Plasma membrane-anchored chloroplasts are necessary for the gravisensing system of Ceratopteris richardii prothalli
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The prothalli of the fern Ceratopteris richardii exhibit negative gravitropism when grown in darkness. However, no sedimentable organelles or substances have been detected in the prothallial cells, suggesting that a non-sedimentable gravisensor exists. We investigated whether chloroplasts are involved in the gravisensing system of C. richardii prothalli. We used a clumped-chloroplast mutant, clumped chloroplast 1 (cp1), in which the chloroplasts are detached from the plasma membrane and clustered around the nucleus likely because of a partial deletion in the KINESIN-LIKE PROTEIN FOR ACTIN-BASED CHLOROPLAST MOVEMENT 1 gene. The cp1 mutation resulted in prothalli that had a significantly diminished gravitropic response, while the phototropic response occurred normally. These results suggest that plasma membrane-anchored chloroplasts in prothallial cells function as one of the gravisensors in C. richardii prothalli.
KeywordsCeratopteris richardii Fern gametophyte Gravitropism Gravity perception
This work was supported by JSPS KAKENHI Grant Number JP15K11914.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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