Peggy G. Lemaux, Cooperative Extension Specialist

Closed (1) Investigation of the transcriptional networks that coordinate drought response in sorghum

Closed. This professor is continuing with Spring 2021 apprentices on this project; no new apprentices needed for Fall 2021.

GENERAL DESCRIPTION
The C4 cereal, sorghum (Sorghum bicolor L. Moench), the fifth most important cereal crop worldwide, is a critical food, forage, and emerging biofuel crop that is notably drought-tolerant. Understanding the mechanisms by which sorghum is able to survive drought is critical for efforts to improve agricultural yields in sorghum and other crops under climate change scenarios that come with increasingly frequent drought periods. In a large DOE-funded project we grew sorghum in the field under water-limiting conditions, taking weekly samples of roots and leaves, and then performed transcriptional profiling. This data revealed that 44% of expressed genes were significantly affected after drought was imposed – either before or after plants flowered. These alterations included dramatic changes in well-known drought pathways and also many unknown pathways. Based on the results we got from transcriptomic data, we chose two transcription factors, which are belonging to the NAM, ATAF, and CUC (NAC) gene family and MYB gene family, as candidate genes contributing to drought tolerance.
In our studies we found that there was large-scale depletion in expression of certain genes critical to gene regulation during drought. We found out that two types of transcription factors in the NAC and MYB genes families were expressing differently during drought and recovery following re-watering. In studies by others, a NAC transcription factor, named D/dry/SbNAC_D, was found to encode a master transcriptional switch that induces programmed death of pith parenchyma cells in the sorghum culm. We believe it is probably involved in sorghum root development during its drought response. Another transcription factor MYB, the orthologous gene of R2R3-MYB? in Arabidopsis, is involved in the regulation of stomatal movement. Investigating the roles of these two transcripitonal regulators may provide insights into mechanisms of drought response in sorghum and reveal possible mechanisms in the drought tolerance pathway.
Current efforts in the lab are focused on understanding the precise role of these genes in drought responses. Critical genes will be identified from these genes and strategies to engineer and edit those genes will be developed to try to develop a better understanding of their role in sorghum’s response to drought. Former and current Lemaux lab members have focused on developing more efficient engineering and editing strategies for sorghum, using newly developed methods involving the introduction of Wushel and Babyboom genes that reset the developmental pathway of transformed cells. These approaches have expanded the number of sorghum varieties that can be transformed and increased the efficiency of introducing target genes.
Efforts to develop proper constructs to engineer and edit sorghum with key genes involved in drought tolerance and introducing them into sorghum will be launched during spring 2021. Once sorghum transformants are generated, seedlings will be tested by PCR to confirm the presence of the transgene and that modification of the target genes has been achieved. Once appropriate transgenic lines are identified, analyses will be conducted to assess effects of overexpression and knock outs of the genes on phenotypic, biochemical and molecular characteristics of the transformed plants. The analysis of gene function will provide more insights into the nature of gene regulation networks under drought conditions.

GOALS OF PROJECT
The long-term objectives of this project are to understand the mechanisms of increased drought tolerance in sorghum and the importance of its association with gene regulation in order to learn more about these mechanisms. This phase of the project involves the generation of constructs and introducing them into sorghum. These efforts will give us more information to inform future sorghum gene engineering and editing and may provide information for a peer-reviewed publication.


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 be involved in the Sorghum project. This could include molecular cloning, gRNA design, transformation of sorghum and molecular analyses of transgenic plants using PCR etc. The student will work with a postdoc, research assistants, other undergraduates and the principal investigator. Students will also participate in lab meetings and contribute to presentations.

Day-to-day supervisor for this project: Jianqiang Shen, Postdoctoral fellow


Day-to-day supervisor for this project: Jianqiang Shen, Post-Doc

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 important

Weekly Hours: to be negotiated

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