Impact of Storage Controlled Atmosphere on the Apple Phenolic Acids, Flavonoids, and Anthocyanins and Antioxidant Activity In Vitro

Apples are seasonal fruits, and it is important to prepare them adequately for storage and ensure proper storage conditions. In this study, we used ten different apple cultivars: ‘Alva’, ‘Auksis’, ‘Connell Red’, ‘Cortland’, ‘Ligol’, ‘Lodel’, ‘Noris’, ‘Rubin’, ‘Sampion’, and ‘Spartan’. We studied the qualitative and quantitative composition of phenolic compounds in the apple and apple extracts antioxidants activity before placing them in the controlled atmosphere chambers and again at the end of the experiment, eight months later. Different concentrations of O2, CO2, and N2, constant temperature, relative humidity, and removal of endogenous ethylene were continually maintained. HPLC analysis showed that the highest amount of 2265.7 ± 152.5 µg/g of chlorogenic acid was found in apple samples of the ‘Auksis’ cultivar stored under variant IV conditions. Different concentrations of gas in the controlled atmosphere chambers caused changes in antioxidant activity in whole apple and apple peel extracts. In our study, we found that the antioxidant activity of apple extracts varied between samples of different apple cultivars and depended on the composition of the controlled atmosphere. Determining the optimal storage conditions is beneficial to providing the consumers with apples that have a known and minimally altered chemical composition of phenolic compounds and the strongest antioxidant activity, which determine the use of apples in the healthy food chain.

Development of a new method for determining the degree of ripeness of tomato fruits with different colors of ripe fruits

The paper evaluates the most common sensory, physical, physicochemical and biochemical methods of determining the degree of ripeness of tomato fruits. On the example of small-fruit varieties with red, orange, yellow and brown colors of ripe fruits, an attempt was made to create a universal scale to assess the degree of ripeness of tomato fruits based on the physiological state of the fruits. The paper presents data on the quantitative content of endogenous ethylene in fruits with certain ripeness level.

Re-evaluation of ethylene role in Arabidopsis cauline leaf abscission induced by water stress and rewatering

ABSTRACTPatharkar and Walker (2016) reported that cauline leaf abscission in Arabidopsis is induced by a cycle of water stress and rewatering, which is regulated by the complex of INFLORESCENCE DEFICIENT IN ABSCISSION (IDA), HAESA (HAE), and HAESA-LIKE2 (HSL2) kinases. However, they stated without presenting experimental results that ethylene is not involved in this process. Since this statement contradicts the well-established role of ethylene in organ abscission induced by a cycle of water stress and rewatering, our present study was aimed to re-evaluate the possible involvement of ethylene in this process. For this purpose, we examined the endogenous ethylene production during water stress and following rewatering, as well as the effects of exogenous ethylene and 1-methylcyclopropene (1-MCP), on cauline leaf abscission of Arabidopsis wild type. Additionally, we examined whether this stress induces cauline leaf abscission in ethylene-insensitive Arabidopsis mutants. The results of the present study demonstrated that ethylene production rates increased significantly in cauline leaves at 4 h after rewatering of stressed plants, and remained high for at least 24 h in plants water-stressed to 40 and 30% of system weight. Ethylene treatment applied to well-watered plants induced cauline leaf abscission, which was inhibited by 1-MCP. Cauline leaf abscission was also inhibited by 1-MCP applied during a cycle of water stress and rewatering. Finally, no abscission occurred in two ethylene-insensitive mutants, ein2-1 and ein2-5, following a cycle of water stress and rewatering. Taken together, these results clearly indicate that ethylene is involved in Arabidopsis cauline leaf abscission induced by water stress.One sentence summaryUnlike Patharker and Walker (2016), our results show that ethylene is involved in Arabidopsis cauline leaf abscission induced by water stress and rewatering, similar to leaf abscission in other plants.

Is Endogenous Ethylene Production Associated with Increased Shoot Number in Gentian Cultured In Vitro? Developing a Method for Ethylene Measurement at Nano Level within a Gas-exchangeable In Vitro System

We investigated the possibility of either exogenous ethylene or endogenous ethylene production having an association with the increase in shoot number when nodal explants of Gentiana spp. ‘Little Pinkie’ were cultured in an in vitro medium supplemented with ethephon (10 mg⋅L–1). For the first time within an in vitro system, we report the application of laser ethylene detector technology, and optimization of the methodology to quantify concentrations of ethylene (in the part-per-billion range) released from ethephon decomposition within the atmosphere of gas-exchangeable culture vessels including nodal explants. Compared with continuous (continuous measurements on the same replicate of vessels) and repeated (sampling same replicate of vessels every 48 hours) sampling methodologies, the nonrepeated (sampling fresh replicate of vessels every 48 hours) method of measurement of ethylene concentration was more representative of the actual condition within vessels. Although no prior published data exist showing the positive or negative effect of gaseous ethylene in the headspace of culture vessels on bud outgrowth in gentian, our study shows gaseous ethylene in the headspace of culture vessels was not effective in increasing shoot formation in gentian explants cultured in vitro, whereas ethephon supplementation in agar was effective. Plant material in culture vessels did not have a significant effect on ethylene production regardless of the presence or absence of ethephon. Therefore, although ethephon supplementation in the medium produced gaseous ethylene in the headspace, it was unlikely to cause endogenous ethylene production in explants, but it did trigger shoot formation in ‘Little Pinkie’, perhaps through decomposition to ethylene within the explant tissue, enhancing the internal ethylene level possibly at a locally high concentration.

Stablization of ACOs by NatB mediated N-terminal acetylation is required for ethylene homeostasis

N-terminal acetylation (NTA) is a highly abundant protein modification catalyzed by N-terminal acetyltransferases (NATs) in eukaryotes. However, the plant NATs and their biological functions have been poorly explored. Here we reveal that loss of function of CKRC3 and NBC-1, the auxiliary subunit (Naa25) and catalytic subunit (Naa20) of Arabidopsis NatB, respectively, led to defects in skotomorphogenesis and triple responses of ethylene. Proteome profiling and WB test revealed that the 1-amincyclopropane-1-carboxylate oxidase (ACO, catalyzing the last step of ethylene biosynthesis pathway) activity was significantly down-regulated in natb mutants, leading to reduced endogenous ethylene content. The defective phenotypes could be fully rescued by application of exogenous ethylene, but less by its precursor ACC. The present results reveal a previously unknown regulation mechanism at the co-translational protein level for ethylene homeostasis, in which the NatB-mediated NTA of ACOs render them an intracellular stability to maintain ethylene homeostasis for normal growth and responses.

Proteomic analysis reveals key proteins involved in ethylene-induced adventitious root development in cucumber (Cucumis sativus L.)

The mechanisms involved in adventitious root formation reflect the adaptability of plants to the environment. Moreover, the rooting process is regulated by endogenous hormone signals. Ethylene, a signaling hormone molecule, has been shown to play an essential role in the process of root development. In the present study, in order to explore the relationship between the ethylene-induced adventitious rooting process and photosynthesis and energy metabolism, the iTRAQ technique and proteomic analysis were employed to ascertain the expression of different proteins that occur during adventitious rooting in cucumber (Cucumis sativus L.) seedlings. Out of the 5,014 differentially expressed proteins (DEPs), there were 115 identified DEPs, among which 24 were considered related to adventitious root development. Most of the identified proteins were related to carbon and energy metabolism, photosynthesis, transcription, translation and amino acid metabolism. Subsequently, we focused on S-adenosylmethionine synthase (SAMS) and ATP synthase subunit a (AtpA). Our findings suggest that the key enzyme, SAMS, upstream of ethylene synthesis, is directly involved in adventitious root development in cucumber. Meanwhile, AtpA may be positively correlated with photosynthetic capacity during adventitious root development. Moreover, endogenous ethylene synthesis, photosynthesis, carbon assimilation capacity, and energy material metabolism were enhanced by exogenous ethylene application during adventitious rooting. In conclusion, endogenous ethylene synthesis can be improved by exogenous ethylene additions to stimulate the induction and formation of adventitious roots. Moreover, photosynthesis and starch degradation were enhanced by ethylene treatment to provide more energy and carbon sources for the rooting process.

Exogenous ethylene increases methane emissions from canola by adversely affecting plant growth and physiological processes

It is well known that ethylene affects plants; however, its regulatory role in plant-derived methane (CH4) has not been addressed. In this study, we determined the effects of exogenous ethylene on canola (Brassica napus L.) growth and physiological traits, endogenous ethylene, and aerobic methane emission. Plants were grown under experimental conditions (22/18°C, 16 h light/8 h dark; 500 µmol photons m-2 s-1) for 21 days, and were exposed to exogenous ethylene for different durations (0, 1 or 2 h per day). Methane and ethylene emissions were measured after 7, 14 and 21 days, whereas growth and physiological traits were measured after 21 days. Overall, methane emission decreased, but endogenous ethylene increased, over time with exogenous ethylene. Plants treated with exogenous ethylene had decreased growth, biomass, gas exchange, chlorophyll fluorescence, photosynthetic pigments, and nitrogen balance index, but increased flavonoids. Both methane and ethylene were negatively correlated with most growth and physiological traits. In conclusion, this study revealed that exogenous ethylene significantly increased both endogenous ethylene and methane emissions. It is most likely that plants exposed to exogenous ethylene were stressed and emitted methane, which increased with exposure time.

Postharvest Properties of Ultra-Late Maturing Peach Cultivars and Their Attributions to Melting Flesh (M) Locus: Re-evaluation of M Locus in Association With Flesh Texture

The postharvest properties of two ultra-late maturing peach cultivars, “Tobihaku” (TH) and “Daijumitsuto” (DJ), were investigated. Fruit were harvested at commercial maturity and held at 25°C. TH exhibited the characteristics of normal melting flesh (MF) peach, including rapid fruit softening associated with appropriate level of endogenous ethylene production In contrast, DJ did not soften at all during 3 weeks experimental period even though considerable ethylene production was observed. Fruit of TH and DJ were treated with 5,000 ppm of propylene, an ethylene analog, continuously for 7 days. TH softened rapidly whereas DJ maintained high flesh firmness in spite of an increase in endogenous ethylene production, suggesting that DJ but not TH lacked the ability to be softened in response to endogenous and exogenous ethylene/propylene. DNA-seq analysis showed that tandem endo-polygalacturonase (endoPG) genes located at melting flesh (M) locus, Pp-endoPGM (PGM), and Pp-endoPGF (PGF), were deleted in DJ. The endoPG genes at M locus are known to control flesh texture of peach fruit, and it was suggested that the non-softening property of DJ is due to the lack of endoPG genes. On the other hand, TH possessed an unidentified M haplotype that is involved in determination of MF phenotype. Structural identification of the unknown M haplotype, designated as M0, through comparison with previously reported M haplotypes revealed distinct differences between PGM on M0 haplotype (PGM-M0) and PGM on other haplotypes (PGM-M1). Peach M haplotypes were classified into four main haplotypes: M0 with PGM-M0; M1 with both PGM-M1 and PGF; M2 with PGM-M1; and M3 lacking both PGM and PGF. Re-evaluation of M locus in association with MF/non-melting flesh (NMF) phenotypes in more than 400 accessions by using whole genome shotgun sequencing data on database and/or by PCR genotyping demonstrated that M0 haplotype was the common haplotype in MF accessions, and M0 and M1 haplotypes were dominant over M2 and M3 haplotypes and co-dominantly determined the MF trait. It was also assumed on the basis of structural comparison of M haplotypes among Prunus species that the ancestral haplotype of M0 diverged from those of the other haplotypes before the speciation of Prunus persica.

Postharvest properties of ultra-late maturing peach cultivars and their attributions to Melting Flesh (M) locus: Re-evaluation of M locus in association with flesh texture

The postharvest properties of two ultra-late maturing peach cultivars, ‘Tobihaku’ (TH) and ‘Daijumitsuto’ (DJ), were investigated. Fruit were harvested at commercial maturity and held at 25°C. TH exhibited the characteristics of normal melting flesh (MF) peach, including rapid fruit softening associated with an increase in endogenous ethylene production In contrast, DJ did not soften at all during three-week experimental period even though substantial ethylene production was observed. Fruit of TH and DJ were treated with 5000 ppm of propylene, an ethylene analog, continuously for seven days. TH softened rapidly whereas DJ maintained high flesh firmness in spite of an increase in endogenous ethylene production, suggesting that DJ but not TH lacked the ability to be softened in response to endogenous and exogenous ethylene/propylene. DNA-seq analysis showed that tandem endo-polygalacturonase (endoPG) genes located at melting flesh (M) locus, Pp-endoPGM (PGM) and Pp-endoPGF (PGF), were deleted in DJ. The endoPG genes at M locus are known to control flesh texture of peach fruit, and it was suggested that the non-softening property of DJ is due to the lack of endoPG genes. On the other hand, TH possessed an unidentified M haplotype that is involved in determination of MF phenotype. Structural identification of the unknown M haplotype, designated as M0, through comparison with previously reported M haplotypes revealed distinct differences between PGM on M0 haplotype (PGM-M0) and PGM on other haplotypes (PGM-M1). Peach M haplotypes were classified into four main haplotypes: M0 with PGM-M0; M1 with both PGM-M1 and PGF; M2 with PGM-M1; and M3 lacking both PGM and PGF. Re-evaluation of M locus in association with MF/non-melting flesh (NMF) phenotypes in more than 400 accessions by using whole genome shotgun sequencing data on database and/or by PCR genotyping demonstrated that M0 haplotype was the common haplotype in MF accessions, and M0 and M1 haplotypes were dominant over M2 and M3 haplotypes and co-dominantly determined the MF trait. It was also assumed on the basis of structural comparison of M haplotypes among Prunus species that the ancestral haplotype of M0 diverged from those of the other haplotypes before the speciation of Prunus persica.