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NADK2, an Arabidopsis chloroplastic NAD kinase, plays a vital role in both chlorophyll synthesis and chloroplast protection.
- Source :
-
Plant molecular biology [Plant Mol Biol] 2005 Nov; Vol. 59 (4), pp. 553-64. - Publication Year :
- 2005
-
Abstract
- As one of terminal electron acceptors in photosynthetic electron transport chain, NADP receives electron and H(+) to synthesize NADPH, an important reducing energy in chlorophyll synthesis and Calvin cycle. NAD kinase (NADK), the catalyzing enzyme for the de novo synthesis of NADP from substrates NAD and ATP, may play an important role in the synthesis of NADPH. NADK activity has been observed in different sub-cellular fractions of mitochondria, chloroplast, and cytoplasm. Recently, two distinct NADK isoforms (NADK1 and NADK2) have been identified in Arabidopsis. However, the physiological roles of NADKs remain unclear. In present study, we investigated the physiological role of Arabidiposis NADK2. Sub-cellular localization of the NADK2-GFP fusion protein indicated that the NADK2 protein was localized in the chloroplast. The NADK2 knock out mutant (nadk2) showed obvious growth inhibition and smaller rosette leaves with a pale yellow color. Parallel to the reduced chlorophyll content, the expression levels of two POR genes, encoding key enzymes in chlorophyll synthesis, were down regulated in the nadk2 plants. The nadk2 plants also displayed hypersensitivity to environmental stresses provoking oxidative stress, such as UVB, drought, heat shock and salinity. These results suggest that NADK2 may be a chloroplast NAD kinase and play a vital role in chlorophyll synthesis and chloroplast protection against oxidative damage.
- Subjects :
- Amino Acid Sequence
Arabidopsis cytology
Arabidopsis genetics
Chlorophyll biosynthesis
Chlorophyll genetics
Gene Expression Regulation, Enzymologic
Gene Expression Regulation, Plant
Hot Temperature
Molecular Sequence Data
NADP metabolism
Phenotype
Phosphotransferases (Alcohol Group Acceptor) genetics
Plant Transpiration
Sequence Alignment
Sequence Homology, Amino Acid
Sodium Chloride
Ultraviolet Rays
Arabidopsis enzymology
Chlorophyll metabolism
Chloroplasts physiology
Phosphotransferases (Alcohol Group Acceptor) metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 0167-4412
- Volume :
- 59
- Issue :
- 4
- Database :
- MEDLINE
- Journal :
- Plant molecular biology
- Publication Type :
- Academic Journal
- Accession number :
- 16244906
- Full Text :
- https://doi.org/10.1007/s11103-005-6802-y