Banana (Musa acuminata) fruits ripening at 30 °C or above fail to develop yellow peels; this phenomenon, called green ripening, greatly reduces their marketability. The regulatory mechanism underpinning high temperature-induced green ripening remains unknown. Here we decoded a transcriptional and post-translational regulatory module that causes green ripening in banana. Banana fruits ripening at 30 °C showed greatly reduced expression of 5 chlorophyll catabolic genes (CCGs), MaNYC1 (NONYELLOW COLORING 1), MaPPH (PHEOPHYTINASE), MaTIC55 (TRANSLOCON AT THE INNER ENVELOPE MEMBRANE OF CHLOROPLASTS 55), MaSGR1 (STAY-GREEN 1), and MaSGR2 (STAY-GREEN 2), compared to those ripening at 20 °C. We identified a MYB transcription factor, MaMYB60, that activated the expression of all 5 CCGs by directly binding to their promoters during banana ripening at 20 °C, while showing a weaker activation at 30 °C. At high temperatures, MaMYB60 was degraded. We discovered a RING-type E3 ligase MaBAH1 (benzoic acid hypersensitive 1) that ubiquitinated MaMYB60 during green ripening and targeted it for proteasomal degradation. MaBAH1 thus facilitated MaMYB60 degradation and attenuated MaMYB60-induced transactivation of CCGs and chlorophyll degradation. By contrast, MaMYB60 upregulation increased CCG expression, accelerated chlorophyll degradation, and mitigated green ripening. Collectively, our findings unravel a dynamic, temperature-responsive MaBAH1–MaMYB60–CCG module that regulates chlorophyll catabolism, and the molecular mechanism underpinning green ripening in banana. This study also advances our understanding of plant responses to high-temperature stress.

Guavas are typical tropical fruit with high nutritional and commercial value. Because of their thin skin and high metabolic rate, guavas are highly susceptible to water loss, physical damage, and spoilage, severely limiting their shelf-life. Guavas can typically only be stored for approximately one week at room temperature, making transportation, storage, and handling difficult, resulting in low profit margins in the industry. This review focuses on the physiological and biochemical changes and their molecular mechanisms which occur in postharvest guavas, and summarizes the various management strategies for extending the shelf-life of these sensitive fruits by means of physical and chemical preservation and their combinations. This review also suggests future directions and reference ideas for the development of safe and efficient shelf-life extension techniques.

Banana (Musa acuminata) fruit ripening under high temperatures (>24°C) undergoes green ripening due to failure of chlorophyll degradation, which greatly reduces marketability. However, the mechanism underlying high temperature-repressed chlorophyll catabolism in banana fruit is not yet well understood. Here, using quantitative proteomic analysis, 375 differentially expressed proteins were identified in normal yellow and green ripening in banana. Among these, one of the key enzymes involved in chlorophyll degradation, NON-YELLOW COLORING 1 (MaNYC1), exhibited reduced protein levels when banana fruit ripened under high temperature. Transient overexpression of MaNYC1 in banana peels resulted in chlorophyll degradation under high temperature, which weakens the green ripening phenotype. Importantly, high temperature induced MaNYC1 protein degradation via the proteasome pathway. A banana RING E3 ligase, NYC1 interacting protein 1 (MaNIP1), was found to interact with and ubiquitinate MaNYC1, leading to its proteasomal degradation. Furthermore, transient overexpression of MaNIP1 attenuated MaNYC1-induced chlorophyll degradation in banana fruits, indicating that MaNIP1 negatively regulates chlorophyll catabolism by affecting MaNYC1 degradation. Taken together, the findings establish a post-translational regulatory module of MaNIP1–MaNYC1 that mediates high temperature-induced green ripening in bananas.

The hormone ethylene is crucial in the regulation of ripening in climacteric fruit, such as bananas. The transcriptional regulation of ethylene biosynthesis throughout banana fruit ripening has received much study, but the cascaded transcriptional machinery of upstream transcriptional regulators implicated in the ethylene biosynthesis pathway is still poorly understood. Here we report that ethylene biosynthesis genes, including MaACS1, MaACO1, MaACO4, MaACO5, and MaACO8, were upregulated in ripening bananas. NAC (NAM, ATAF, CUC) transcription factor, MaNAC083, a ripening and ethylene-inhibited gene, was discovered as a potential binding protein to the MaACS1 promoter by yeast one-hybrid screening. Further in vitro and in vivo experiments indicated that MaNAC083 bound directly to promoters of the five ethylene biosynthesis genes, thereby transcriptionally repressing their expression, which was further verified by transient overexpression experiments, where ethylene production was inhibited through MaNAC083-modulated transcriptional repression of ethylene biosynthesis genes in banana fruits. Strikingly, MaMADS1, a ripening-induced MADS (MCM1, AGAMOUS, DEFICIENS, SRF4) transcription factor, was found to directly repress the expression of MaNAC083, inhibiting trans-repression of MaNAC083 to ethylene biosynthesis genes, thereby attenuating MaNAC083-repressed ethylene production in bananas. These findings collectively illustrated the mechanistic basis of a MaMADS1–MaNAC083–MaACS1/MaACOs regulatory cascade controlling ethylene biosynthesis during banana fruit ripening. These findings increase our knowledge of the transcriptional regulatory mechanisms of ethylene biosynthesis at the transcriptional level and are expected to help develop molecular approaches to control ripening and improve fruit storability.