Ultrastructure of the Periplastidial Compartment of the Diatom Phaeodactylum tricornutum

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• 作者：Serena Flori^a ; Pierre-Henri Jouneau^b ; Giovanni Finazzi^a ; Eric Maré ; chal^a ; ¹ ; ^{eric.marechal@cea.fr" class="auth_mail" title="E-mail the corresponding author} ; Denis Falconet^a
• 关键词：Phaeodactylum ; diatoms ; secondary plastids ; secondary endosymbiosis ; periplastidial compartment ; SELMA.
• 刊名：Protist
• 出版年：2016
• 出版时间：June 2016
• 年：2016
• 卷：167
• 期：3
• 页码：254-267
• 全文大小：9812 K

文摘

Diatoms contain a secondary plastid that derives from a red algal symbiont. This organelle is limited by four membranes. The two outermost membranes are the chloroplast endoplasmic reticulum membrane (cERM), which is continuous with the host outer nuclear envelope, and the periplastidial membrane (PPM). The two innermost membranes correspond to the outer and inner envelope membranes (oEM and iEM) of the symbiont's chloroplast. Between the PPM and oEM lies a minimized symbiont cytoplasm, the periplastidial compartment (PPC). In Phaeodactylum tricornutum, PPC-resident proteins are localized in “blob-like-structures”, which remain associated with plastids after cell disruption. We analyzed disrupted Phaeodactylum cells by focused ion beam scanning electron microscopy, revealing the presence of a vesicular network (VN) in the PPC, at a location consistent with blob-like structures. Presence of a VN in the PPC was confirmed in intact cells. Additionally, direct membrane contacts were observed between the PPM and nuclear inner envelope membrane at the level of the chloroplast-nucleus isthmus. This study provides insights into the PPC ultrastructure and opens perspectives on the function of this residual cytoplasm of red algal origin.