Phytochromes in rice are encoded by a gene family composed of three members, PHYA, PHYB, and PHYC. Through characterizing the phytochrome mutants and wild type （WT） in terms of photomorphogenesis, roles of individua...Phytochromes in rice are encoded by a gene family composed of three members, PHYA, PHYB, and PHYC. Through characterizing the phytochrome mutants and wild type （WT） in terms of photomorphogenesis, roles of individual phytochromes have been preliminarily explored in regulating rice de-etiolation, flowering time and fertility. However, little information has been reported about whether or how phytochromes affect chlorophyll biosynthesis and chloroplast development in rice. In this study, we compared the chlorophyll contents of wild type and the phyA, phyB and phyAphyB mutants grown under either white light （WL） or red light （R）. The results suggest that phyB perceives R to positively regulate chlorophyll biosynthesis, while the role of phyA can be detected only in the phyB-deficient mutant. Analyses of the expression levels of genes involved in chlorophyll biosynthesis revealed that phytochromes affected the chlorophyll biosynthesis by regulating protochlorophyll oxidoreductase A （PORA） expression. The role of phyB in chloroplast development was also analyzed, and the results suggest that phyB perceives R to regulate chloroplast development by affecting the numbers of chloroplasts and grana, as well as the chloroplast membrane system.展开更多
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...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.展开更多
基金supported by the grants from the National Natural Science Foundations of China(Grant Nos.30870192 and 30971744)the National Major Science and Technology Project to Create New Crop Varieties Using Gene Transfer Technology,China(Grant No.2009ZX08001-029B)the Shandong Natural Science Funds for Distinguished Young Scholar,China(Grant No.JQ200911)
文摘Phytochromes in rice are encoded by a gene family composed of three members, PHYA, PHYB, and PHYC. Through characterizing the phytochrome mutants and wild type （WT） in terms of photomorphogenesis, roles of individual phytochromes have been preliminarily explored in regulating rice de-etiolation, flowering time and fertility. However, little information has been reported about whether or how phytochromes affect chlorophyll biosynthesis and chloroplast development in rice. In this study, we compared the chlorophyll contents of wild type and the phyA, phyB and phyAphyB mutants grown under either white light （WL） or red light （R）. The results suggest that phyB perceives R to positively regulate chlorophyll biosynthesis, while the role of phyA can be detected only in the phyB-deficient mutant. Analyses of the expression levels of genes involved in chlorophyll biosynthesis revealed that phytochromes affected the chlorophyll biosynthesis by regulating protochlorophyll oxidoreductase A （PORA） expression. The role of phyB in chloroplast development was also analyzed, and the results suggest that phyB perceives R to regulate chloroplast development by affecting the numbers of chloroplasts and grana, as well as the chloroplast membrane system.
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.)
文摘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.
