title: Defective etioplasts observed in variegation mutants may reveal the light-independent regulation of white/yellow sectors of Arabidopsis leaves.
abstract: Leaf variegation resulting from nuclear gene mutations has been used as a model system to elucidate the molecular mechanisms of chloroplast development. Since most variegation genes also function in photosynthesis, it remains unknown whether their roles in photosynthesis and chloroplast development are distinct. Here, using the variegation mutant thylakoid formation1 (thf1) we show that variegation formation is light independent. It was found that slow and uneven chloroplast development in thf1 can be attributed to defects in etioplast development in darkness. Ultrastructural analysis showed the coexistence of plastids with or without prolamellar bodies (PLB) in cells of thf1, but not of WT. Although THF1 mutation leads to significant decreases in the levels of Pchlide and Pchllide oxidoreductase (POR) expression, genetic and 5-aminolevulinic acid (ALA)-feeding analysis did not reveal Pchlide or POR to be critical factors for etioplast formation in thf1. Northern blot analysis showed that plastid gene expression is dramatically reduced in thf1 compared with that in WT, particularly in the dark. Our results also indicate that chlorophyll biosynthesis and expression of plastidic genes are coordinately suppressed in thf1. Based on these results, we propose a model to explain leaf variegation formation from the plastid development perspective.
authors: National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, the Chinese Academy of Sciences, Shanghai 200032, China.
authors: Wenjuan
authors: W
authors: Wu
authors: Nabil
authors: N
authors: Elsheery
authors: Qing
authors: Q
authors: Wei
authors: Lingang
authors: L
authors: Zhang
authors: Jirong
authors: J
authors: Huang
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D015152:Blotting, Northern; D002736:Chloroplasts / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000528:radiation effects; D008027:Light; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000235:genetics / Q000378:metabolism; D018515:Plant Leaves / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D018087:Plastids / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D008565:Membrane Proteins; C512069:THF1 protein, Arabidopsis; D010088:Oxidoreductases; D044925:Oxidoreductases Acting on CH-CH Group Donors; C023886:protochlorophyllide reductase