Arabidopsis light-dependent protochlorophyllide oxidoreductase A (PORA) is essential for normal plant growth and development

Abstract

During skotomorphogenesis in angiosperms, NADPH:protochlorophyllide oxidoreductase (POR) forms an aggregate of photolabile NADPH-POR-protochlorophyllide (Pchlide) ternary complexes localized to the prolamellar bodies within etioplasts. During photomorphogenesis, POR catalyzes the light-dependent reduction of Pchlide a to chlorophyllide (Chlide) a, which is subsequently converted to chlorophyll (Chl). In Arabidopsis there are three structurally related POR genes, denoted PORA, PORB and PORC. The PORA and PORB proteins accumulate during skotomorphogenesis. During illumination, PORA is only transiently expressed, whereas PORB and PORC persist and are responsible for bulk Chl synthesis throughout plant development. Here we have tested whether PORA is important for skotomorphogenesis by assisting in etioplast development, and normal photomorphogenic development. Using reverse genetic approaches, we have identified the porA-1 null mutant, which contains an insertion of the maize Dissociation transposable element in the PORA gene. Additionally, we have characterized PORA RNAi lines. The porA-1 and PORA RNAi lines display severe photoautotrophic growth defects, which can be partially rescued on sucrose-supplemented growth media. Elimination of PORA during skotomorphogenesis results in reductions in the volume and frequency of prolamellar bodies, and in photoactive Pchlide conversion. The porA-1 mutant characterization thus establishes a quantitative requirement for PORA in etioplast development by demonstrating significant membrane ultrastructural and biochemical defects, in addition to suggesting PORA-specific functions in photomorphogenesis and plant development.

Two NADPH: Protochlorophyllide Oxidoreductase (POR) Isoforms Play Distinct Roles in Environmental Adaptation in Rice

“…In angiosperms, during skotomorphogenesis in the dark, PORs combine with NADPH and Pchlide to produce a ternary complex that makes up the main protein component of the prolamellar body (PLB) in the etioplast (Schoefs and Franck 2003; Paddock et al 2012). The PLB, which has a lattice-like structure, also contains Chl precursors, carotenoids, and lipids (Rosinski and Rosen 1972; Selstam and Sandelius 1984).…”

Cloning and functional characterization of PjPORB, a member of the POR gene family in Pseudosasa japonica cv. Akebonosuji

“…And, an increasing number of por mutants have been characterized in Arabidopsis to elucidate the roles of the three AtPOR isoforms in detail. For example, the porA mutant displays stunted chlorina phenotype and photoautotrophic growth defect, and hence provides direct evidence to support an essential role for AtPORA in normal plant growth and development (Paddock et al 2012); the porB and porC mutants do not exhibit any phenotypic changes at the whole plant or chloroplast ultrastructural levels. Nevertheless, the porB porC double mutant displays a severe xantha (highly chlorophyll-deficient) phenotype and is characterized by smaller prolamellar bodies in etioplasts and decreased thylakoid stacking in chloroplasts, thus providing good evidence for the redundant roles for AtPORB and AtPORC in maintaining light-dependent Chl biosynthesis in green plants (Frick et al 2003;Masuda and Takamiya 2004).…”

“…It is well known that the insertion or deletion in POR gene results in chlorine (Paddock et al 2012), severe xanthan (Frick et al 2003), or yellow/white variegation leaf phenotype in por mutants (Sakuraba et al 2013); and more severely, the simultaneous silencing of all the POR genes leads to an albino phenotype in POR-RNAi tobacco plants (Talaat 2013). Since the PjPORB identified in this study was found to have an intact gene structure and play a full function in Pchlide photoreduction, it is tempting to study whether there is link between PjPORB expression and the unique leaf color variation in P. japonica cv.…”

“…Akebonosuji, and overexpressed it in Arabidopsis to study its function in Chl biosynthesis. Given the red leaf phenotype observed in POR-repressed A. tricolor (Iwamoto et al 2001), the albino phenotype in POR-silenced tobacco plants (Talaat 2013), and other abnormal leaf phenotypes observed in por mutants, like the chlorina phenotype in Arabidopsis porA mutant (Paddock et al 2012), the severe xantha phenotype in Arabidopsis porB porC double mutant (Frick et al 2003), and the yellow/white variegation in rice fgl (porB) mutant (Sakuraba et al 2013), it is intriguing to investigate the link between the POR gene expression and leaf color variation in P. japonica cv. Akebonosuji.…”

The hot, the cold and the tulip : the regulation of flowering time and dormancy release

“…In addition, the PORA gene was selected to be confirmed by qRT-PCR. This gene is important for skotomorphogenesis and normal photomorphogenic development (Paddock et al, 2012). Differently from LHCB2.2 and PSBW, the expression of PORA increased from week 12 onwards (Fig.…”