Biology subjects

Askani, J.

Publications and source records attributed to Askani, J..

2 recordsLinked to original sources

bioRxiv2021

Light at the end of the tunnel: FRAP assay reveals that plant vacuoles start as a tubular network

Plant vacuoles play key roles in cellular homeostasis performing catabolic and storage functions, regulating pH and ion balance. The essential role of vacuoles for plant cell viability makes them a notoriously difficult subject to study impeding reaching the consensus on the mechanism of vacuolar establishment and the source of membrane material for it. Our previous suggestion of endoplasmic reticulum being the main membrane contributor for the tubular network of young vacuoles was recently challenged in a study proposing that young plant vacuoles comprise a set of individual vesicles that are formed de novo via homotypic fusion of multivesicular bodies (MVBs). To resolve these seemingly contradictory observations we have carefully revaluated both hypotheses. Here we provide a systematic overview of successive vacuolar biogenesis stages in Arabidopsis root, 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 organelles morphology and provide 3D models of vacuoles at all developmental stages. Furthermore, we established a customized FRAP assay and proved that even at the earliest stages of biogenesis, vacuoles comprise a connected network. Finally, we summarized the new and pre-existing evidence substantiating that vacuolar structures cannot originate solely from MVBs.

plant biology↗

bioRxiv2020

The Arabidopsis V-ATPase is localized to the TGN/EE via a seed plant specific motif and acts in a partially redundant manner with the tonoplast enzyme

Vacuolar-type H+-ATPases (V-ATPases) are versatile proton pumps that control the pH of many intracellular compartments in all eukaryotic cells. The localization of the Arabidopsis V-ATPase was previously shown to be determined by the isoforms of subunit a (VHA-a). The incorporation of VHA-a1 targets the V-ATPase to the trans-Golgi network/early endosome (TGN/EE) whilst the incorporation of VHA-a2 or VHA-a3 targets the V-ATPase to the tonoplast. By employing chimeric proteins and site directed mutagenesis we identified a targeting domain (a1-TD) containing an acidic cluster in the N-terminus of VHA-a1 that serves as both an ER export signal and as a TGN retention motif. The a1-TD is conserved among seed plants and we confirmed experimentally that its presence is predictive of TGN/EE- localization. In contrast to many other non-seed plants, the liverwort Marchantia polymorpha encodes only a single VHA-a subunit (MpVHA-a) and we show here that it is predominantly localized at the tonoplast. In our attempts to determine if MpVHA-a can functionally replace the Arabidopsis VHA-a isoforms, we used CRISPR/Cas9 to generate null-alleles lacking VHA-a1 and discovered that its function is essential for male gametophyte development but can be replaced by VHA-a2 and VHA-a3 during vegetative growth.Competing Interest StatementThe authors have declared no competing interest.View Full Text

plant biology↗