About this Research Topic
Photoreceptors sense and perceive light and, therefore, allow plants to regulate their physiological responses in harmony with the ever-changing environment. Each of these light-perceiving molecules are specialized to monitor a certain range of wavelengths. Phytochromes perceive the components of natural sunlight, red (λmax ~660 nm) and far-red (λmax ~730nm) light, and were discovered more than 50 years ago. It became evident that phytochromes mediate a wide range of responses but despite the large sets of data available, our knowledge on the fine details of phytochrome structure, evolution, function, and signaling is still rudimentary.
Phytochromes absorb light via the covalently attached linear tetrapyrrole chromophore. The chromophore allows the functional phytochrome holoprotein to operate as a light quality and quantity regulated switch by changing its conformation between the biologically active and inactive states depending upon irradiation conditions. As biochemical methods for structural analysis improve, researchers are obtaining more detailed structural information about phytochromes and are starting to decipher how light-induced conformational changes occur. Independent of this, it is well documented that light-induced conformational changes facilitate phytochrome-protein interactions, which are essential for proper signaling. We still need, however, to better understand at mechanistic level how light sensing by phytochromes is transduced into signaling to regulate morphological and developmental changes.
Phytochromes have been mainly examined in the widely used Arabidopsis thaliana model plant. These photoreceptors have also been identified in various plant taxa but little is known about their function in plants besides Arabidopsis. It is also noticed that in mosses, lycopods, ferns, and seed plants, similar to Arabidopsis, gene duplications led to the formation of phytochrome families, consisting of members with different functional properties. This diversity might have been important following the water-to-land transition of plants to adapt to a wide range of terrestrial habitats. Yet, we know very little about the underlying structural factors or signaling mechanisms of phytochromes in early-diverging land plants.
Based on the above aspects in this Research Topic we invite Original Research, Reviews, and other articles, on the following issues:
• Phytochrome structure and the process of photoconversion.
• Chromophore that provide light sensitivity to phytochromes.
• Phytochrome dynamics and regulation in cells: for example, proteostasis, nuclear import, photobody formation, etc.
• Phytochrome family members and their relation to each other in Arabidopsis.
• Phytochrome diversity and function in other plant species than Arabidopsis.
• Evolutionary aspects of phytochrome structure, function, and signaling.
• Posttranslational modification of phytochromes.
• Interaction of phytochromes with signaling partners and functionality of the signal transduction pathways.
Keywords: Phytochrome, Light signaling, Photoconversion
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