On July 12, the rape team of Huazhong Agricultural University published a report entitled”Brassica napus bnantt1 modules ATP homeostasis in plastics to sustain me” in cell reports“Tabolism and growth”. This study clarified the function and molecular mechanism of transporter bnantt1 in regulating rape metabolism and growth.
The transporter that exchanges atp/adp between the endoplasmic body and cytoplasm of plant cells is nucleotide triphosphate transporter (NTT), which is responsible for transporting ATP from the cytoplasm into the plastid, exchanging the same amount of ADP, maintaining the dynamic balance of atp/adp in the plastid, and meeting ATP dependent metabolic activities such as fatty acid and amino acid synthesis in the plastid. There are few reports on whether NTT binds and transports cytoplasmic ATP into plastids in plants, and the molecular mechanism of NTT regulating plant growth and metabolism is unclear.
This study first confirmed that bnantt1 protein was located on the inner membrane of chloroplast. By expressing the protein in vitro, using nanodsf, SPR technology and separating rape leaf plastids to detect metabolites, it was proved that bnantt1 could bind ATP, transport cytoplasmic ATP into plastids, and exchange ADP into cytoplasm.
The results showed that mutant bnantt1 reduced the glycolysis efficiency in cytoplasm and the content of lipid metabolites such as DGDG, mgdg and PG in chloroplasts, resulting in thylakoid structural defects, reduced photosynthetic efficiency and led to slow growth of rape, and the oil content in seeds also decreased significantly. Overexpression of bnantt1 caused the increase of ATP content in plastids, ADP content in cytoplasm and adp/atp ratio in cytoplasm, which promoted the efficiency of glycolysis. The elevated ATP level in plastids may increase the activity of AGPase and promote the formation of starch. Increased ATP in seed plastids increased the rate of fatty acid synthesis, thereby promoting the accumulation of oil in seeds. This study revealed the biochemical and molecular mechanism of rape transporter bnantt1, which transports cytoplasmic ATP to plastids to maintain rape metabolism and growth and promote lipid synthesis, and provides a target gene for rape breeding with high yield and high oil content.
Xia Hui and Li Xiao, Ph.D. and postgraduates from the State Key Laboratory of crop genetic improvement, central China Agricultural University, are the co first authors of the paper, and Professor Guo Liang is the corresponding author of the paper. The research was supported by the National Natural Science Foundation of China and Hubei Hongshan laboratory.
The plastid-localized nucleotide triphosphate transporter （NTT） transports cytosolic adenosine triphosphate （ATP） into plastid to satisfy the needs of biochemistry activities in plastid. Here, we investigate the key functions of two conserved BnaNTT1 genes, BnaC06.NTT1b and BnaA07.NTT1a, in Brassica napus. Binding assays and metabolic analysis indicate that BnaNTT1 binds ATP/adenosine diphosphate （ADP）， transports cytosolic ATP into chloroplast, and exchanges ADP into cytoplasm. Thylakoid structures are abnormal and plant growth is retarded in CRISPR mutants of BnaC06.NTT1b and BnaA07.NTT1a. Both BnaC06.NTT1b and BnaA07.NTT1a play important roles in the regulation of ATP/ADP homeostasis in plastid. Manipulation of BnaC06.NTT1b and BnaA07.NTT1a causes significant changes in glycolysis and membrane lipid composition, suggesting that increased ATP in plastid fuels more seed-oil accumulation. Together, this study implicates the vital role of BnaC06.NTT1b and BnaA07.NTT1a in plant metabolism and growth in B. napus.
Paper link:https://www.cell.com/cell-reports/fulltext/S2211-1247 （22）00858-0