About this Research Topic
The so-called pigments of life, namely heme and chlorophylls, are synthesized through a well-conserved eight-step enzymatic pathway in eukaryotic cells. This pathway is not only essential for the autotrophic life of photosynthetic organisms, it is also tightly regulated. On the one hand, tetrapyrrole biosynthesis and breakdown generate some of the most toxic compounds (porphyrins) for cellular metabolism. Indeed, porphyrins including heme in their free form are a potential harmful source of oxidative stress. On the other hand, heme and some of its degradation products are required in the cell to mitigate oxidative stress. Heme is the prosthetic group of reactive oxygen species (ROS) scavenging enzymes such as catalases and peroxidases, whereas chlorophylls are central pigments for light energy trapping in photosynthesis. Hence, the homeostasis of porphyrin biosynthesis in plants is even more important during suboptimal environmental conditions, when the redox balance in the cell can result in signaling, damage, or death.
Recent evidence suggests that plant cells do regulate their tetrapyrrole biosynthetic pathway when encountering biotic or abiotic stresses. For instance, drought stress can be signaled through tetrapyrrole-dependent ROS accumulation. Chlorophyll biosynthesis is fine-tuned in response to changing light environments and chloroplast functionality. Some plant pathogenic bacteria rely on their host heme pool for their metabolism. In addition, defined enzymatic steps within the tetrapyrrole biosynthetic pathway are amenable to genetic or biochemical manipulation aiming at increasing tolerance to biotic and abiotic stresses, including herbicide resistance.
This Research Topic aims to present a comprehensive collection of current knowledge linking the regulation of tetrapyrrole biosynthesis and metabolism during biotic and abiotic stresses to the cellular redox status. Original research or review articles showing how tetrapyrrole biosynthesis is fine-regulated during biotic and abiotic stresses and how defined tetrapyrroles may be involved directly or indirectly in preventing or repairing ROS damage are welcomed. Furthermore, we encourage submissions dealing broadly with the specifics of how tetrapyrrole-dependent redox changes within organelles, defined cells, or organs could allow the plant to cope with its changing environment.
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