Recently, Horticulture Research published a research paper by Professor Li Xueping’s research group from the Key Laboratory of Fruit and Vegetable Preservation, South China Agricultural University titled “The interaction of CpEBF1 with CpMADSs is involved in cell wall degradation during papaya fruit ripening.” This study reveals the possible molecular mechanism of ripening disorder in papaya caused by inappropriate post-harvest 1-MCP treatment, providing a theoretical basis for maintaining the quality of post-harvest papaya and offering new ideas and foundations for preserving other fruits that experience ripening disorders due to environmental factors or improper post-harvest treatments.
Figure 1. The effects of 1-MCP on the cell wall structure of papaya during ripening (A,B) and the effects on cellulose and lignin content (C)
Papaya (Carica papaya L.) is highly nutritious and beneficial for health, known as the “king of beneficial fruits.” It is a typical climacteric tropical fruit that must undergo ripening after harvest to reach its unique optimal flavor. However, papaya fruit is not storage-tolerant, and it quickly matures, ages, and deteriorates in quality during post-harvest circulation, resulting in significant losses. 1-Methylcyclopropene (1-MCP) treatment can significantly delay the ripening and aging of various fruits during post-harvest storage and transportation, but in practical applications, it is challenging to grasp the appropriate concentration of 1-MCP. Too high a concentration or inappropriate harvest maturity can lead to ripening disorders in papaya (commonly known as “rubber ripe”), making it difficult for the flesh to soften normally even after ethylene ripening treatment, severely affecting the edible quality and market value, thus limiting the application of 1-MCP in papaya preservation. The mechanisms causing ripening disorders in papaya are currently unclear.
This study employed two different 1-MCP treatment methods on papaya fruit. A short duration of 1-MCP treatment can delay papaya fruit ripening and allow for normal ripening, while a prolonged 1-MCP treatment inhibits fruit ripening and causes “rubber ripe” fruit. Cell wall structure analysis found that 1-MCP treatment can better maintain cell wall structure and delay cell wall degradation, thus delaying fruit ripening. In contrast, prolonged 1-MCP treatment keeps the cell wall structure of the fruit in its initial state throughout the storage period, while increasing cellulose and lignin content in the cell wall. Inappropriate 1-MCP treatment also significantly inhibited the expression of key genes related to cell wall degradation and the activity of cell wall degrading enzymes. At the same time, gene expression analysis revealed that prolonged 1-MCP significantly inhibited the expression of the key gene in the ethylene signaling pathway, CpEBF1, indicating that it may play an important role in the fruit ripening process. Yeast two-hybrid, BiFC, and GST pull-down experiments identified the interacting proteins of CpEBF1: CpMADS1/ 3 and CpEIL1. Subcellular localization showed that these interacting proteins are located in the nucleus. The interaction between CpEBF1 and CpMADS1 / 3 can activate the activity of the promoters of key genes involved in cell wall degradation. However, inappropriate 1-MCP treatment significantly inhibits the expression of CpEBF1 and CpMADS1 / 3, leading to the failure of key genes and enzymes responsible for cell wall degradation, ultimately resulting in the inability of the fruit to soften and ripen normally.
This study preliminarily reveals the mechanism of ripening disorder in papaya fruit caused by improper 1-MCP treatment, thus providing a theoretical basis and new ideas for the application of papaya fruit preservation technology. Additionally, too high a concentration of 1-MCP or inappropriate harvest maturity can lead to ripening disorders in kiwi, banana, mango, apple, and other fruits, affecting fruit flavor. The research results are also of significant theoretical importance in revealing the ripening mechanisms of other fruits with ripening disorders.
Figure 2. Possible mechanism diagram of the softening effect of 1-MCP treatment on papaya fruit
The first authors of this paper are Dr. Ding Xiaochun and Associate Professor Zhu Xiaoyang from the College of Horticulture, South China Agricultural University, with Professor Li Xueping and Professor Chen Weixin as corresponding authors. This research was funded by the National Natural Science Foundation. Professors Chen Weixin and Li Xueping’s team has long been engaged in the research and development of preservation technology for tropical and subtropical fruits and vegetables (such as bananas, papayas, lychees, etc.) and the related mechanisms of quality formation, receiving various awards including the second prize of National Science and Technology Progress and the first prize of Guangdong Province Science and Technology Progress, and has published dozens of SCI papers.
Horticulture Research Introduction
Horticulture Research is an English journal co-founded by Nanjing Agricultural University and the Nature Publishing Group (now Springer Nature). It is the first journal in the field of horticulture under Nature and is currently the only Chinese SCI journal in the horticultural field. All basic and theoretical research on horticultural crops can be submitted. Horticulture Research has an impact factor of 3.368 in 2018, ranking 2nd out of 37 in horticulture (2/37); 31st out of 222 in plant science (31/222). It is the only Chinese SCI journal in the field of horticulture. The impact factor of the journal in the Chinese Academy of Sciences classification in 2018 is 3.368, with a 3-year average impact factor of 3.961, ranking 2nd out of 35 in horticulture (2/35); 21st out of 222 in plant science (21/222), and is recognized as a TOP journal in the category of agricultural and forestry sciences. It is the only Chinese SCI journal in the field of horticulture and agricultural and forestry science. Online submission address: Click here to enter. Learn more: Click here to learn more.
