Fruit Ripening and Senescence Regulated by Ethylene and Melatonin
Pengfei Zhao, Yuxing Zhang, Haixia Zhang*
Hebei Agricultural University, Baoding, China
Submission: June 18, 2021; Published: June 18, 2021
*Corresponding author: Haixia Zhang, College of Horticulture, Hebei Agricultural University, China
How to cite this article: Pengfei Z, Yuxing Z, Haixia Z. Fruit Ripening and Senescence Regulated by Ethylene and Melatonin. Agri Res & Tech: Open Access J. 2021; 26 (1): 556324. DOI: 10.19080/ARTOAJ.2021.25.556324
Abstract
Fruit ripening and senescence are two important stages of fruit development, during which many physiological and biochemical changes going on. Hormones play critical roles in fruit ripening and senescence, and among them, ethylene is the most outstanding one. It could promote climacteric and non-climacteric fruit ripening and senescence and the regulating mechanisms have been much clearer. Melatonin is an bioactive substance existing in nearly all kinds of pants and it is involved in most growth and development processes of plant. Recent researches showed that melatonin can promote fruit ripening by increasing ethylene production, pigment and aroma/taste, and decreasing cell wall sickness et al. While it can inhibit fruit senescence by eliminating excessive reactive oxygen species (ROS). However, the specific regulating mechanism is still not clear, and further studies are urgently needed.
Keywords: Fruit; Ripening; Senescence; Ethylene; Melatonin; Regulating mechanism
Introduction
Fruit ripening and senescence
After pollination and fertilization, the fruit forms and it will generally experience fruit setting, fruit development, fruit maturity and fruit senescence under natural conditions. Among them, fruit maturity and senescence are the last two stages. The ripening process is irreversible and during which the synthesis and degradation of substances take place simultaneously [1]. And senescence comes after the fruit mature changes are basically over. The content of soluble solids increased and the ratio of sugar to acid increased during fruit ripening. Sugar transporters are the main carriers of sucrose from the source tissues to the fruit tissues and they play a leading role in the accumulation of fructose. In addition to the transport and metabolism of sucrose in fruit, starch degradation is another important mechanism of sugar accumulation. Starch is mainly accumulated in the developing fruit and hydrolyzed to soluble sugar during ripening by amylase activity [2]. Changes in cell wall structure include decrease of cell wall thickness and permeability of plasma membrane, hydration of cell wall, decrease in structural integrity, and increase in intracellular space [3]. The change of fruit texture is an important event in the softening process during fruit ripening and it is strictly regulated. The activities of enzymes that catalyze cell wall decoposition were greatly enhanced during fruit ripening, which is consistent with the changes of the transcription level of genes encoding them [4-6].
Regulation of ethylene on fruit ripening and senescence
Ethylene, as a plant hormone, functions in many aspects of plant growth and development, and it is typically known as a regulator during fruit ripening. According to whether there are ethylene release peak and respiration peak during fruit ripening, fruits are divided into climacteric fruits and non-climacteric fruits. The climacteric fruit had enhanced respiration and changed metabolism at maturity, and released a large amount of ethylene, while non-climacteric fruits have no respiratory climacteric during ripening. Early studies suggest that ethylene is only related to fruit ripening, but recently more and more researchers believe that ethylene also plays a role in non-climacteric fruit ripening [7]. And its regulating mechanism is relatively clear [8].
Regulation of melatonin on fruit ripening and senescence
Melatonin is a bioactive small molecule substances widely existing in animals and plants and it was first discovered in plants in 1995 [9]. Researches have shown that melatonin plays an important role in anti-oxidation, resistance to abiotic stresses, and delaying senescence by scavenging ROS [10]. Although fruit ripening and senescence is hard to be distinguished, melatonin has a positive regulatory effect on fruit ripening, while has an inhibitory effect on fruit senescence [11-13].
Conclusion
So far, the mechanisms of ethylene regulating fruit ripening and senescence have been relatively clear. As to melatonin, on the one hand, it can promote fruit ripening, and on the other hand, it can delay fruit senescence. Therefore, it may be a balance mechanism. However, the specific regulatory mechanism is unclear, and it is necessary to be further studied. In addition, it is very interesting to carry out research on if ethylene and melatonin have synergism or antagonism on fruit ripening and senescence.
Acknowledgements
Thanks for the financial support of Special Fund for Talent Introduction of Hebei Agricultural University (YJ201960, KY201902).
Conflict of Interest
There is no conflict of interest exists.
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