Defective kernel 66 encodes a GTPase essential for kernel development in maize.

Mitochondria is a semi-autonomous organelle that provides energy for cell activities through oxidative phosphorylation. In this study, we identified a defective kernel 66 (dek66)-mutant maize with defective kernels. We characterized the candidate gene DEK66, encoding a ribosomal assembly factor, locating in mitochondria, and possessing GTPase activity (the GTPase belonged to ribosome biogenesis GTPase A family). In the dek66 mutant, abolishment of mitochondrial structure and function led to the accumulation of reactive oxygen species and promoted programmed cell death in endosperm cells. Furthermore, transcript level of most of the key genes associated with nutrient storage, mitochondrial respiratory chain complex, and mitochondrial ribosomes in the dek66 mutant were significantly altered. Collectively, the results suggested that DEK66 is essential for the development of maize kernels via affecting the mitochondrial function. This study provided a reference to understand the impact of mitochondrial ribosomal assembly factor in maize kernel development.