OsNDUFA9 encoding a mitochondrial complex I subunit is essential for embryo development and starch synthesis in rice
Loss of function of a mitochondrial complex I subunit (OsNDUFA9) causes abnormal embryo development and affects starch synthesis by altering the expression of starch synthesis-related genes and proteins.
Proton-pumping NADH: ubiquinone oxidoreductase (also called complex I) is thought to be the largest and most complicated enzyme of the mitochondrial respiratory chain. Mutations of complex I subunits have been revealed to link with a number of growth inhibitions in plants. However, the function of complex I subunits in rice remains unclear. Here, we isolated a rice floury endosperm mutant (named flo13) that was embryonic lethal and failed to germinate. Semi-thin sectioning analysis showed that compound starch grain development in the mutant was greatly impaired, leading to significantly compromised starch biosynthesis and decreased 1000-grain weight relative to the wild type. Map-based cloning revealed that FLO13 encodes an accessory subunit of complex I protein (designated as OsNDUFA9). A single nucleotide substitution (G18A) occurred in the first exon of OsNDUFA9, introducing a premature stop codon in the flo13 mutant gene. OsNDUFA9 was ubiquitously expressed in various tissues and the OsNDUFA9 protein was localized to the mitochondria. Quantitative RT-PCR and protein blotting indicated loss of function of OsNDUFA9 altered gene expression and protein accumulation associated with respiratory electron chain complex in the mitochondria. Moreover, transmission electron microscopic analysis showed that the mutant lacked obvious mitochondrial cristae structure in the mitochondria of endosperm cell. Our results demonstrate that the OsNDUFA9 subunit of complex I is essential for embryo development and starch synthesis in rice endosperm.
KeywordsOsNDUFA9 Mitochondrial complex I subunit Embryo development Starch synthesis Rice (Oryza sativa L.)
Days after flowering
Derived cleaved amplified polymorphic sequence
Ethyl methane sulfonate
Electron transfer chain
Green fluorescent protein
NADH dehydrogenase subunit
Mitochondrial NADH dehydrogenase [ubiquinone] 1 alpha subcomplex subunit 9
Open reading frame
Scanning electron microscope
Transmission electron microscope
This research was supported by the Key Laboratory of Biology, Genetics and Breeding of Japonica Rice in Mid-lower Yangtze River, Ministry of Agriculture of China, The Yangtze River Valley Hybrid Rice Collaboration Innovation Center, Jiangsu Collaborative Innovation Center for Modern Crop Production, and the grants from The National Key Research and Development Program of China (2017YFD0100400), a project (2016ZX08001006) from the Ministry of Agriculture of China for transgenic research, Jiangsu Science and Technology Development Program (BE2015355-1), and Jiangsu Province Self-Innovation Program [CX(16)1029]. This work was also supported by the Fundamental Research Funds for the Central Universities (KYTZ201601).
Compliance with ethical standards
Conflict of interest
These authors declare that they have no conflict of interest.
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