barley the maize transposable element, Ds, and the transposase gene. When individual plants were crossed, Ds was activated and transposed to new locations in the genome with  preference to insert into genic regions – an advantageous trait for large genome species. Using the Ds sequence as a tag, the sequence can be used as a priming site to identify the gene into which Ds transposed and to map its location (Cooper et al., 2004; Singh et al., 2006). By identifying Ds elements that map close to phenotypes or genes of inte rest the element can be reactivated and Ds generally will transpose to nearby locations. One gene tagged by this approach was a wall-associated kinase gene or WAK, shown to be a 125-member family in rice (Zhang et al., 2005) that, based on studies in Arabidopsis, is involved in biotic and abiotic stress tolerance (with Z-H He, San Francisco State).

The transformation methods were used to over-express in transgenic cereals the natural redox protein, thioredoxin, and its companion, NADP thioredoxin reductase (with B. Buchanan, UCB). To achieve maximal over-expression in the grain, we used seed-specific promoters and vacuolar targeting to direct the transgene to the endosperm (Cho et al., 1999b). Homozygous transgenic seeds of barley germinated faster and alpha-amylase levels rose earlier (Cho et al., 1999), useful traits for the malting industry. Experiments with the transgenic barley grains also revealed evidence that the starchy endosperm, once thought to be a “dead” tissue, can communicate with the embryo and the aleurone (Wong et al., 2002). In wheat homozygous lines overexpressing Trx h had lower allergenicity (Li et al., 2009) and improved dough quality (unpublished). Building on this work Chinese collaborators, using an antisense construct for trx h9¸were able to prevent preharvest sprouting (Li et al., 2009). This work was consistent with earlier evidence indicating communication channels exist between the endosperm and the embryo. In sorghum overexpression Trx h led to improved digestibility (Wong et al., unpublished). The work on sorghum, which also involves improving sorghum transformation efficiency (Gurel et al., 2008) and amino acid quality, was a part of the Gates Grand Challenges for Global Health (http://www.supersorghum.org/ ).

Outreach Interests

My faculty position, as a Cooperative Extension Specialist, mandates statewide responsibility for outreach and educational programming related to agriculture and foods. These efforts are designed to increase public understanding of agricultural practices, food production and the impact of new technologies on food and agriculture, including biotechnology. I am involved in the development of educational programming and resources that address these issues. This includes the development of an award winning, informational website, http://ucbiotech.org/ , intended to provide scientifically based information and resources to educators. This focus on a science-based approach to addressing the issues raised about modern agriculture led to the publication of two articles in Annual Review of Plant Biology, entitled “Genetically Engineered Crops and Foods: A Scientist’s Analysis of the Issues. Part I and II (Lemaux PG. 2008; 2009). I have also created other educational resources, like games, displays, and videos. I give large number of lectures in local, state, national and international venues and served on numerous local, state and national committees relating to biotechnology and agriculture. I am also involved in the education and extension efforts of several CSREES-sponsored Coordinated Agriculture Programs: Barley CAP, Conifer CAP, Rice CAP and Wheat CAP. Graduate students and postdoctoral fellows often participate in these efforts.

Lemaux, P.G. 2009. Genetically Engineered Plants and Foods: A Scientist's Analysis of the Issues (Part II). Annual Review of Plant Biology 60: 511–59.

Li, Y., Ren, J., Cho, M-J., Zhou, S., Kim, Y.B., Guo, H., Wong, J.H., Niu, H., Kim, H-K., Morigasaki, S., Lemaux, P.G., Frick, O.L., Yin, J., Buchanan, B.B. 2009. The Level of Expression of Thioredoxin is Linked to Fundamental Properties and Applications of Wheat Seeds. Molecular Plant 2: 430-441.

Lemaux, P.G. 2008. Genetically Engineered Plants and Foods: A Scientist's Analysis of the Issues (Part I). Annual Review of Plant Biology 59: 771-812.

Gurel, S., Gurel, E., Kaur, R., Wong, J., Meng, L., Tan, H-Q., Lemaux, P.G. 2008. Efficient, Reproducible Agrobacterium-mediated Transformation of Sorghum Using Heat Treatment of Immature Embryos. Plant Cell Reports (DOI 10.1007/s0029-008-0655-1).

Wong J.H., Lau T., Cai N., Singh J., Pedersen J.F., Vensel, W.H., Hurkman, W.J., Wilson, J.D., Lemaux, P.G., Buchanan, B.B. 2008. Digestibility of Protein and Starch from Sorghum (Sorghum bicolor) Is Linked to Biochemical and Structural Features of Grain Endosperm. Journal of Cereal Science 49: 73-82.

Zhang, S., Gu, Y.Q., Singh, J., Coleman-Derr, D., Brar, D.S., Lemaux, P.G. 2007. New insights into Oryza genome evolution: High gene colinearity and differential retrotransposon amplification. Plant Molecular Biology 64: 589-600.

Singh, J., Zhang, S., Chen, C., Cooper, L., Bregitzer, P., Sturbaum, A., Hayes, P. and Lemaux, P.G. 2006. High-frequency Ds remobilization over multiple generations in barley facilitates gene tagging in large genome cereals. Plant Molecular Biology 62: 937–950.

Gaj, M.D., Zhang, S., Harada, J.J. and Lemaux, P.G. 2005. Leafy cotyledon genes are essential for induction of somatic embryogenesis of Arabidopsis. Planta 222: 977-88.

Zhang, S., Chen, C., Li, L., Meng, L., Singh, J., Jiang, N., Deng, X.W., He, Z.H. and Lemaux, P.G. 2005. Evolutionary expansion, gene structure, and expression of the rice wall-associated kinase gene family. Plant Physiology 139: 1107-24.

Cooper, L.D., Marquez-Cedillo, L., Singh, J., Sturbaum, A.K., Zhang, S., Edwards, V., Johnson, K., Kleinhofs, A., Rangel, S., Carollo, V., Bregitzer, P., Lemaux, P.G. and Hayes, P.M. 2004. Mapping Ds insertions in barley using a sequence-based approach. Mol. Genet. Genomics 272: 181-93.

Cho, M.-J., Yano, H., Okamoto, D., Kim, H.K., Jung, H.R., Newcomb, K., Le, V.K., Yoo, H.S., Langham, R., Buchanan, B.B. and Lemaux P.G. 2004. Stable transformation of rice (Oryza sativa L.) via microprojectile bombardment of highly regenerative, green tissues derived from mature seed. Plant Cell Reports 22: 483-9.

Meng, L., Bregitzer, P., Zhang, S. and Lemaux, P.G. 2003. Methylation of the exon/intron region in the Ubi1 promoter complex correlates with transgene silencing in barley. Plant Molecular Biology 53: 327-40.

Choi, H.W., Lemaux, P.G. and Cho, M.J-. 2003. Long-term stability of transgene expression driven by barley endosperm-specific hordein promoters in transgenic barley. Plant Cell Reports 21: 1108-20.

Wong, J.H., Kim, Y.B., Ren, P.H., Cai, N., Cho, M.J., Hedden, P., Lemaux, P.G. and Buchanan, B.B. 2002. Transgenic barley grain overexpressing thioredoxin shows evidence that the starchy endosperm communicates with the embryo and the aleurone. Proceedings of the National Academy of Sciences USA 99: 16325-30.

Zhang, S., Wong, L., Meng, L. and Lemaux, P.G. 2002. Similarity of expression patterns of knotted1 and ZmLEC1 during somatic and zygotic embryogenesis in maize (Zea mays L.). Planta 215: 191-194.

Choi, H.W., Lemaux, P.G. and Cho. M.-J.. 2003. Use of flourescence in situ hybridization for gross mapping of transgenes and screening for homozygous plants in transgenic barley (Hordeum vulgare L.). Theoretical and Applied Genetics 106: 92-100.

Koprek, T., Rangel, S., McElroy, D., Louwerse, J.D., Williams-Carrier, R.E. and Lemaux, P.G. 2001. Transposon-mediated single-copy gene delivery leads to increased transgene expression stability in barley. Plant Physiology 125: 1354–1362.

Cho, M.-J., Choi, H.W., Lemaux, P.G. 2001. Transformed T0 orchardgrass (Dactylis glomerata L.) plants produced from highly regenerative tissues derived from mature seeds. Plant Cell Reports 20: 318-324.

Koprek, T.K., McElroy, D., Louwerse, J., Williams-Carrier, R. and Lemaux, P.G. 2000. An efficient method for dispersing Ds elements in the barley genome as a tool for determining gene function. Plant Journal 24: 253-263.

Choi, H.W., Lemaux, P.G., Cho, M.-J. 2000. Increased chromosomal variation in transgenic versus nontransgenic barley (Hordeum vulgare L.) plants. Crop Science 40:524-533.

Ha, C.D., Lemaux, P.G., Cho, M.-J. 2000. Stable transformation of a recalcitrant Kentucky bluegrass (Poa pratensis L.) cultivar using highly regenerative tissues. In Vitro Cellular and Developmental Biology 37: 6-11.

Cho, M.-J., Ha, C.D., Lemaux, P.G. 2000. Production of transgenic tall fescue and red fescue plants by particle bombardment of mature seed-derived highly regenerative tissues. Plant Cell Reports 19: 1084-1089.