In the bustling mitochondrial factory, a new ability of the mitochondrial gene cytochrome b (CYTB) brothers has been unlocked by Chinese scientists. On May 3, the international journal Cell Metabolism published the research results of Liu Xingguo's research group of the Chinese Academy of Sciences Guangzhou Institute of Biomedicine and Health. They discovered and confirmed for the first time that the mitochondrial gene cytochrome b can encode a new mitochondrial gene that encodes the cytoplasmic translation protein CYTB-187AA, further indicating that CYTB-187AA plays an important role in early mammalian development. This study rewrote the assertion in textbooks that the mitochondrial genome encodes 13 proteins. In cells, there are numerous organelles, such as different workshops, that carry out life activities in an orderly manner, maintaining the operation of the entire cell. Among them, mitochondria are a special type of organelle that has its own DNA, known as the mitochondrial genome. "The nucleus stores the important genome of the human body. The genome is transcribed and translated, gradually constructing the main components of our individual, which is our most fundamental life material. The mitochondrial genome is also transcribed and translated." The corresponding author of the paper, Liu Xingguo, introduced, "Mitochondria are very small, and the mitochondrial genome they contain is also small, only containing 37 genes. These genes each play their own roles, and 13 of them can encode proteins." Can the coding region of the mitochondrial genome use the cytoplasmic standard genetic code to encode new proteins? "? The research team selected the mitochondrial coding gene CYTB, which is the only respiratory chain complex III. They found that in addition to encoding cytochrome b in mitochondria, CYTB can also use cytoplasmic codons to encode a new mitochondrial genome encoding the cytoplasmic translation protein CYTB-187AA. This protein is localized to mitochondria and regulates energy production to participate in early developmental processes by interacting with SLC25A3 protein. To verify the origin of its mitochondrial genome, the research team compared mitochondrial genome deficient cells with wild-type cells and found that CYTB-187AA was only expressed in the latter. "We found in the knockdown mouse model that a decrease in CYTB-187AA reduces the number of follicles, thereby impairing female fertility," said Liu Xingguo. Previously, the possibility of using cytoplasmic ribosomes to translate mRNA encoded by 13 mitochondrial genes into new proteins has not been explored. This study rewrote the assertion in textbooks that the mitochondrial genome encodes 13 proteins and found that the CYTB gene can use the standard genetic code of cytoplasmic ribosomes to encode the 14th novel protein. "The English abbreviation PACT for this model has the meaning of 'agreement', so this new model is called 'mitochondrial agreement'. Liu Xingguo said that this study revealed that CYTB-187AA is localized in the mitochondrial matrix after cytoplasmic translation, and regulates early development through the energy common currency 'adenosine triphosphate' dependence, playing an important role in early mammalian development.". (Lai Xin She)