| Structural highlights
Function
CHUP1_ARATH Required for the positioning and movement of chloroplasts. Interacts with profilin and actin independent of its polymerization status. Regulates chloroplast localization by anchoring chloroplasts to the plasma membrane and forming a bridge to the actin cytoskeleton.[1] [2] [3] [4]
Publication Abstract from PubMed
Plants have unique responses to fluctuating light conditions. One such response involves chloroplast photorelocation movement, which optimizes photosynthesis under weak light by the accumulation of chloroplasts along the periclinal side of the cell, which prevents photodamage under strong light by avoiding chloroplast positioning toward the anticlinal side of the cell. This light-responsive chloroplast movement relies on the reorganization of chloroplast actin (cp-actin) filaments. Previous studies have suggested that CHLOROPLAST UNUSUAL POSITIONING 1 (CHUP1) is essential for chloroplast photorelocation movement as a regulator of cp-actin filaments. In this study, we conducted comprehensive analyses to understand CHUP1 function. Functional, fluorescently-tagged CHUP1 colocalized with and was coordinately reorganized with cp-actin filaments on the chloroplast outer envelope during chloroplast movement in Arabidopsis thaliana. CHUP1 distribution was reversibly regulated in a blue light- and phototropin-dependent manner. X-ray crystallography revealed that the CHUP1 C-terminal domain shares structural homology with the formin homology 2 (FH2) domain, despite lacking sequence similarity. Furthermore, the CHUP1 C-terminal domain promoted actin polymerization in the presence of profilin in vitro. Taken together, our findings indicate that CHUP1 is a plant-specific actin polymerization factor that has convergently evolved to assemble cp-actin filaments and enables chloroplast photorelocation movement.
CHLOROPLAST UNUSUAL POSITIONING 1 is a plant-specific actin polymerization factor regulating chloroplast movement.,Kong SG, Yamazaki Y, Shimada A, T Kijima S, Hirose K, Katoh K, Ahn J, Song HG, Han JW, Higa T, Takano A, Nakamura Y, Suetsugu N, Kohda D, Uyeda TQP, Wada M Plant Cell. 2023 Dec 22:koad320. doi: 10.1093/plcell/koad320. PMID:38134410[5]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Kasahara M, Kagawa T, Oikawa K, Suetsugu N, Miyao M, Wada M. Chloroplast avoidance movement reduces photodamage in plants. Nature. 2002 Dec 19-26;420(6917):829-32. PMID:12490952 doi:10.1038/nature01213
- ↑ Oikawa K, Kasahara M, Kiyosue T, Kagawa T, Suetsugu N, Takahashi F, Kanegae T, Niwa Y, Kadota A, Wada M. Chloroplast unusual positioning1 is essential for proper chloroplast positioning. Plant Cell. 2003 Dec;15(12):2805-15. PMID:14615600 doi:10.1105/tpc.016428
- ↑ Schmidt von Braun S, Schleiff E. The chloroplast outer membrane protein CHUP1 interacts with actin and profilin. Planta. 2008 Apr;227(5):1151-9. PMID:18193273 doi:10.1007/s00425-007-0688-7
- ↑ Oikawa K, Yamasato A, Kong SG, Kasahara M, Nakai M, Takahashi F, Ogura Y, Kagawa T, Wada M. Chloroplast outer envelope protein CHUP1 is essential for chloroplast anchorage to the plasma membrane and chloroplast movement. Plant Physiol. 2008 Oct;148(2):829-42. PMID:18715957 doi:10.1104/pp.108.123075
- ↑ Kong SG, Yamazaki Y, Shimada A, T Kijima S, Hirose K, Katoh K, Ahn J, Song HG, Han JW, Higa T, Takano A, Nakamura Y, Suetsugu N, Kohda D, Uyeda TQP, Wada M. CHLOROPLAST UNUSUAL POSITIONING 1 is a plant-specific actin polymerization factor regulating chloroplast movement. Plant Cell. 2023 Dec 22:koad320. PMID:38134410 doi:10.1093/plcell/koad320
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