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The rice faded green leaf locus encodes protochlorophyllide oxidoreductase B and is essential for chlorophyll synthesis under high light conditions
Author(s) -
Sakuraba Yasuhito,
Rahman Md Lutfor,
Cho SungHwan,
Kim YeSol,
Koh HeeJong,
Yoo SooCheul,
Paek NamChon
Publication year - 2013
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12110
Subject(s) - protochlorophyllide , chlorophyll , biology , etiolation , mutant , oxidoreductase , botany , biochemistry , gene , enzyme
Summary NADPH :protochlorophyllide oxidoreductase ( POR ) catalyzes photoreduction of protochlorophyllide (Pchlide) to chlorophyllide in chlorophyll (Chl) synthesis, and is required for prolamellar body ( PLB ) formation in etioplasts. Rice faded green leaf ( fgl ) mutants develop yellow/white leaf variegation and necrotic lesions during leaf elongation in field‐grown plants. Map‐based cloning revealed that FGL encodes Os PORB , one of two rice POR isoforms. In fgl , etiolated seedlings contained smaller PLB s in etioplasts, and lower levels of total and photoactive Pchlide. Under constant or high light ( HL ) conditions, newly emerging green leaves rapidly turned yellow and formed lesions. Increased levels of non‐photoactive Pchlide, which acts as a photosensitizer, may cause reactive oxygen accumulation and lesion formation. Os PORA expression is repressed by light and Os PORB expression is regulated in a circadian rhythm in short‐day conditions. Os PORA was expressed at high levels in developing leaves and decreased dramatically in fully mature leaves, whereas Os PORB expression was relatively constant throughout leaf development, similar to expression patterns of At PORA and At PORB in Arabidopsis. However, Os PORB expression is rapidly upregulated by HL treatment, similar to the fluence rate‐dependent regulation of At PORC . This suggests that Os PORB function is equivalent to both At PORB and At PORC functions. Our results demonstrate that Os PORB is essential for maintaining light‐dependent Chl synthesis throughout leaf development, especially under HL conditions, whereas Os PORA mainly functions in the early stages of leaf development. Developmentally and physiologically distinct roles of monocot Os POR s are discussed by comparing with those of dicot At POR s .