title: Chloroplast biogenesis during rehydration of the resurrection plant Xerophyta humilis: parallels to the etioplast-chloroplast transition.
abstract: De-etiolation of dark-grown seedlings is a commonly used experimental system to study the mechanisms of chloroplast biogenesis, including the stacking of thylakoid membranes into grana, the response of the nuclear-chloroplast transcriptome to light, and the ordered synthesis and assembly of photosystem II (PSII). Here, we present the xeroplast to chloroplast transition during rehydration of the resurrection plant Xerophyta humilis as a novel system for studying chloroplast biogenesis, and investigate the role of light in this process. Xeroplasts are characterized by the presence of numerous large and small membrane-bound vesicles and the complete absence of thylakoid membranes. While the initial assembly of stromal thylakoid membranes occurs independently of light, the formation of grana is light dependent. Recovery of photosynthetic activity is rapid in plants rehydrated in the light and correlates with the light-dependent synthesis of the D1 protein, but does not require de novo chlorophyll biosynthesis. Light-dependent synthesis of the chlorophyll-binding protein Lhcb2 and digalactosyldiacylglycerol synthase 1 correlated with the formation of grana and with the increased PSII activity. Our results suggest that the molecular mechanisms underlying photomorphogenic development may also function in desiccation tolerance in poikilochlorophyllous resurrection plants.
authors.affiliation: Department of Molecular and Cell Biology, University of Cape Town, Private Bag, Rondebosch 7701, South Africa.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Ingle
authors.forename: Helen
authors.initials: H
authors.lastname: Collett
authors.forename: Keren
authors.initials: K
authors.lastname: Cooper
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Takahashi
authors.forename: Jill M
authors.initials: JM
authors.lastname: Farrant
authors.forename: Nicola
authors.initials: N
authors.lastname: Illing
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism; D002734:Chlorophyll / Q000032:analysis; D002736:Chloroplasts / Q000378:metabolism* / Q000648:ultrastructure; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D008027:Light; D019684:Magnoliopsida / Q000235:genetics / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D018749:RNA, Plant / Q000235:genetics; D014867:Water
chemical_list: D045332:Photosystem II Protein Complex; D018749:RNA, Plant; D014867:Water; D002734:Chlorophyll; D002245:Carbon Dioxide