Atmospheric carbon and climate change. Tackling climate change by enhancing carbon sequestration potential through improving photosynthetic efficiency
Peggy G. Lemaux, Cooperative Extension Specialist
Plant and Microbial Biology
Closed. This professor is continuing with Fall 2023 apprentices on this project; no new apprentices needed for Spring 2024.
General Description
Are you facing unusual heat waves or increased rainfall where you or your family live? Every country is facing the effects of climate change. They are not limited to heatwaves but also include changes in rainfall, more severe and frequent storms, increased threat of wildfires and more severe drought. All these factors are projected to have negative effects on crop yields and cause food security issues worldwide (Jägermeyr et al., 2021 https://doi.org/10.1038/s43016-021-00400-y). Greenhouse gases, e.g., CO2, and methane, are culprits for these changes. One approach to address this issue is to capture larger amounts of atmospheric carbon to reduce atmospheric CO2, hoping to slow or perhaps even reverse global warming. Plants, as a bio-factory, capture atmospheric carbon through photosynthetic CO2 fixation and store it through carbon sequestration, primarily in its roots. So, plant genetic engineering and genome editing can be used to increase carbon-sequestration.
Several studies have demonstrated the success of this approach in various plant species. The goal of our laboratory is to identify potential genes to improve CO2 fixation and use genetic engineering or genome editing to improve carbon sequestration through improved photosynthetic efficiency and increased root biomass. This ambitious project is in collaboration with Professors David Savage at the IGI and Krishna Niyogi in PMB. The ultimate target of our carbon sequestration efforts is Sorghum bicolor, the fifth most widely grown cereal crop worldwide. Sorghum is an attractive multipurpose crop in drought and flood-prone regions as it is a source of food, feed, and fuels, as a bioenergy feedstock. Compared to C3 photosynthesis used in crops like rice and wheat, sorghum uses the more efficient C4 photosynthetic pathway, that results in higher CO2 fixation into sugar. Sorghum is also attractive as it has a high adaptability to a wide range of environmental conditions, like heat and soil water deficit, suggesting it is one of the most promising crops for future adverse environments (Aydın-Kandemir et al., 2022 https://doi.org/10.1016/j.indcrop.2023.116776).
As a research subject, sorghum’s seed to seed lifecycle is ~4.5 months, making it difficult to make rapid progress in determining the function of genes involved in photosynthetic efficiency and biomass production. To accelerate the research effort, initial screening of gene function can be done in Setaria viridis, a C4 grass with a shorter 7-8 week lifecycle. Several approaches have been used to identify genes of interest for our efforts. One is to use sorghum protoplasts to screen for successful genome edits in a high-throughput assay. From those candidate edits, the most promising ones will be further evaluated with editing or overexpression constructs to stably transform into sorghum or Setaria. Engineered or edited plants will be analyzed using molecular, physiological and biochemical assays. Another approach to identify candidates is literature screening to identify genes, shown to be involved in improved photosynthesis or deeper or larger root structure, that were demonstrated in the same plant species or a phylogenetically close relative. Through this process, to date we have focused on two genes, Raf1 (rubisco accumulation factor) and Zmm28 (MADS-box transcription factor). Raf1 genetically engineered plants have already been generated and are being analyzed at the molecular and physiological levels. Use of a Zmm28 expression construct in sorghum is expected to lead to moderate constitutive Zmm expression (see below). Other constructs are being identified to improve editing efficiency.
One of the challenges of doing engineering and editing in crop plants, like sorghum, is efficiency. Recent advances were made to address these issues, using developmental genes during the transformation process. Using this approach, our lab has improved sorghum transformation efficiency from 1-3%, using classical immature embryo transformation, to nearly 50%, using developmental genes, Bbm and Wus (Aregawi et al. 2021. doi:10.1111/pbi.13754). Using this approach, a construct, in which Zmm28 is being driven by a rice GOS2 promoter to achieve moderate constitutive expression, was introduced into Agrobacterium tumefaciens that was used to infect sorghum immature embryos. Two such experiments are underway – involving movement of tissues from callus induction to regeneration medium and finally to rooting medium. Regenerated plantlets will be genotyped by PCR to confirm the presence of Zmm28. 10-20 independent events will be identified, and copy number determination analysis will be conducted to identify single-copy lines. Western blot analysis will be performed to confirm and determine relative expression levels of Zmm28 protein. Next, selected Zmm28-positive, single-copy lines will be generation-advanced and measurements of photosynthetic efficiency will be performed on transgenic first-generation and ultimately second-generation lines versus a control null segregant line. The goal of this URAP project is to identify single-copy, transgenic Zmm28 lines and, time permitting, conduct photosynthetic measurements in collaboration with the Niyogi lab.
Role: The interests and skill level 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, which include molecular cloning, transformation of sorghum or Setaria and molecular analyses of transgenic plants. The student may also care for plants in growth chambers and the greenhouse, collect experimental materials and data when necessary. The student will work directly with a postdoctoral fellow, a staff research associate, other undergraduates and the principal investigator. Student will participate in lab meetings and contribute to presentations and publications, as appropriate. The time commitment required will be negotiated with the student. Day-to-day supervision for this project will be by postdoctoral scholar, Dr. Sultana Anwar.
Qualifications: Willingness to learn new techniques and enthusiasm for research are necessary; previous laboratory experience outside the classroom is desirable. Care-to-detail and commitment to scheduled work times are critical.
Day-to-day supervisor for this project: Sulltana Anwar, Post-Doc
Hours: to be negotiated
Related website: https://plantandmicrobiology.berkeley.edu/users/peggy-g-lemaux
Biological & Health Sciences