PT  - JOURNAL ARTICLE
AU  - Diede de Haan
AU  - Hadas Peled-Zehavi
AU  - Yoseph Addadi
AU  - Oz Ben Joseph
AU  - Lior Aram
AU  - Assaf Gal
TI  - Exocytosis of the silicified cell wall of diatoms involves extensive membrane disintegration
AID  - 10.1101/2021.09.14.460270
DP  - 2021 Jan 01
TA  - bioRxiv
PG  - 2021.09.14.460270
4099  - http://biorxiv.org/content/early/2021/09/14/2021.09.14.460270.short
4100  - http://biorxiv.org/content/early/2021/09/14/2021.09.14.460270.full
AB  - Diatoms are unicellular algae that are characterized by their silica cell walls. The silica elements form intracellularly in a membrane-bound organelle, and are exocytosed after completion. How diatoms maintain membrane homeostasis during the exocytosis of these large and rigid silica elements is a long-standing enigma. We studied membrane dynamics during cell wall formation and exocytosis in the diatom Stephanopyxis turris, using live-cell confocal microscopy and advanced electron microscopy. Our results provide detailed information on the ultrastructure and dynamics of the silicification process, showing that during cell wall formation, the organelle membranes tightly enclose the mineral phase, creating a precise mold of the delicate geometrical patterns. Surprisingly, during exocytosis of the mature silica elements, the proximal organelle membrane becomes the new plasma membrane, and the distal membranes gradually disintegrate into the extracellular space without any noticeable endocytic retrieval or extracellular repurposing. These observations suggest that diatoms evolved an extraordinary exocytosis mechanism in order to secrete their cell wall elements.Competing Interest StatementThe authors have declared no competing interest.