10:45 AM - 12:15 PM
[BPT04-P06] Does the phosphorus acquisition mechanism of photosynthetic organisms co-evolve with the global phosphorus environment?
Keywords:Phosphate, Phosphate transporter
It is estimated that for 80-90% of the Earth's 4.5 billion year history, phosphorus was buried in nearshore sediments in the form of orthophosphate (PO43-) due to the influence of iron-rich seas (Bjerrum and Canfield, 2002). Thus, Pi concentrations during the Neogene to Proterozoic (3.2 to 1.9 billion years) are thought to have been 10 to 25% of those of today. On the other hand, it is also believed that dissolved silica was abundant in the oceans at that time, and some believe that silica was not limited to iron as the phosphates available to organisms to bind iron particles (Konhauser et al., 2007). Subsequently, with the increase of phosphates in sediments 540 million years ago, a marked change in oxygen and diversification of organisms (Johnston et al., 2009, Reinhard et al. , 2017), suggesting that phosphorus on Earth was the rate-limiting factor for life development.
The current phosphorus environment on Earth varies. In the oceans, for example, phosphorus is present below the sea surface at average concentrations of 0.1-0.4 μM, but phosphorus is more abundant in the polar regions, with "hot" spots of concentrations exceeding 2 μM observed on the Antarctic continent. These concentrations also increase with depth (1.2-3.2 μM at 1000 m depth). On land, analyses of 5275 soils from around the world show differences ranging from 1.4 to 9630 mg kg-1 (He et al. , 2021). Soils from natural ecosystems without fertilizer additions have much lower phosphorus content (average 26,8 to 62,2 mg kg-1). Most of the phosphate present in the soil is either bound to organic matter or is a cation (Fe, Al, Ca, Cd...) ) or inorganic forms chelated by clays, for example in the range of 0,032 µM to 310 µM of phosphate available to plants. Therefore, organisms have evolved with a variety of phosphate uptake systems to recover phosphate from the environment. We hypothesized that the diversity and evolution of these systems may reflect the phosphorus transition in the global environment. In this study, we focused on phosphorus transporter proteins, comparing their sequences and using the recently developed protein structure prediction software AlphaFold 2 (Jumper et al. , 2021; Skolnick et al. , 2021), we classified phosphotransporter proteins into four distinct groups. Among them are high-affinity and low-affinity transporters that are used to fine-tune phosphorus absorption. This difference in function is assigned to different proteins in bacteria and yeast, while in plants, post-translational regulation is thought to modulate activity from high-affinity to low-affinity depending on phosphorus supply (Ayadi et al. , 2015). The highest affinity transporters are those corresponding to the lowest concentrations of phosphorus in unicellular organisms. The Km of yeast and bacteria is 0,1-0,5 μM, and some phytoplanktonic organisms have the ability to survive in phosphorus environments of only 10-20 nM. This indicates that bacteria from the terrestrial early life have a mechanism that responds to low concentrations, whereas higher plants are able to respond to high concentrations. In the poster, we will present data that support the low-phosphorus theory of early Earth from an evolutionary biological viewpoint.
The current phosphorus environment on Earth varies. In the oceans, for example, phosphorus is present below the sea surface at average concentrations of 0.1-0.4 μM, but phosphorus is more abundant in the polar regions, with "hot" spots of concentrations exceeding 2 μM observed on the Antarctic continent. These concentrations also increase with depth (1.2-3.2 μM at 1000 m depth). On land, analyses of 5275 soils from around the world show differences ranging from 1.4 to 9630 mg kg-1 (He et al. , 2021). Soils from natural ecosystems without fertilizer additions have much lower phosphorus content (average 26,8 to 62,2 mg kg-1). Most of the phosphate present in the soil is either bound to organic matter or is a cation (Fe, Al, Ca, Cd...) ) or inorganic forms chelated by clays, for example in the range of 0,032 µM to 310 µM of phosphate available to plants. Therefore, organisms have evolved with a variety of phosphate uptake systems to recover phosphate from the environment. We hypothesized that the diversity and evolution of these systems may reflect the phosphorus transition in the global environment. In this study, we focused on phosphorus transporter proteins, comparing their sequences and using the recently developed protein structure prediction software AlphaFold 2 (Jumper et al. , 2021; Skolnick et al. , 2021), we classified phosphotransporter proteins into four distinct groups. Among them are high-affinity and low-affinity transporters that are used to fine-tune phosphorus absorption. This difference in function is assigned to different proteins in bacteria and yeast, while in plants, post-translational regulation is thought to modulate activity from high-affinity to low-affinity depending on phosphorus supply (Ayadi et al. , 2015). The highest affinity transporters are those corresponding to the lowest concentrations of phosphorus in unicellular organisms. The Km of yeast and bacteria is 0,1-0,5 μM, and some phytoplanktonic organisms have the ability to survive in phosphorus environments of only 10-20 nM. This indicates that bacteria from the terrestrial early life have a mechanism that responds to low concentrations, whereas higher plants are able to respond to high concentrations. In the poster, we will present data that support the low-phosphorus theory of early Earth from an evolutionary biological viewpoint.