Abstract
Plant vacuoles play key roles in cellular homeostasis performing catabolic and storage functions, regulating pH and ion balance1,2. The essential role of vacuoles for plant cell viability makes them a notoriously difficult subject to study. As a consequence, there is still no consensus on the mechanism of vacuolar establishment and the source of membrane material for it. Our previous suggestion of endoplasmic reticulum (ER) being the main contributor of membrane for growing young vacuoles3 was recently challenged in a study proposing that plant vacuoles are formed de novo via homotypic fusion of multivesicular bodies (MVBs)4. Authors of this work pointed out issues that might explain our seemingly contradictory observations and we have thus carefully revaluated our hypothesis.
Using the Arabidopsis thaliana root as a model, we provide a systematic overview of successive vacuolar biogenesis stages, starting from the youngest cells proximate to the quiescent center. We validate our previous conclusions by demonstrating that the vacuolar dye BCECF is fully suitable for studying the organelle morphology and provide 3D models from vacuoles of all developmental stages. We established a customized FRAP assay and proved that even at the earliest stages of biogenesis, vacuoles comprise a connected network. Together, this adds to a growing body of evidence indicating that vacuolar structures cannot originate solely from MVBs.
Competing Interest Statement
The authors have declared no competing interest.
Abbreviations
- CLSM
- confocal laser scanning microscopy
- CTPP
- C-terminal propeptide
- BCECF
- BCECF-AM, 2′,7′-Bis-(2-Carboxyethyl)-5-(and-6)-Carboxyfluorescein, Acetoxymethyl Ester
- DZ
- differentiation zone
- ER
- endoplasmic reticulum
- EZ
- elongation zone
- FRAP
- fluorescence recovery after photobleaching
- ILVs
- intraluminal vesicles
- MVBs
- multi vesicular bodies
- MZ
- meristematic zone
- NTPP
- N-terminal propeptide
- QC
- quiescent center
- SVs
- small vacuoles
- TEM
- transmission electron microscopy