OsNDUFA9 encoding a mitochondrial complex I subunit is essential for embryo development and starch synthesis in rice

Abstract

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.

FLOURY ENDOSPERM19 encoding a class I glutamine amidotransferase affects grain quality in rice

“…Rice endosperm is known to be an excellent system for elucidating how gene networks regulate starch synthesis and amyloplast development (Nelson and Pan 2003;Satoh and Omura 1981), so various mutants with defective endosperm have been screened for further research. In terms of appearance, oury endosperm mutants can generally be divided into two types: completely oury endosperm mutant (such as FLO13 (Hu et al 2018), FLO14 (Xue et al 2019), FLO16 (Teng et al 2019) and FLO18 (Yu et al 2020)) and partially oury endosperm mutant (such as FLO4 (Kang et al 2005), FLO7 and FLO15 (You et al 2019)). Interestingly, similar to previously reported o7 mutant, the peripheral region of o19 mutant grain also appeared oury-white (Fig.…”

Genetic and Molecular Factors Determining Grain Weight in Rice

“…FLO10 encodes a pentatricopeptide repeat protein that acts as a chaperone in the trans -splicing of mitochondrial nad1 intron 1 during endosperm development ( Wu et al, 2019 ). It has also been shown that a mitochondrial complex I subunit (FLO13) controls grain size, grain quality and thousand grain weight and is associated with the respiratory electron chain complex of the mitochondria ( Hu T. et al, 2018 ). A class I glutamine amidotransferase named FLO19, has been reported to affect grain quality and the expression of other amyloses ( Lou et al, 2021 ).…”

Genetic Control and High Temperature Effects on Starch Biosynthesis and Grain Quality in Rice

“…FLO13, known as OsNDUFA9, encodes subunit mitochondrial complex I. Loss of OsNDUFA9 changes the mitochondrial structure and greatly impairs the development of rice endosperm (Hu et al, 2018). FLO16, known as OsCMDH, encodes an NAD-dependent cytosolic malate dehydrogenase.…”