The endoplasmic reticulum membrane-bending protein RETICULON facilitates chloroplast relocation movement in Marchantia polymorpha.

Kazuya Ishikawa, Ryota Konno, Satoyuki Hirano, Yuta Fujii, Masayuki Fujiwara, Yoichiro Fukao, Yutaka Kodama

The Plant journal : for cell and molecular biology 2022 Jul

filter terms:

Plant cells alter the intracellular positions of chloroplasts to ensure efficient photosynthesis, a process controlled by the blue light receptor phototropin. Chloroplasts migrate toward weak light (accumulation response) and move away from excess light (avoidance response). Chloroplasts are encircled by the endoplasmic reticulum (ER), which forms a complex network throughout the cytoplasm. To ensure rapid chloroplast relocation, the ER must alter its structure in conjunction with chloroplast relocation movement, but little is known about the underlying mechanism. Here, we searched for interactors of phototropin in the liverwort Marchantia polymorpha and identified a RETICULON (RTN) family protein; RTN proteins play central roles in ER tubule formation and ER network maintenance by stabilizing the curvature of ER membranes in eukaryotic cells. Marchantia polymorpha RTN1 (MpRTN1) is localized to ER tubules and the rims of ER sheets, which is consistent with the localization of RTNs in other plants and heterotrophs. The Mprtn1 mutant showed an increased ER tubule diameter, pointing to a role for MpRTN1 in ER membrane constriction. Furthermore, Mprtn1 showed a delayed chloroplast avoidance response but a normal chloroplast accumulation response. The live cell imaging of ER dynamics revealed that ER restructuring was impaired in Mprtn1 during the chloroplast avoidance response. These results suggest that during the chloroplast avoidance response, MpRTN1 restructures the ER network and facilitates chloroplast movement via an interaction with phototropin. Our findings provide evidence that plant cells respond to fluctuating environmental conditions by controlling the movements of multiple organelles in a synchronized manner. © 2022 Society for Experimental Biology and John Wiley & Sons Ltd.

Citation

Kazuya Ishikawa, Ryota Konno, Satoyuki Hirano, Yuta Fujii, Masayuki Fujiwara, Yoichiro Fukao, Yutaka Kodama. The endoplasmic reticulum membrane-bending protein RETICULON facilitates chloroplast relocation movement in Marchantia polymorpha. The Plant journal : for cell and molecular biology. 2022 Jul;111(1):205-216