Biotechnology Coronatine Has A Significant Effect On Color Improvement And Sugar Increasing In Fruits Such As Apple, Tomato, Citrus, And Grape

1. Overview Of the Development of The Global Fruit Industry

Fruit is one of the world's major agricultural products, which not only contains rich nutrients, but also has various health benefits such as lowering blood pressure, slowing aging, improving eyesight, fighting cancer, and lowering cholesterol. Currently, there are a wide variety of fruits in the world, with a large market consumption. Common fruits include 33 families, and based on an estimated 1000 types per family, there are expected to be 33000 types of fruits worldwide. Since 1990, the production and output value of major fruits worldwide have shown an increasing trend, while the consumption trend has developed towards convenience, portability, and freshness. According to statistics from the United Nations and the Agricultural Organization of 193 core countries worldwide, the global fruit planting area in 2019 was 620.825 million hectares, with a yield of 883.413 million tons. The top ten fruits in the world were bananas (including plantains), oranges, watermelons, apples, grapes, pears, peaches, pineapples, lemons, and plums. Among them, the yield of bananas was 211.871 million tons, ranking first in global fruit production, followed by 210.765 million tons of citrus; Watermelon followed closely at 197.297 million tons. The top three countries in terms of fruit production and planting area are China (274 million tons), India (104 million tons), and Brazil (40.098 million tons), with China's fruit planting area of 2740.8 thousand hectares, India's 7065.9 thousand hectares, and Brazil's 20924 thousand hectares.

Fig.1: Global Fruit Planting Yield and Area From 2014 To 2020

2. Global Fruit Color Conversion Issues and Demand

In recent years, the concept of "green and natural" has become popular, and people's demand for fruits is increasing day by day. The concept of "superfood" is popular in North America, Japan, Australia, and some European countries, with various fruits such as apples, strawberries, figs, blueberries, guava, and kiwifruit being referred to as "superfood" ("superfood" refers to a variety of foods that can provide high energy and nutrients, provide the energy needed by the human body, improve dietary habits, and not only provide rich nutrition, but also be grown in an environmentally friendly manner). However, fruits all over the world are generally faced with the problem of color change. The appearance quality of fruits is seriously affected by slow coloring, non-coloring, and turning green after coloring during the color change period, and the market value, processing use, and quality of processed products of fresh fruits and vegetables are greatly affected ^[1]. According to production calculations, among the top ten global fruits in 2019, seven types, including bananas, oranges, apples, grapes, peaches, pineapples, and plums, had a demand for early release of "coloring improvement and sugar content increasing", accounting for over 90% of the global fruit production. Conservatively, the current color conversion market capacity is estimated to be billions of dollars.

3. Global Fruit Color Improvement Solutions

Previous studies have shown that the color of fruits is the result of highly modified pigments such as chlorophyll, carotenoids, and anthocyanins ^[2], which are determined by genetic factors and also influenced by external environment and cultivation measures. Chlorophyll and carotenoids determine the base color, while anthocyanins determine the surface color. The combination of base color and surface color can combine to form different appearance colors. This process is accompanied by the metabolism of internal cell walls of fruits, the accumulation of aromatic compounds antioxidant and polyphenol synthesis, hormone content changes, ultimately reaching an edible level, gradually exhibiting the inherent color and aroma of the variety ^[3-5]. Therefore, regulating the synthesis of characteristic pigments, the synthesis of mature related metabolites, and changes in hormone content are the key to uniform fruit coloring and quality improvement.

At present, among the main color conversion products in the market, the requirements for the use time and dosage of growth regulators (ethephon) are relatively strict. If there is a slight mistake, the fruits may become soft, dark, easy to fall off, the storage and transportation resistance of the fruit may decrease, and even cause many problems such as defoliation and tree vigor decline ^[6-7]. Biostimulants (peptides, enzymes, active molecules, etc.) are expensive and have different color conversion effects. Nutritional color conversion products are mostly registered and sold as amino acid water-soluble fertilizers or organic water-soluble fertilizers, with strict usage requirements and multiple uses. Under adverse conditions, color conversion effects cannot be guaranteed. Therefore, the market urgently needs a green, safe, and effective color conversion product to solve the above problems.

How to regulate the ordered changes of characteristic pigments, ripening related metabolites, and hormones during the color transformation process is the key to solving the problem of fruit color transformation and quality improvement. The new plant growth regulator COR, brand name "Sweet Crown", provides a solution to the global fruit color change problem. As a jasmonic acid molecular signal regulator, the main component of "Sweet Crown",CORONATINE, activates anthocyanin, anthocyanidin and other biosynthetic pathways by inducing plant gene expression, improves the accumulation of photosynthetic rate, internal proteins, amino acids, sugars and other substances, and solves the problem of fruit color conversion.The key issue in the ripening process is to promote uniform fruit coloring and quality improvement.

Fig. 2: The Novel Plant Growth Regulator Coronatine

4. Novel Plant Growth Regulators Coronatine

4.1 The Discovery of Coronatine

CORONATINE (COR) is a newly developed plant growth regulator that exists in natural plants and is non-toxic and harmless to humans and animals. In 1977, Ichihara et al. separated it from the culture medium of Pseudomonas syringae pv. atropurpurea and named it Coronatine (COR) ^[10]. It is a biological toxin that can cause verticillium wilt in plants at high concentrations. Later studies found that the physiological function of this ingredient is similar to that of jasmonic acid, abscisic acid, etc. Finally, it was renamed as Coronatine on May 3, 2013, led by Chengdu Newsun Crop Science Co., Ltd. and approved by the China Standardization Technical Committee.

4.2 The Industrialization Road of Coronatine

Since the discovery of Coronatine in 1977, how to efficiently obtain Coronatine product has always been a hot topic in Coronatine related research. After years of research and exploration, two synthetic methods, chemical synthesis and biosynthesis, have been established for the synthesis of Coronatine. However, both methods have their own shortcomings. The chemical synthesis of Coronatine is cumbersome and the yield is low, and the production capacity of wild strains fermented by microorganisms is generally low, which cannot meet the requirements of current industrial production. In addition, there are also problems such as low yield, long fermentation cycle, high energy consumption, and high production costs, The slow progress in the industrialization of Coronatine has greatly affected its application in agriculture. With the global emphasis on the development and application of new, safe, and efficient pesticides, China has taken the lead in launching relevant high-tech research and development plans. After 20 years of scientific research, it has successfully used transposon induced mutation, gene recombination, and other methods to construct genetically engineered bacteria with high yield of Coronatine, increasing the production of Coronatine by more than 10 times. And established the world's first Coronatine fermentation production line at Chengdu Newsun Crop Science Co., Ltd. Afterwards, the industrialization of Coronatine has developed rapidly, with membrane concentration, recrystallization and other Coronatine extraction and purification technologies optimized for nutrition, solving the problems of low fermentation potency and yield of Coronatine. Currently, fermentation technology, extraction process, production costs, and other aspects have met the requirements of Coronatine industrialization production. According to the China Pesticide Information Network, in September 2021, Chengdu Newsun Crop Science Co., Ltd. officially obtained the world's first 98% Coronatine TC Registration Certificate (registration certificate number: PD20211351) and the world's first 0.006% Coronatine SL Registration Certificate (registration certificate number: PD20211370).

Fig. 3: Coronatine 98% TC Registration Certificate and Coronatine 0.006% SL Registration Certificate

4.3 Notable Functions and Mechanism of Action of Coronatine

Coronatine (COR) is a structural analog of Jasmonic Acid (JA). Studies have found that COR is 100-10000 times more active than Jasmonic Acid (JA) by binding to JA receptor COI1 (COR sensitive 1) ^[11], showing different application effects at different concentrations ^[12]. When COR enters plant cells, it generates two signal branches, one of which is the hormone system. COR and JA share a common receptor, COI1. The receptors for IAA, JA, and gibberellin are SCF complexes composed of ASK, CUL, and RBX. Therefore, COR can affect the IAA, JA, and gibberellin pathways through receptor COI1; COR also promotes stomatal reopening through the E3 ligase subunit COI1, and the pathway of stomatal closure involves triggering salicylic acid (SA) and abscisic acid (ABA) signaling pathways; Due to the similarity between the precursor ACC of ethylene and the precursor CMA of COR, COR can increase the production of ethylene in plants. In short, COR can manipulate almost all hormone signaling pathways, which is also the reason why coronamycin can regulate many physiological and chemical processes such as plant growth and development and stress. Another signal branch is physiological metabolism. COR induces upregulation of protein expression levels, regulating the cell membrane system, osmotic regulation, photosynthesis system, and antioxidant system, helping plants resist stress damage.

Fig.4: Mechanism of action of COR

5. Application Of Fruit Coloring Enhancement and Sugar Content Increasing of Coronatine

Transcriptome and metabolome studies have shown that moderate concentrations of COR (1-10 μM) can directly or indirectly stimulate ethylene synthesis to induce plant gene expression, promote the activation of biosynthetic pathways such as anthocyanins and anthocyanidin, as well as the accumulation of high-level anthocyanins in the peel and flesh ^[13], promote uniform fruit coloring, and improve fruit color and sweetness. A large number of field trials have also verified its correctness.

5.1 The Effect of COR on the Quality of Grape (Summer Black)

The experimental results showed that applying one application of COR during the grape coloring stage can accelerate the color conversion process, complete the conversion 5-7 days earlier, increase the sugar content by 60%, reduce acidity by 22.8%, and improve quality (Figure 5).

Fig.5: The Effect of COR on the Quality of Grape (Summer Black)

5.2 The Effect of COR on the Quality of Apple

The experimental results showed that using one application of COR on apples can significantly improve the coloring rate, achieve more uniform coloring, reach a coloring index of over 95%, far higher than the control group, and significantly improve fruit quality. Among them, the soluble sugar content of the fruit increased by more than 30% (Figure 6).

Fig. 6: The Effect of COR on the Quality of Apple

5.3 The Effect of COR on the Quality of Citrus

The experimental results showed that using COR twice on the citrus by foliar spray every 15 days resulted in the entire fruit being colored, with a beautiful red color and almost no turning green phenomenon. However, the control group had partially colored and dark colors, and the taste of the fruit in the COR group was significantly improved during the picking period, with an average increase of about 20% in soluble solids content.

Fig.7: The Effect of COR on the Quality of Citrus

5.4 The Effect of COR on the Quality of Pitaya

The experimental results showed that after using COR during the coloring stage of pitaya, the color was bright, with green scales that did not age, and the quality was significantly improved (Figure 8).

Fig. 8: The Effect of COR on the Quality of Pitaya

5.5 The Effect of COR on the Quality of Tomato

The experimental results showed that after using COR on tomatoes, the color conversion was completed 7-10 days earlier, resulting in a significant improvement in color and taste, and enhanced commercial value (Figure 9).

Fig. 9: The Effect of COR on the Quality of Tomato

5.6 The Effect of COR on the Quality of Strawberry

The experimental results showed that after using COR on strawberries, the color conversion was completed 4-6 days in advance, with uniform color and significant improvement in color and taste (Figure 10).

Fig. 10: The Effect of COR on the Quality of Strawberry

In summary, as an environmentally friendly biological plant growth regulator, COR can not only improve the external quality of fruits by making them evenly colored and more marketable, but also improve the internal quality by increasing sugar content, balancing sugar acid ratio, improving taste significantly, and solving problems such as "shady fruits" caused by uneven lighting in apples, grapes, citrus, etc. In addition, as an environmentally friendly new plant growth regulator with high physiological activity, COR not only improves the quality of agricultural products, but also inhibits the increase of unnecessary reactive oxygen species levels in plants, reduces the risk of plant fruit softening and rapid cell disintegration, and prolongs the storage and shelf life of the fruit. This will play an increasingly important role in the healthy and fast sweetening and coloring of fruits.

6. The Market Potential of COR In Fruit Color Conversion and Sugar Content Increasing

With the continuous development and progress of science and technology, the call to reduce the use of chemical pesticides and protect the human living environment is increasing. Research, development and utilization, and the development of green and healthy color conversion products have become one of the important research topics for global scientific workers. As a new plant growth regulator worldwide, COR fundamentally solves the problems of uneven fruit coloring and decreased quality by regulating characteristic pigment synthesis, maturation related metabolite synthesis, and hormone content changes. While promoting fruit coloring, it can also reduce acidity and increase sugar, making the taste of the fruit better, without causing the weakness of soft fruits and tree vigor. Compared to traditional color conversion extraction products, the effective active ingredients of COR are completely present and sourced from natural ecosystems, with no residue after use, and the impact on non-target organisms is relatively small. It is safe for the environment and agricultural products, and more in line with the global consumer demand for safe and environmentally friendly inputs. It is a major trend in the development of green and healthy color conversion products, and the best choice for "uniform coloring and increased sugar content" in fruit cultivation, with broad global application prospects

Reference:

[1] Barrett D M, Beaulieu J C, Shewfelt R. Color, flavor, texture, and nutritional quality of fresh-cut fruits and vegetables: desirable levels, instrumental and sensory measurement, and the effects of processing[J]. Critical reviews in food science and nutrition, 2010, 50(5): 369-389.

[2] Wang Z, Cui Y, Vainstein A, et al. Regulation of fig (Ficus carica L.) fruit color: metabolomic and transcriptomic analyses of the flavonoid biosynthetic pathway[J]. Frontiers in Plant Science, 2017, 8: 1990.

[3] Forlani S, Masiero S, Mizzotti C. Fruit ripening: the role of hormones, cell wall modifications, and their relationship with pathogens[J]. Journal of Experimental Botany, 2019, 70(11): 2993-3006.

[4] Burg S P, Burg E A. Ethylene Action and the Ripening of Fruits: Ethylene influences the growth and development of plants and is the hormone which initiates fruit ripening[J]. Science, 1965, 148(3674): 1190-1196.

[5] Bouzayen M, Latché A, Nath P, et al. Mechanism of fruit ripening[M]//Plant developmental biology-Biotechnological perspectives. Springer, Berlin, Heidelberg, 2010: 319-339.

[6] ABDEL‐GAWAD H, ROMANI R J. Hormone‐Induced Reversal of Color Change and Related Respiratory Effects in Ripening Apricot Fruits[J]. Physiologia Plantarum, 1974, 32(2): 161-165.

[7] Fenn M A, Giovannoni J J. Phytohormones in fruit development and maturation[J]. The Plant Journal, 2021, 105(2): 446-458.

[8] Katsir L, Schilmiller A L, Staswick P E, et al. COI1 is a critical component of a receptor for jasmonate and the bacterial virulence factor coronatine[J]. Proceedings of the National Academy of Sciences, 2008, 105(19): 7100-7105.

[9] Uppalapati S R, Ayoubi P, Weng H, et al. The phytotoxin coronatine and methyl jasmonate impact multiple phytohormone pathways in tomato[J]. The Plant Journal, 2005, 42(2): 201-217.

[10] Ichihara, A., et al., The structure of coronatine. Journal of the American Chemical Society, 1977. 99(2): p. 636-637.

[11] Zhou, Y., et al., Phytotoxin coronatine enhances heat tolerance via maintaining photosynthetic performance in wheat based on Electrophoresis and TOF-MS analysis. Scientific Reports, 2015. 5(1): p. 13870.

[12] Zhang L, et al. Host target modification as a strategy to counter pathogen hijacking of the jasmonate hormone receptor[J]. Proceedings of the National Academy of Sciences, 2015, 112(46): 14354-14359.

[13] Xie Z, et al. Coronatine alleviates salinity stress in cotton by improving the antioxidative defense system and radical-scavenging activity[J]. Journal of Plant physiology, 2008, 165(4): 375-384.