Academician Sun Dawen, South China University of Technology: The role of plant hormones in fruit and vegetable storage and application

Original title: Sun Dawen, South China University of Technology: The Role of Plant Hormones in The Storage of Fruits and Vegetables
December 24, 2020,

, a member of the University of South China University of Technology, published an online review entitled "Phytohormones in postharvest storage of fruits and vegetables" at
Critical Reviews in Food Science and Nutrition
(IF - 7.862), which systematically describes the latest advances in the storage and preservation of plant hormones after fruit and vegetable harvesting. Sun Dawen of South China University of Technology is the only correspondent for this paper.
1,
fruits and vegetables contain a variety of vitamins, dietary fiber, carbohydrates and minerals, is an essential source of nutrition for the human diet. According to the Food and Agriculture Organization of the United Nations (FAO), the gap between food supply and demand is widening as populations grow, food is lost and wasted. The scientific community has also taken note of this critical situation and warned that bridging this gap is extremely urgent and important. Physical methods such as low-temperature storage are convenient and effective, but their effectiveness varies from product to product due to the complexity and diversity of fruits and vegetables. Chemical methods are simple and effective, but possible chemical residues are unacceptable to consumers. Biotechnology methods, such as enzyme technology and plant hormones, are non-toxic and safe. In particular, researchers have found that plant hormones can greatly prolong the storage period of fresh produce. Plant hormones can be produced by plants or synthesized, both of which can participate in plant physiological and bio-chemical reactions. Therefore, unlike conventional chemical methods that may produce chemical residues, plant hormone treatment has gradually developed into an important means of regulating the physiology of fresh fruits and vegetables after harvesting. A number of related reviews have been published in the past. Mahajan et al. (2014) summarized the characteristics of different post-harvest treatment methods for fresh produce based on physical, chemical, air conditioning and new treatment methods. Vo?et al. (2014) reviewed the modeling methods for different plant hormone transport and signaling. Wani et al. (2016) reviewed the roles, engineering techniques and cross-regulation of plant hormones in food crops under conditions such as cold, drought and high temperatures. However, the study on the mechanism and application of plant hormones to prolong the storage period after fruit and vegetable harvesting has not been reported. Therefore, Wenjuan Xiang, Hsiao-Wen Wang and Da-Wen Sun of the School of Food Science and Engineering of South China University of Technology focus on the effects of plant hormones on physiological changes after fruit and vegetable harvesting. The mechanism of these plant hormones is expounded from the aspects of activating the defense gene expression, inhibiting the sensitivity and expression of aging-related plant hormones, improving the activity of antioxidant enzymes, and maintaining the integrity of cell membranes, discusses the application of 6 common plant hormones in prolonging the storage period of fruits and vegetables, and emphasizes the challenges of plant hormone development as an effective post-harvest treatment method.
2, the regulatory mechanism of plant hormones
plant hormones are a group of signal molecules produced by plants. Even at very low concentrations, they have a significant effect on regulating metabolism. Although different definitions and criteria may affect the classification of plant hormones, jasmonates (JAs), salicylic acid (SA), cytocline (cytokinins, CTKs), and erythromycin (gibberellin) S, GAs), polyamines( PAs), rapeseed (brassinosteroids, BRs), shedding acid (abscisic acid, ABA) and ethylene (ethylene, ETH) are recognized as plant hormones. JAs are derived from fatty acids in cell membrane metabolism and consist of methyl jasmonate (MeJA) and free acid jasmine acid (JA). JAs play a variety of roles in plant growth, development and reproduction. It can also induce various defensive responses against pathogens and adverse environmental stresses. Therefore, ja mediation path is an important part of plant defense system. SA is a natural phenol and another important member of the plant defense system. As a widely available substance in plants, SA plays an important role in plant growth, development, maturation and coping with environmental stress. In addition, different concentrations of SA have diametrically opposed effects in plants. Low-concentration SA enhances the body's resistance to environmental stress, and high-concentration SA induces apoptosis. CTKs are a series of growth process regulators in plants. Studies have shown that CTK can promote cell division, bud differentiation, seed germination, leafy body formation, especially to delay aging. The U.S. Environmental Protection Agency (EPA) has confirmed that CTKs such as percitin and 6-penicillin (6-benzylaminopurine, 6-BA) are non-toxic plant growth regulators in agriculture. Therefore, CTK has been widely used in fruits and vegetables after harvesting preservation. GAs play a major role in regulating growth and development in plants. Because GAs have a erythromycin carbon skeleton and a seventh carbon atom carboxyl, seed germination and cell division can be activated. GAs can also produce antagonists associated with aging, such as ETH and ABA. As a result, GAs are widely used to extend the storage period after fruit and vegetable harvesting. PAs are a class of two or more amine-based substances that regulate the physiological and bio-chemical processes that are replicated from DNA to organ development and are resistant to environmental stress, including sperm, subcrystalline, or staphylactic. Therefore, PA has been applied to the post-harvest stage of fruits and vegetables to alleviate physiological disorders caused by abiothring stress. BRs are a class of steroids derived from methiciltic acid. Their biosynthetics are similar to CTK in that they have a similar effect on plant growth and environmental stress. Recent trials have also found that BRs treatment improves the fruit's tolerance to biological and abiothic stress. Finally, ABA and ETH are generally considered to be two plant hormones that regulate aging and maturity. In both aged and damaged fruits and vegetables, both levels increased. Therefore, proper control of the anabolic levels of these two plant hormones is of great significance to the preservation of fruits and vegetables. Although the above plant hormones are mainly involved in plant growth and development regulation, but they can also be through a variety of ways to regulate the physiological disorders and diseases after harvesting fruits and vegetables, and thus to maintain the quality of fruits and vegetables.
2.1
activated defense gene expression
disease decay, physiological disorders, mechanical damage and natural aging are important causes of post-harvest quality decline. The body defense system mainly deals with these biological and abscesses. These defensive reactions include insect resistance caused by JAs and disease resistance caused by SAs. JA and SA do not function entirely independently. They always intersect with other plant hormones. JAs play a critical role in defense systems. These compounds primarily trigger defensive responses by dissocenting the JA response gene from the JAZ, a family of proteins that act as a inhibitor of many transcription factors. Ja responds to gene transcription to produce plant antitoxins and protease inhibitors that enhance the body's tolerance to unpredictable environments. Studies of model plants such as amoeba and rice have revealed specific, adjustable and evolutionary signaling paths for JAs.
2.2
inhibits expression and
/
or sensitivity of aging-related plant hormones
fruits and vegetables age naturally after harvest. The regulation of aging by plant hormones has both promoting and inhibiting factors. ETH and ABA are promotors of accelerated aging, and CTK and GAs are inhibitors that can delay aging by inhibiting the biosynthetic and/or sensitivity of aging-related plant hormones. As a result, CTK or GAs can be used to extend the storage period of post-harvest agricultural products. CTK can be derived from bioactive derivatives N
6
-(
2
-isoprene-based) - Adenine (N
6
-(
2
-is opentenyl) - adenine, iP) and isoprene-based adenosine (isopentenyl adenosine, iPA) inhibit the production of ETH, and/or reduce ETH sensitivity through cytosensin reaction regulator factors (CRRs). However, the network of interrelations between CTK and ETH or other aging-related compounds has not been fully revealed, and only some possible regulatory signaling path pathfects are currently understood.
2.3
increases the activity of antioxidant enzymes
the induction of reactive oxygen (reactive oxygen species, ROS) and free fundamentals is enhanced during harvesting and storage. These excess metabolites shorten the storage period of fresh produce by oxidizing, destroying enzymes and breaking down cell membranes. Exogenetic plant hormones can be activated by activating antioxidant enzymes such as superoxide dismutase (SOD), hydrogen peroxide enzyme (catalase, CAT), peroxidase (peroxidase, POD), glutathione peroxymease (glutathione peroxyme) accumulation of idase, GSH-Px) or antioxidant products such as ascorbic acid (ascorbic acid AsA), β-carotene, and glutathione (GSH) to remove these oxidizing metabolites.
2.4
Maintaining the Integrity of Cytogenetic Membranes
Cytocytosomes are complex and essential tissues in plant cells, consisting of lipid bi-molecular layers and proteins, and are associated with many physiological processes and cell defense. The integrity of the membrane, including the integrity of the structure and function of the membrane, plays an important role in resisting biological and abstinical stress.
3. Application of plant hormones in fruit and vegetable storage
3.1
resistance to biological stress
Note: jasmonates, JAs), sali cylic acid, SA), cytokinins( CTKs), erythromycin (gibberellins, GAs), polyamines, PAs, brassinoster BRs), methyl jasmonate (methyl jasmonate, MeJA), methyl salicylate, MeSA), 6-peptide (6-benz) ylaminopurine, 6-BA, a CTK), benzodiagen (
N
-(2-chlorine-4-pyridine) -
N
'- phenylurea (
N
-(2-chloro-4-pyridil) -
N
'-phenylurea, CPPU, A synthetic CTK similar), 24-table canola (24-epibrassinolide, 24-EBR), nitroprusside(sodium nitroprusside, SNP, a Nitrogen oxide feeder), 1-aminocypropane-1-acetate-1 (1-aminocyclopropane-1-carboxylate synthase-1,
ACS1
), 1-aminocypropane-1-acetase-2 (1-aminocyclopropane-1-carboxylate synthase-2,
ACS2
),
ETR1
(ethylene response-1),
ERS1
(Ers1) (1), ascorbate peroxidase (APX), hydrogen peroxide enzyme (catalase, CAT), 1,1-diphenyl-2-DPP methylazyl (1-diphenyl-2-picrylhydrazyl, H), hydrogen peroxide (hydrogen peroxide, H
2
O
2
), acetaldehyde (malondialdehyde, MDA), phenylalanine ammonia, PAL), peroxidase (peroxidase, POD), polyphenol oxidase (polyphenol oxidase, PPO), Superoxide dismutase ( SOD), relative humidity (RH).
table 2 summarizes the positive effects of plant hormones on prolonging the storage period of fruits and vegetables. After treatment by JAs or SAS, fruits and vegetables not only have the ability to resist biological stress, but also observe high cold resistance. For example, Chen et al. (2019) demonstrated that exo-MeJA can relieve the cold damage of peach fruits, and Glowacz et al. (2017) showed that 100 smol/L MeJA and MeSA significantly reduced the cold damage of 'Hass' avocados. In addition, different plant hormones are often used together for better preservation. SAs are usually used in combination with JAs to resist bacterial stress and delay cold damage in the body.
3.2
aging is
the inevitable physiological process of plants, obviously affecting the product's post-harvest life. Due to the prevalence of endogenous ETH, ABA and other substances related to mature aging, the effect of aging after fruit and vegetable harvesting is not ideal by traditional methods. GAs and CTKs have been shown to inhibit biosynthetic and expression of substances such as ETH and ABA. Therefore, GAs and CTKs store fresh after harvesting of citrus, olive oil, kale and other agricultural products