Outreach web site: ucbiotech.org
Ph.D. University of Michigan, 1977
B.S. Miami University, 1968
Research objectives of the Lemaux Lab include development and use of genetic transformation systems for monocotyledonous species, such as the cereals, Triticum aestivum, Zea mays, Avena sativa, Hordeum vulgare, and Oryzae sativa, and the grasses, Festuca spp., Dactylis glomerata, and Poa pratensis. Our long-term objective is to use transformed cereals to explore basic biological questions as well as to understand and improve crop characteristics.
Use of genetic engineering strategies to understand and improve cereals and grasses
The Lemaux laboratory’s focus is on the development and use of genetic engineering and genomic strategies for monocotyledonous species, such as the cereals, 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 identify gene function, to explore basic biological questions in these species and to use this information to improve crops.
Methods for stably transforming cereal and grass species are more routine today than two decades ago, but 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 has been successful for model genotypes but has been challenging for commercially important varieties. For this reason, our laboratory developed other culturing methods, including new target tissues, like cultured adventitious meristems (left) and highly regenerable, green tissue (right), a developmental stage between embryogenic and organogenic. To develop these methods required a more detailed understanding of the biological nature of the in vitro response of target tissues, accomplished with in situ hybridization, using antibodies to key developmental proteins, knotted1 and leafy cotyledon1 (Zhang et al., 1998, 2002a).
Using these methods, we developed efficient transformation systems for 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; Gurel et al., 2009). Resultant transgenic plants were studied using cytogenetic analysis (Choi et al., 2000) and methylation polymorphism to ameliorate the underlying causes of somaclonal variation (with P. Bregitzer, USDA, Aberdeen ID; Bregitzer et al., 1998; 2002). We decreased transgene expression instability in barley using maize transposable elements as gene delivery vehicles. Unlike bombardment-mediated events where transgenes in most transgenic lines were silenced by the third generation, the majority of transposon-delivered transgenes had stabilized gene expression following generation advance (Koprek et al., 2000, 2001). Counteracting effects of apoptosis with heat treatment after Agrobacterium infection (left), sorghum transformation frequency increased to ~8% (Gurel et al., 2009).
Another lab focus relates to functional genomics. For these efforts in barley, we used the maize transposable element, Ds, and the transposase gene. When these two elements come together in the same plant, Ds is activated and transposes to new genomic locations, preferentially into genic regions. The inverted repeat regions of Ds sequence are then used for inverse PCR to sequence flanking DNA, identify the gene into which Ds inserted and to map its location
(Cooper et al., 2004; Singh et al., 2006). One gene tagged by this approach was a wall-associated kinase (WAK) gene, a 125-member family in rice (Zhang et al., 2005) involved in biotic and abiotic stress tolerance (with Z-H He, San Francisco State). Efforts to identify additional tagged genes in barley continue (J. Singh (McGill, Montreal Canada; P. Bregitzer, USDA-ARS, Aberdeen ID). More recent functional genomic efforts in our laboratory in sorghum have focused on naturally occurring transposable elements, like Mu-like elements, to develop a homologous transposable element system to identify gene function (with D. Lisch, UCB).
With effective transformation methods in hand, transgenic cereals were created that over- and under-express the natural redox protein, thioredoxin, and its companion enzyme, 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 transgenes to the protein bodies of the endosperm (Cho et al., 1999b). Homozygous Trx h5 transgenic seeds of barley germinated faster, alpha-amylase levels rose earlier and levels of the starch-degrading enzyme, pullulanase, were higher (Cho et al., 1999) - useful traits for the malting industry. Given that changes engineered in the endosperm, once thought to be a “dead” tissue, caused changes in the embryo and the aleurone revealed the likelihood of a redox communication network mediated by thioredoxin
(Wong et al., 2002).
In wheat homozygous lines overexpressing Trx h5 had lowered allergenicity in the gliadin fraction, as assessed using a canine model (Li et al., 2009), and improved dough quality with poor quality wheat flour (unpublished). Building on this work, Chinese collaborators used an antisense construct for trx h9 to determine if this could mitigate the devastating problem of preharvest sprouting. In general, underexpression of Trx h showed effects on germination and associated enzymes that were opposite those with Trx h5 overexpression in barley. Importantly, grain in the transgenic head resisted sprouting 7d following humidity treatment, while nontransgenics sprouted (right) (Li et al., 2009). From two years of field grown data, yield and quality properties of both transgenic lines were generally affected positively in both a low-gliadin and a high-gliadin variety.
Just as earlier evidence in barley showed, a change in the endosperm caused effects in the embryo and aleurone. To begin to unravel the communication network, work was initiated in Arabidopsis that showed thioredoxin, trxh9, unlike other thioredoxins, is located in the cell membrane and may function in cell-to-cell communication of redox state
(Meng et al. 2010). IThis could provide the communication mechanism between the endosperm and the embryo and aleurone. Future work will focus on using proteomics and transcriptomics to continue unraveling the redox communication network.
More recently, overexpression of Trx h5 was accomplished in sorghum and appears to lead to improved digestibility (Wong et al., unpublished). This is important because, of all cereals, sorghum flour is the least digestible, particularly after cooking. The digestibility work in sorghum, in addition to efforts to include improving sorghum transformation efficiency (Gurel et al., 2008), were initiated as a part of the Bill and Melinda Gates Grand Challenges for Global Health (http://www.supersorghum.org/). Current efforts also are focused on perfecting a transformation technology for sweet sorghum, to be used in further developing this crop as a potential bioenergy source. Another effort in sorghum is aimed at establishing a mechanism to generate a doubled haploid population in sorghum, modified from a published technology in Arabidopsis (with S. Chan, UC Davis).
In order to further optimize gene function studies in cereals, we are attempting to develop transformation technologies for green foxtail (Setaria viridis; right), a fast-cycling, diploid C4 monocot grass and a green moss (Physcomitrella patens; left), which shares fundamental genetic and physiological processes with vascular plants but has the advantage of possessing an efficient homologous recombination system.
The latest project in the Lemaux Lab is a collaborative project between UC Berkeley, Lawrence Berkeley National Laboratory, Joint Genome Institute and University of Kentucky researchers and is funded by DOE’s ARPA-E PETRO (Plants Engineered To Replace Oil) Program. The goal of the FOLIUM project is to develop tobacco as a platform for foliar production of advanced hydrocarbon fuels. This involves installing pathways for alkane and isoprenoid biosynthesis and accumulation in tobacco leaves via chloroplast and nuclear transformation. In addition, optimizing carbon flux toward hydrocarbon biosynthesis, enhancing photosynthetic light efficiency and CO2 uptake and increasing tobacco biomass production by improving planting, cultivation and harvesting practices are also goals. To achieve foliar production of oil and oil-based biofuels, tobacco (Nicotiana tabacum) was chosen for several reasons. It is a very productive biomass crop with large leaf surface area, and a high leaf-to-stem ratio. It can also be harvested multiple times per year and there is already large-scale infrastructure in place for planting, growing, harvesting and handling tobacco. In addition tobacco is cultivated on large acreages in the US and in over 100 countries worldwide. It can be cultivated on marginal lands, has a wider geographic planting range than corn or sugar cane and is not part of the food supply chain. Important to the achievement of FOLIUM’s scientific objectives, tobacco is highly amenable to genetic and molecular manipulations of both nuclear and plastid genomes. With 500 to 10,000 plastids per cell, there is potential for very high overexpression of selected genes. The goals of the Lemaux laboratory is to install the myriad constructs responsible for achieving the multitude of goals for this project. This involves both chloroplast and nuclear transformation and generation advancing and characterizing the independent lines. In addition to the FOLIUM project, the laboratory is also engaged in a project to improve the biofuel characteristics of sorghum in collaboration with other university and company researchers.
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, including biotechnology, on food and agriculture. I develop 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. The focus on science-based assessments to address issues raised about modern agriculture led to 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, with my administrative assistant (B. Alonso), have also created other educational resources, like games, displays, videos and curricula. One curriculum, aimed at middle school students in afterschool, is DNA for Dinner (http://ucbiotech.org/dnafordinner). Another curriculum is aimed at the development of a STEM-based 3-D gaming environment to engage players' interests in biology (with D.Gilchrist, B. Soots, UC Davis). I give numerous lectures in local, state, national and international venues and serve on a number of local, state and national committees relating to biotechnology and agriculture. I am presently or was 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.
Ren, J.-P., Li, Y., Wong, J.H., Meng L., Cho, M-J., Buchanan B.B., Yin, J. and Lemaux P.G. 2012. Modifying Thioredoxin Expression in Cereals Leads to Improved Pre-Harvest Sprouting Resistance and Changes in Other Grain Properties. Seed Science Research 22: S30-S35.
Meng, L., Wong, J.H., Feldman, L.J., Lemaux, P.G. and Buchanan, B.B. 2010. A membrane-associated thioredoxin required for plant growth moves from cell to cell, suggestive of a role in intercellular communication. Proceedings of the National Academy of Sciences USA 107: 3900-5.
Meng, L., Zhang, S. and Lemaux, P.G. 2010. Developing a Molecular Understanding of In Vitro and In Planta Shoot Organogenesis. In: Plant Tissue Culture, Development and Biotechnology. Trigiano, R. N. and Gray, D. (eds.), CRC Press, pp. 259-278.
Meng, L., Zhang, S. and Lemaux, P.G. 2010. Toward Molecular Understanding of In Vitro and In Planta Shoot Organogenesis. Critical Reviews of Plant Sciences 29 (20): 108-122.
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.
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.
Lemaux, P.G. 2010. What's Slowing Commercialisation of GE Crops? Regulatory, Economic, Intellectual Property and Consumer Acceptance Issues. In '1st Australian Summer Grains Conference'. Gold Coast, Australia. (Eds B George-Jaeggli, DJ Jordan). (Grains Research and Development Corporation).
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.
Lemaux P.G. 2007. “Do We Need Genetically Modified Foods to Feed the World? A Scientific Perspective”. In: Realities of Nutrition, 3rd Edition. Morrill JS and Deutsch RM. Orange Grove Publishing, Menlo Park CA, pp. 268-270.
Honors and Awards
American Society of Plant Biologists Excellence in Education Award, 2012
President, American Society of Plant Biologists, 2011
Society for In Vitro Biology 2010 Lifetime Achievement Award - Society for In Vitro Biology - 2010
Fellow - Crop Science Society of America - 2007
Distinguished Service Award, Outstanding Outreach - Cooperative Extension Academic Assembly Council, Division of Agriculture and Natural Resources - 2006
Dennis R. Hoagland Award for outstanding contribution to agricultural research - American Society of Plant Biologists - 2003
Fellow - American Association for the Advancement of Science - 2002
Distinguished Service Award, Outstanding Research - Cooperative Extension Academic Assembly Council, Division of Agriculture and Natural Resources - 1997
Honored Women of the University of California, Berkeley - UC Berkeley - 1995