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Mary Lou guerinot
Iron (Fe) is one of the essential micronutrients required by both plants and animals. In humans, Fe deficiency causes anemia, the most prevalent nutritional disorder in the world today. Most people rely on plant-based foods as their major Fe source, but plants are a poor source of dietary Fe.
Fe deficiency has many adverse effects on photosynthesis, which is not surprising given that 95% of foliar Fe is found in chloroplast. The Gueirnot lab had previously showed that the bHLH transcription factors ILR3 and PYE are required for photoprotection during Fe deficiency by preventing ROS damage to photosystem II (PSII). In order to identify the genes being regulated by these transcription factors, we employed RNA-seq analysis to generate genome-wide expression datasets for Arabidopsis thaliana wild type (WT), ilr3, and pye plants grown under Fe sufficient and Fe deficient growth conditions. We found a number of genes involved in PSII repair, PSII assembly and thylakoid membrane architecture that were mis-regulated in ilr3 and/or pye which may contribute to regulating photoprotection when plants are Fe deficient. We also identified other genes involved in the Fe deficiency response in shoots of A. thaliana. Our analysis provided evidence of a transcriptional interface between light stress and Fe stress responses. Through transcriptomics comparisons, we show that the changes in gene expression seen in ilr3 and pye show similarity to those seen when plants are stressed by high light (HL).
We next investigated whether ILR3 had a broader role to play in mitigating ROS-induced damage to PSII under various abiotic stresses. Through this study, we have established that ILR3 is involved in tolerance to HL, heat and cadmium (Cd) toxicity, all stresses, that similar to Fe deficiency, damage PSII. Furthermore, all these stresses require de-stacking of thylakoid membranes to initiate PSII repair. Importantly, our results also revealed ILR3 is required for the phosphorylation of D1, which is vital for grana de-stacking and essential for efficient PSII repair. Overall, this work expanded our knowledge of how plants regulate Fe deficiency and its cross talk with other abiotic stress pathways to protect the photosynthetic apparatus from photooxidative stress.
Riaz, Nabila, "How plants cope with stress" (2023). Dartmouth College Ph.D Dissertations. 171.
Available for download on Thursday, August 14, 2025