Molecular basis and fitness implications of the interplay between light and the regulation of iron homeostasis in photosynthetic organisms

Abstract

Photosynthetic organisms respond to changes in the external environment, including responses to changes in light color, intensity and nutrient availability. Iron is one of the nutrients that is critical for the function of photosynthetic organisms, primarily due to the high demand for iron in the photosynthetic photosystems, electron transport chains of plastids and mitochondria, and the structural and functional roles for iron in many critical proteins. Given the connection between iron demands and light-dependent processes such as photosynthesis, as well as the interplay between light and iron, there is a need for finely tuned co-regulation of light and iron acclimation responses to optimize photosynthesis and minimize potential dangerous interactions between iron and light. Such regulation is critical for balancing light and nutrient availability in the coordination of light-dependent aspects of organismal fitness. To accomplish this regulation, there is molecular crosstalk and/or common effectors in light signaling and iron acclimation control. We explore known paradigms that are central to light-iron interactions and the associated regulation of fitness in photosynthetic organisms.

Changes in the Elemental and Metabolite Profile of Wheat Phloem Sap during Grain Filling Indicate a Dynamic between Plant Maturity and Time of Day

“…Ferritin production was found to be repressed by the expression of TIC under low Fe supply and in the presence of light and diurnal cycles [ 14 ]. Furthermore, links have been made between Fe and the regulation of circadian rhythms [ 18 ] and Fe homeostasis and light [ 19 ], with the Fe supply affecting the length of the circadian period [ 18 ] and a co-regulation between light and Fe acclimation responses [ 19 ]. Interactions between ferritin genes and light have also been observed in rice, with the presence of light stimulating the expression and production of ferritin in rice seedlings [ 20 ].…”

“…An important part of mineral translocation is the efficient transport of target micronutrients (i.e., Fe and Zn) from source to the sink (i.e., from soil, through to the roots, stems and leaves, and then to the seed) and therefore the long-distance vascular pathways play a significant role in delivering nutrients to seeds [ 21 ]. The effects of diurnal patterns observed in Fe homeostasis in various tissues of photosynthetic organisms [ 19 ] and more specifically the interaction between phytosiderophores and diurnal patterns in the roots of rice [ 11 ] point to the potential for changes in the phloem exudate nutrient concentration with the time of day.…”

The Tryptophan-Rich Sensory Protein (TSPO) is Involved in Stress-Related and Light-Dependent Processes in the Cyanobacterium Fremyella diplosiphon

“…Responses to light, availability of iron and other nutrients, tetrapyrrole metabolism, and oxidative stress are co-regulated. For example, iron uptake and transport are light-regulated in photosynthetic organisms, often linked to photoreceptors ( Montgomery et al, 2015 ). In F. diplosiphon the photoreceptor RcaE controls not only chromatic acclimation ( Kehoe and Grossman, 1996 ; Terauchi et al, 2004 ), but is also involved in acclimation to iron-deficiency ( Pattanaik et al, 2014 ).…”