Musa acuminata calmodulin-binding transcription activator 4 enhances fruit quality maintenance of banana during cold storage.

In this study, we identified a calmodulin-binding transcription activator (CAMTA), designated as MaCAMTA4, and then investigated into its functions in banana fruit during storage at low temperature (6 °C). Transient overexpression of MaCAMTA4 markedly alleviated chilling injury (CI) symptoms whereas silencing of MaCAMTA4 exhibited more severe CI symptoms, while overexpression of MaCAMTA4 reduced the contents of H₂O₂, superoxide anion and malondialdehyde, enhanced the activities of antioxidant enzymes, and limited the polyphenol oxidase activity during storage at 6 °C. MaCAMTA4 overexpression maintained mitochondrial integrity and promoted autophagy by observation from transmission electron microscopy (TEM). Targeted metabolomic analysis demonstrated further that MaCAMTA4 reprogrammed metabolic profiles during storage at 6 °C, as characterized by accumulations of nucleotides, amino acids, carbohydrates and enhanced adenosine triphosphate (ATP) content, along with significant enrichments of pentose phosphate pathway and carbon metabolism. Collectively, these results indicated that MaCAMTA4 acted as a positive regulator of chilling tolerance by coordinating reactive oxygen species (ROS) scavenging, cellular structural maintenance and central energy metabolism in banana fruit during storage at 6 °C.