Defective Etioplasts Observed in Variegation Mutants May Reveal the Light-Independent Regulation of White/Yellow Sectors of Arabidopsis Leaves  

作　　者：Wenjuan Wu Nabil Elsheery Qing Wei Lingang Zhang Jirong Huang 

机构地区：[1]National Key Laboratory of Plant Molecular Genetics, Institute of Plant-PhysTology and-Ecology, Shanghai Institutesfor Biological Sciences, the Chinese Academy of Sciences, Shanghai 200032, China [2]present address： Division of Nephrology and Hypertension, Mayo Clinic, Rochester, MN 55905, USA [3]Present address： Institute of Plant Science and Resources, okayama University, Kurashiki, Okayama, Japan

出　　处：《Journal of Integrative Plant Biology》2011年第11期846-857,共12页植物学报（英文版）

基　　金：supported by the Ministry of Science and Technology of China (2007CB108800 and 2009CB118504 to J. H.);Science and Technology Commission of Shanghai Municipality (09ZR1436300 to L. Z.);National Special Grantfor Transgenic Crops (2009ZX08009-081B to J. H.)

摘　　要：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 （thfl） we show that variegation formation is light independent. It was found that slow and uneven chloroplast development in thfl 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 thfl, but not of WT. Although THF1 mutation leads to significant decreases in the levels of Pchlide and Pchliide 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 thfl. Northern blot analysis showed that plastid gene expression is dramatically reduced in thfl 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 thfl. Based on these results, we propose a model to explain leaf variegation formation from the plastid development perspective.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 （thfl） we show that variegation formation is light independent. It was found that slow and uneven chloroplast development in thfl 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 thfl, but not of WT. Although THF1 mutation leads to significant decreases in the levels of Pchlide and Pchliide 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 thfl. Northern blot analysis showed that plastid gene expression is dramatically reduced in thfl 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 thfl. Based on these results, we propose a model to explain leaf variegation formation from the plastid development perspective.

关 键 词：ARABIDOPSIS CHLOROPLAST ETIOPLAST THF1/Psb29 VARIEGATION Pchllide oxidoreductase Pchlide oxidoreductase chloroplastdevelopment. 

分 类 号：Q943[生物学—植物学] S511[农业科学—作物学]