Investigating photosynthetic mechanisms in model and non-model species

The impact of climate change is already evident, with record-breaking extreme temperatures, droughts, and altered rainfall patterns across the world. With these climate extremes and the need to supply food for the world, it is important to find novel ways to improve crop resilience. One approach is to increase photosynthetic efficiency in plants. This dissertation explores genetic and genomic changes in photosynthetic evolution and heat stress response. First, in Chapter 3, evolutionary mechanisms in wild grass species from the genus Steinchisma were studied using physiological, transcriptomic and metabolite comparisons between C3 proto-Kranz Steinchisma laxum and C2 S. hians. Key differences in transcriptome and metabolite profiles of the two species were observed, and evidence of a functional photorespiratory glycine shuttle and nitrogen rebalancing was seen in C2 S. hians using the combination of the transcriptome and metabolite profiles. In Chapter 4, an interspecific hybrid between S. laxum and S. hians was used to perform an allele-specific expression analysis (ASE) to identify cis- and trans-regulatory mechanisms controlling genes related to the evolution of photosynthesis in these two grass species, which showed that GDC-P and GDC-H exhibits cis+trans regulatory mechanism. SNPs associated with the NAD-ME also showed cis+trans regulation, which potentially contributes to its high expression in the early stages of the evolution of C4 photosynthesis. Finally, in Chapter 5, mutation in Rubisco activase 3 (rca3) showed that this gene is important in maize thermotolerance. The variability in response between the two genetic backgrounds used in this chapter also suggests variation in heat tolerance that could be utilized to study the interaction of rca3 with other genes and identify additional genes and loci for improving maize’s tolerance to heat stress. This research elucidated differences between S. laxum and S. hians at the transcriptome, metabolite and gene regulatory levels that could be key to evolution of photosynthesis in grasses and demonstrated the importance of rca3 in maize thermotolerance. Subsequent studies can build on these findings to improve crop resilience in important crop species.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Crop Sciences

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Mercado, Mae Antonette Gordola

Contributors dc:contributor

• Studer, Anthony J
• Ainsworth, Elizabeth A
• Sacks, Erik J
• Burgess, Steven J

• photosynthesis
• C2 photosynthesis
• C3 photosynthesis
• C4 photosynthesis
• C3-C4 intermediates
• Rubisco activase
• glycine shuttle
• heat stress

Statement dc:rights

• Copyright 2025 Mae Antonette Gordola Mercado

Language dc:language

en

Handle dc:identifier

https://hdl.handle.net/2142/132735

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/132735