Fsd2, or Fibronectin Type III and SPRY Domain Containing 2, has diverse functions across different organisms. In plants, it is a chloroplast-localized iron superoxide dismutase (FeSOD), involved in protecting against reactive oxygen species (ROS) and crucial for chloroplast development and stress responses [1,2,5,6]. In mammals, it is associated with the stability of excitation-contraction coupling protein complexes in muscle tissues [3,4].

In Arabidopsis, loss-of-function mutants of Fsd2 show increased superoxide production, reduced chlorophyll levels, and lower photosynthetic efficiency, indicating its essential role in photosynthetic processes [1]. In rice, the cyclophilin OsCYP20-2 promotes OsFsd2 to form homodimers, enhancing its activity to eliminate ROS under chilling stress [7]. In mice, Speg-deficient models show abnormal myospryn complex with decreased Fsd2 levels, leading to defective triad formation and abnormal muscle function [4].

In summary, Fsd2 is vital for maintaining cellular homeostasis in plants and muscle function in mammals. Studies using gene-knockout models in plants and mice have revealed its roles in photosynthesis, stress responses, and muscle-related biological processes, providing insights into potential mechanisms underlying plant adaptation and muscle-associated diseases.

References:

1. Gallie, Daniel R, Chen, Zhong. 2019. Chloroplast-localized iron superoxide dismutases FSD2 and FSD3 are functionally distinct in Arabidopsis. In PloS one, 14, e0220078. doi:10.1371/journal.pone.0220078. https://pubmed.ncbi.nlm.nih.gov/31329637/

2. Bychkov, Ivan A, Andreeva, Aleksandra A, Kudryakova, Natalia V, Pojidaeva, Elena S, Kusnetsov, Victor V. 2022. The role of PAP4/FSD3 and PAP9/FSD2 in heat stress responses of chloroplast genes. In Plant science : an international journal of experimental plant biology, 322, 111359. doi:10.1016/j.plantsci.2022.111359. https://pubmed.ncbi.nlm.nih.gov/35738478/

3. Lee, Chang Seok, Jung, Sung Yun, Yee, Rachel Sue Zhen, Rodney, George G, Hamilton, Susan L. 2023. Speg interactions that regulate the stability of excitation-contraction coupling protein complexes in triads and dyads. In Communications biology, 6, 942. doi:10.1038/s42003-023-05330-y. https://pubmed.ncbi.nlm.nih.gov/37709832/

4. Li, Qifei, Lin, Jasmine, Luo, Shiyu, Perrella, Mark A, Agrawal, Pankaj B. 2024. Integrated multi-omics approach reveals the role of striated muscle preferentially expressed protein kinase in skeletal muscle including its relationship with myospryn complex. In Journal of cachexia, sarcopenia and muscle, 15, 1003-1015. doi:10.1002/jcsm.13470. https://pubmed.ncbi.nlm.nih.gov/38725372/

5. Garcia-Molina, Antoni, Altmann, Melina, Alkofer, Angela, Dangl, Jeffery L, Falter-Braun, Pascal. . LSU network hubs integrate abiotic and biotic stress responses via interaction with the superoxide dismutase FSD2. In Journal of experimental botany, 68, 1185-1197. doi:10.1093/jxb/erw498. https://pubmed.ncbi.nlm.nih.gov/28207043/

6. Myouga, Fumiyoshi, Hosoda, Chieko, Umezawa, Taishi, Ikeuchi, Masahiko, Shinozaki, Kazuo. 2008. A heterocomplex of iron superoxide dismutases defends chloroplast nucleoids against oxidative stress and is essential for chloroplast development in Arabidopsis. In The Plant cell, 20, 3148-62. doi:10.1105/tpc.108.061341. https://pubmed.ncbi.nlm.nih.gov/18996978/

7. Ge, Qiang, Zhang, Yuanyuan, Xu, Yunyuan, Qian, Qian, Chong, Kang. 2019. Cyclophilin OsCYP20-2 with a novel variant integrates defense and cell elongation for chilling response in rice. In The New phytologist, 225, 2453-2467. doi:10.1111/nph.16324. https://pubmed.ncbi.nlm.nih.gov/31736073/