Peggy G. Lemaux, Cooperative Extension Specialist

Closed (1) Increased Bioenergy Production in C4 Cereal Crops and Grasses

Applications for Spring 2018 are now closed for this project.

General Description

High biomass and starch content are important for bioenergy production from crop plants. In a 2015 study published by a collaborator, researchers demonstrated that introduction into rice of a plant-specific WRKY transcription factor, which regulates sugar-inducible gene expression, leads to plants with higher starch levels in seeds and stems and reduced methane emissions (Su et al., 2015. Nature 532: 602-608). This WRKY gene, barley SUSIBA2, when highly expressed, is associated with increased sink strength realized through changes in starch biosynthesis. Their transgenic rice lines were shown in the field to have methane emission levels reduced to 10% of that in control lines. Given that rice paddies are the largest anthropogenic source of methane, this alteration is important to lowering atmospheric methane, the second most important greenhouse gas next to carbon dioxide. This reduction is likely because SUSIBA2-induced transcriptional changes favor allocating photosynthate to aboveground biomass, starch in stems and seeds, rather than to below ground structures, namely the roots.

In addition to lowered methane emissions, transgenic rice lines had larger panicles with a higher proportion of filled grains and a smaller root system. The former was confirmed by measurements of increased aboveground grain dry biomass and numbers of filled grains. In contrast, plant height, thousand-grain weight and numbers of panicles and tillers per plant did not reveal any differences.

In this URAP project we are engineering SUSIBA2 into Setaria viridis, a model C4 grass, to test strategies for improving starch and biomass levels in an important C4 bioenergy cereal crop, Sorghum bicolor. Along side the Setaria work, we are using an identical strategy in sorghum. The reason that these two approaches are being pursued together is because the time to generate transgenic plants in Setaria is much shorter, ~6-8 weeks versus 4+ months for sorghum. Thus we can use Setaria as a quick screen to test approaches and determine efficacy of our strategies.

Former and current Lemaux lab members have completed preliminary work on this project, which involved creation of a construct with the selection gene, hptII, and the barley SUSIBA2 gene. Engineering efforts have generated a number of independent Setaria transformants and molecular analysis is underway. This work will continue during the 2018 school year. Plantlets will be tested by PCR to confirm presence of SUSIBA2 and, once confirmed, generation advanced to identify homozygous lines. Once homozygous lines are identified biochemical and phenotypic analyses will be conducted to assess effects of the expression of the WRKY gene on starch content in Setaria stems and seeds. This information will provide valuable information on its impact in this C4 grass and will provide complementary data to support the studies in sorghum.

Goals of Project
The long-term objective of this project is to increase starch content in seeds and stems of the C4 cereal, sorghum – an important bioenergy source with the environmentally important traits of drought and flood tolerance and fertilizer efficiency. This phase of the project involves the generation of engineered seeds in the model C4 cereal, Setaria viridis, while comparable lines are being generated and analyzed in transgenic sorghum. The efforts will provide important information for our sorghum studies, and may provide information for a peer-reviewed publication comparing effects in Setaria and sorghum.


The interests and skills of the student will dictate the specific duties and goals in which the student will be involved. The student will first learn basic techniques employed in the lab and will then become involved in the ongoing Setaria project. This could include in vitro culture and transformation of Setaria and molecular analysis of transgenic plants and seeds using PCR, fluorescence microscopy and bioinformatic analysis. The student’s duties might also include caring for plants and planting and harvesting seeds. The student will work directly with a laboratory assistant, other undergraduates and the principal investigator. Students will also participate in lab meetings and contribute to presentations and, as appropriate, publications.

Day-to-day supervisor for this project: Mary Madera, Staff Researcher

Qualifications: Enthusiasm for research is required; some laboratory experience outside of the classroom is desired. Ability to work easily with a diverse laboratory group is also desired. Junior preferred.

Weekly Hours: to be negotiated

Related website: http://plantandmicrobiology.berkeley.edu/profile/lemaux