The seminar provided a compelling and informative exploration of the future of plant biotechnology and its potential to enhance food security under increasingly variable environmental conditions.
During her presentation, Professor Ngara discussed the complex ways in which crops adapt to environmental stress, focusing on sorghum as a model species due to its natural drought tolerance and genetic diversity.
Her research integrates traditional plant physiology with advanced omics technologies – including proteomics, metabolomics, and transcriptomics – to uncover the molecular changes that occur in plants under abiotic stress conditions such as drought, salinity and heat. By combining these technologies with bioinformatics, her team analyses extensive datasets to map the interactions of molecules within stressed plant systems.
"Sorghum was selected for its high drought resilience and the availability of its genome sequence, which was completed in 2009. In 2014, we published an opinion piece advocating for the use of sorghum in abiotic stress studies."
She explained that her team conducts comparative analyses between drought-tolerant and susceptible sorghum lines to examine their molecular and physiological responses, and further described how cell suspension cultures were developed from sorghum callus tissue to study secreted proteins, known as the secretome, which play key roles in signalling and protection against external stressors.
"Of the seven genotypes tested for this culture development, only the ICSB 338 variety yielded a friable callus suitable for creating suspension cultures. These in vitro systems provide a controlled environment for investigating how sorghum cells respond to drought at the protein level." Physiological assessments conducted in soil potting experiments revealed significant differences between the susceptible variety (ICSB 338) and the tolerant variety (SA 1441). After three weeks without watering, ICSB 338 showed severe wilting and ultimately died, while SA 1441 remained green and vigorous.
Measurements of relative water content, chlorophyll levels, stomatal conductance, and leaf surface temperature confirmed the superior stress resilience of the tolerant variety, which also demonstrated improved recovery following rewatering.
Seminar attendees engaged with data delivered by Professor Ngara.
Uncovering Molecular Mechanisms Behind Drought Tolerance
Professor Ngara also emphasised osmolyte accumulation as a critical element of drought response. Osmolytes such as proline and glycinebetaine act as protective molecules, stabilising cellular structures and enzymes during stress. Through time-course experiments, her team found that the tolerant variety began accumulating these compounds earlier than the susceptible one. "This early response was associated with the activation of key drought-responsive genes, as revealed through quantitative PCR analysis."
One of the most innovative aspects of her research involved proteome analysis using two advanced techniques: two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) for protein separation and isobaric tags for relative and absolute quantitation (iTRAQ) for protein quantification. These methods enabled the identification of over 1 000 proteins across both sorghum varieties, many of which were differentially expressed under drought conditions.
The results revealed marked differences in protein expression patterns between the tolerant and susceptible genotypes. She placed particular focus on the roles of proteases and protease inhibitors during drought stress. Proteases are enzymes that degrade proteins and are essential for nitrogen recycling, programmed cell death and overall protein turnover – processes that are often heightened under stress.
Her findings showed that the tolerant variety exhibited lower proteolytic activity and increased expression of protease inhibitors, contributing to protein stability during drought. Conversely, the susceptible variety showed elevated protease activity and reduced protein content, indicating greater cellular degradation.
"The results from heat stress experiments noted that ICSB 338 cells demonstrated resilience under 40°C conditions for up to 72 hours, while Arabidopsis cells showed an 80% reduction in viability after just 24 hours. The sorghum cells upregulated heat shock proteins, suggesting the presence of adaptive heat stress responses alongside drought tolerance."
Bridging Lab Research with Agricultural Practice
In closing, Professor Ngara emphasised the importance of bridging the gap between laboratory-based molecular research and real-world agricultural applications. She called for stronger collaborations with research groups working in field physiology and functional genomics, and highlighted the need for increased funding to support the high costs associated with omics technologies.
She also encouraged expanded field studies examining plant physiology, yield components, and below-ground traits across multiple cereal species, using tools such as phenomics.
Attendees were urged to contribute to special issues Professor Ngara is editing in Plants (Plants | Special Issue : 'Omics' and 'Multi-Omics' Insights into Plant Responses to Abiotic Stresses) and in Frontiers in Plant Science (https://www.frontiersin.org/research-topics/68362/omics-applications-for-pathogen-control-and-disease-resistance and Frontiers | The Plant Extracellular Matrix: Dynamics in Composition and Function in Response to Biotic and Abiotic Stresses), expressing her hope that continued research will contribute to the development of more climate-resilient crops.
Story by Cleopatra Makhaga. Pictures supplied.