Exogenous Ethylene Treatment Research Articles

Characterization of circadian‐regulated mRNAs encoding glycine‐rich RNA‐binding proteins in Pelargonium×hortorum

Two cDNAs, PhGRP1 and PhGRP2, with high sequence identity to genes encoding glycine‐rich RNA‐binding proteins, have been cloned from Pelargonium×hortorum. PhGRP is represented in the P.×hortorum genome by a single copy. DNA sequence analysis of two independently isolated cDNAs, PhGRP1 and PhGRP2, indicates that PhGRP2 represents a partially spliced version of PhGRP1. The additional intron‐like sequence in PhGRP2 contains a termination codon, which would result in translation of a truncated protein. Expression of PhGRP1 was high in petals, pistils, roots and stems, and lower in leaves. PhGRP2 transcripts were less abundant than those of PhGRP1 in all tissues, but were proportionately higher in flower tissues than in roots and stems, and were not detectable in leaves. PhGRP transcripts were highest in stigma and style tissues, but were unaffected by exogenous ethylene treatment or pollination. PhGRP transcript levels fluctuated in a circadian rhythm with maximal accumulation late in the day.

477 Effect of High-temperature Controlled-atmosphere Treatments for Insect Control in `Bartlett' Pear Fruit

High-temperature, controlled-atmosphere treatments were explored for disinfestation of codling moths from `Bartlett' pear fruit. Fruit were freshly harvested in 1996 and 1997 and sorted for uniformity and absence of defects. Fruit were exposed to forced-heating at 46 °C for 1, 2 and 3 h in either air or a controlled atmosphere of 1% oxygen and 15% carbon dioxide. Fruit were evaluated during ripening at 20 °C immediately after treatment (1997 only) and after 3 weeks of cold storage at -1 °C. Fruit were ripened with and without an exogenous ethylene treatment in 1997. Heat treatments, and particularly heat plus CA treatments, slowed fruit ripening, even after fruit had been stored for 3 weeks. The longer the treatment, the greater the inhibition. Fruit from longer treatments were firmer than untreated fruit after 4 days of ripening, but treatment with exogenous ethylene did not overcome the inhibition in the rate of ripening, although fruit from all treatments softened faster. The mortality of codling moths following exposure to the same treatments was also determined. With the heat plus controlled-atmosphere treatments, 100% mortality was achieved in 2.5 h with the faster heating rate used in our 1996 experiment, while it took 3 h to achieve 100% mortality with the slower heating rate.

Aroma Volatile Profiles from Ripe Tomatoes are Influenced by Physiological Maturity at Harvest: An Application for Electronic Nose Technology

The effect of physiological maturity at harvest on ripe tomato (Lycopersicon esculentum Mill.) volatile profiles was studied using ripening response time (in days) to 100 μL·L-1 exogenous ethylene treatment as a tool to separate immature-green from mature-green fruit. Electronic nose (EN) sensor array and gas chromatography (GC) analyses were used to document volatile profile changes in tomatoes that required a 1-, 3-, or 5-day ethylene treatment to reach the breaker stage. EN output analysis using multivariate discriminant and canonical analyses classified intact tomato and whole tomato homogenate samples that required 3 or 5 days of ethylene treatment as significantly different (P < 0.01) from those that required only 1 day. The GC aroma profiles from whole tomato homogenate showed that 1-day fruit had significantly higher levels (P < 0.05) of 1-penten-3-one, cis-3-hexenal, 6-methyl-5-hepten-2-one, 2-isobutylthiazole, and geranylacetone when compared to 5-day fruit. Analysis of excised tomato tissues showed that pericarp (including columnella) produced an average 219% greater concentration of the 16 aroma volatiles quantified by GC when compared to locular gel (442 and 203 μL·L-1, respectively). EN analysis concurred with GC by showing greater average Mahalanobis distance between pericarp tissue groupings when compared to locular gel groupings (78.25 and 12.33 units, respectively). Pericarp tissue from the 5-day ethylene treatment showed significantly lower levels of 1-penten-3-one, trans-2-heptenal, 6-methyl-5-hepten-2-one, 2-isobutylthiazole, geranylacetone, and β-ionone compared to the 1- and 3-day treatments, Similarly, locular gel from the 3- and 5-day ethylene treatments had significantly lower levels of 1-penten-3-one, 2-isobutylthiazole, and 1-nitro-2-phenylethane compared to 1-day samples. cis-3-Hexenol in locular gel was the only volatile compound that showed significantly higher levels with increasing ethylene treatment. EN analysis showed greater Mahalanobis distances between 1- and 3-day ethylene samples than between 3- and 5-day ethylene samples (32.09 and 12.90, 24.14 and 6.52, 116.31 and 65.04, and 15.74 and 13.28 units, for intact tomato, whole tomato, pericarp, and locular gel homogenate, respectively).

Isolation and Characterization of Putative Ethylene Receptor Genes from Zonal Geranium

In this study, the temporal and spatial regulation of putative ethylene receptor genes was examined during ethylene and pollination-induced flower petal abscission of zonal geranium (Pelargonium × hortorum L.H. Bailey). We used the Arabidopsis thaliana ETR1 gene as a heterologous probe to isolate two full-length cDNA clones, GER1 and GER2, from an ethylene-treated geranium pistil cDNA library. Both cDNAs share a high degree of DNA sequence similarity to ETR1, and examinations of deduced amino acid sequences indicate that the proteins encoded by each gene have the conserved ethylene binding and response regulator domains found in ETR1. Experiments focused on determining the temporal regulation of these genes revealed that both genes are expressed in geranium florets much earlier than when the florets become responsive to ethylene treatment, which is sufficient to cause petal abscission in 1 hr. Both genes are expressed in pistils throughout floret development. Experiments focused on determining the spatial regulation of these genes revealed that both genes are expressed at moderate levels in leaves, pistils, anthers, and petals, and are expressed at very low levels in roots. Preliminary evidence suggests that GER2 is transcriptionally regulated by ethylene in pistils after exogenous ethylene treatment. Currently, the transcriptional regulation of these genes in pistils after pollination is unknown.

Postharvest Behavior of Transgenic Cantaloupe Melons with Suppressed ACC Oxidase Activity

We have generated transgenic Cantaloupe Charentais melons expressing an ACC oxidase antisense gene in which ethylene production was reduced to less than 1% as compared to control untransformed fruits. As a consequence, some aspects of the ripening process were strongly inhibited (aroma volatiles production, chlorophyll and cell wall degradation, pigmentation of the rind, activation of peduncular abscission zone) while others remained unchanged (coloration of the flesh), allowing us to distinguish between ethylene-dependent and ethylene-independent pathways. Some postharvest characteristics of the transgenic fruit are described in terms of expression of ripening-related genes, respiratory behavior, and biochemical composition. Data also are presented showing that exogenous ethylene treatments could reverse the antisense phenotype.

Expression of ACC oxidase antisense gene inhibits ripening of cantaloupe melon fruits.

The plant hormone ethylene plays a major role in the ripening of climacteric fruit. We have generated transgenic cantaloupe Charentais melons expressing an antisense ACC oxidase gene; ACC oxidase catalyzes the last step of ethylene biosynthesis. Ethylene production of transgenic fruit was < 1% of control untransformed fruit, and the ripening process was blocked both on and off the vine. The antisense phenotype could be reversed by exogenous ethylene treatment. Analysis of antisense ACC oxidase melons indicated that the ripening process includes ethylene-dependent and ethylene-independent pathways. Because the transgenic line we generated displays extended storage life and improved quality, it has a promising potential for commercial development.

Differential regulation of polygalacturonase and pectin methylesterase gene expression during and after heat stress in ripening tomato (Lycopersicon esculentum Mill.) fruits

The effects of extended heat stress on polygalacturonase (PG; EC 3.2.1.15) and pectin methylesterase (PME; EC 3.1.1.11) gene expression at mRNA, protein and activity levels in ripening tomato fruits were investigated. Steady state levels of PG mRNA declined at temperatures of 27 degrees C and above, and a marked reduction in PG protein and activity was observed at temperatures of 32 degrees C and above. Exogenous ethylene treatment did not reverse heat stress-induced inhibition of PG gene expression. Transfer of heat-stressed fruits to 20 degrees C partly restored PG mRNA accumulation, but the rate of PG mRNA accumulation declined exponentially with duration of heat stress. Heat stress-induced inhibition of PME mRNA accumulation was recoverable even after 14 days of heat stress. In fruits held at 34 degrees C, both PG and PME protein and activity continued to accumulate for about 4 days, but thereafter PG protein and activity declined while little change was observed in PME protein and activity. In spite of increases in mRNA levels of both PG and PME during the recovery of heat-stressed fruit at 20 degrees C, levels of PG protein and activity declined in fruits heat-stressed for four or more days while PME protein and activity levels remained unchanged. Collectively, these data suggest that PG gene expression is being gradually and irreversibly shut off during heat stress, while PME gene expression is much less sensitive to heat stress.

Differential Expression of the Two Subunits of Tomato Polygalacturonase Isoenzyme 1 in Wild-Type and rin Tomato Fruit.

The [beta] subunit of tomato (Lycopersicon esculentum Mill.) fruit polygalacturonase 1 is a cell wall glycoprotein that binds to and apparently regulates the catalytic PG2 polypeptide in vivo. [beta] Subunit and polygalacturonase 2 (PG2) expression have been investigated in both wild-type and ripening inhibitor (rin) mutant fruit. During fruit development and ripening, [beta] subunit expression was unrelated to expression of the catalytic PG2 protein. In wild-type fruit, [beta] subunit mRNA and protein were first detected early in development and increased to maximal levels before PG2 mRNA and protein were detected. At the onset of ripening [beta] subunit mRNA decreased dramatically, but [beta] subunit protein levels remained stable. In rin fruit, which fail to ripen, [beta] subunit expression was similar to that in wild type, although PG2 mRNA and protein were not detected. These data suggest that [beta] subunit expression is ethylene independent and regulated primarily by developmental cues. This conclusion is supported by results from ethylene-treated immature (20 days after pollination) wild-type and rin fruit in which no significant differences were observed in [beta] subunit expression patterns in response to ethylene treatment. Surprisingly, RNA blot analysis indicated that catalytic PG2 mRNA was induced in immature rin fruit after 3 d of exogenous ethylene treatment. In addition, [beta] subunit mRNA and protein were also detected at lower levels in root, leaf, and flower tissues of both genotypes, suggesting a broader functional role for the protein.

Effect of ethylene treatment on ethylene production, EFE activity and ACC levels in peel and pulp of banana fruit

Exogenous ethylene treatment (100 ppm) induces preclimacteric bananas ( Musa acuminata Collar. cv. Dwarf Cavendish) to ripen with increased respiration and endogenous ethylene production; 12 h treatment was slightly more effective than 6 h. In transverse sections of bananas the contribution of the peel to respiratory and ethylene increases after induction by exogenous ethylene was negligible and the pulp provided all the output. Increases in respiratory CO 2 and ethylene by banana slices were generally in line with the inductive period of ethylene treatment. Banana slices treated with ethylene show an increase in EFE activity in both peel and pulp, with that in the peel being shown earlier. The effect is related to the duration of treatment. Ethylene-treated slices contained higher levels of conjugated ACC, but not free ACC, than control slices, but there was no clear link with the length of exposure to exogenous ethylene. The increase in ACC conjugation activity could explain the initial lower ethylene production shown by slices treated with exogenous ethylene.

Pleiotropic Effects of sym-17

R82 (sym-17), a stable mutant of Pisum sativum L. cv Sparkle, is described. The shoot growth of the mutant was less than that of its parent under light or dark growth conditions. Gibberellic acid treatment did not normalize the shoot growth of R82. The mutant had thick and short roots. It formed few nodules, but the specific nitrogenase activity was not affected. R82 produced and contained more ethylene than Sparkle. It also contained more free 1-amino-cyclopropane-1-carboxylic acid than did its parent in both the shoot and the root. The root tip of R82 had a lower activity of ethylene-forming enzyme than that of Sparkle, whereas the whole shoot of R82 had a similar activity. The sensitivity of R82 to exogenous ethylene was not more than that of Sparkle. Exogenous ethylene treatments did not make Sparkle mimic R82, and inhibitors of ethylene biosynthesis or action did not normalize the phenotype of R82. The data suggest that the primary effect of sym-17 is not the enhanced ethylene production.

4924485 Portable radiography system using a relativistic electron beam : Robert F Hoeberling

Fruit ethylene production and flesh firmness were measured in F1 and F2 offsprings from a cross of a non-melting cultivar ‘Nishiki’ and a stony hard cultivar ‘Yumyeong’ of peach (Prunus persicaBatsch). Fruits from genotypes that showed no natural ethylene production were treated with 1000 ppm ethylene and subsequent flesh softening was observed. Genotypes of melting and non-melting in stony hard fruits could be distinguished by the degree of softening following exogenous ethylene treatment. The stony hard trait was inherited independently of the melting flesh/non-melting flesh trait and was epistatic to this trait.

Epinasty promoted by salinity or ethylene is an indicator of salt‐sensitivity in tomatoes

Abstract Six genotypes of tomato (Lycopersicon esculentum Mill.) that differ in their salt‐tolerance, were exposed to 200 mol m−3 NaCl for 4 weeks. Seedlings exhibited a marked decline in shoot dry weight accumulation and increased petiolar epinasty after exposure to salinity stress. Ranking accessions on the basis of their relative growth reduction in response to salinity, provided good agreement with the level of epinasty promoted during the salinity treatment. In the absence of salt‐stress, leaf epinasty promoted by exogenous ethylene treatment was found to be a positive indicator of the genotypes incipient salt‐sensitivity. Endogenous ethylene levels in untreated plants were negatively correlated with ethephon‐induced epinasty. Genotypes with normally high endogenous C2H4 levels were less responsive to ethephon treatment and also exhibited greater salt‐tolerance than genotypes with low endogenous C2H4 levels. These observations are consistent with the suggestion that a main feature of adaptation in the genotypes examined may involve modulation of their cellular sensitivity to C2H4. The results indicate that leaf epinasty, whether salt‐ or ethylene‐induced, is a sensitive indicator of salt‐sensitivity. Ethylene‐induced epinasty may, therefore, provide a simple basis upon which to identify and select salt‐tolerant plants.

Carbon Dioxide Enhances the Development of the Ethylene Forming Enzyme in Tobacco Leaf Discs

Since CO(2) is known to stimulate ethylene production by promoting the conversion of 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene, the effect of CO(2) on the activity and the development of the ethylene forming enzyme (EFE) was studied in tobacco (Nicotiana tabacum L. cv Havana 425 and Xanthi) leaf discs. In addition to previous observations that EFE activity is dependent on CO(2) concentration and is saturable with 2% CO(2), present data show two saturation curves at 2% and 10% CO(2). Promotion of EFE development was dependent also on CO(2) concentration (saturated at 2% CO(2)) and duration (maximum at 24 in the dark), and was abolished by 20 micromolar cycloheximide. Application of exogenous ethylene (20 microliters per liter) or light treatment further increased the CO(2)-enhanced development of EFE, implying that these two factors can also affect EFE development via interaction with CO(2). The results suggest that CO(2) exerts its stimulatory effect on the conversion of ACC to ethylene by enhancing not only the activity but also the synthesis of EFE in leaf discs.

The Maturation and Ripening of the ‘Wonderful’ Pomegranate

Abstract Pomegranate (Punica granatum L. ‘Wonderful’) fruit reached horticultural maturity for commercial harvest when the soluble solids content (SSC) attained a fairly constant level of 15%. The level of titratable acidity (TA) varied from one location to another and from one year to the next but also generally remained stable at the same time that the SSC reached 15%. After harvest, there was no further change in either SSC or TA at 20°C, but redness of the juice continued to increase in intensity up to and after harvest. The respiration pattern of the mature fruit was of the nonclimacteric type, with only traces of ethylene evolved on occasion. Ethylene treatment of the fruit caused a rapid transient rise in CO2 evolution but no changes in SSC, TA, and fruit or juice color. A pseudo-climacteric pattern of respiration was found in very young immature fruit. The respiration rate of dehisced arils paralleled that of the intact fruit, but there was no response to exogenous ethylene treatment. Ethylene evidently stimulated the CO2 output only of the fruit rind.

果実&amp;bull;野菜の成熟生理と貯蔵に関する研究 (第2報)

The changes in respiration rates, ethylene production, internal ethylene concen trations and flesh firmness were investigated during the maturation and ripening periods of pear fruits, using 3 species and several cultivars, as follows: Pyrus communis L. var. sativa DC. (Bartlett, La France and Winter Nelis), Pyrus serotina Rehd. var. culta (Yakumo, Nijisseiki, Niitaka and Kikusui), Pyrus ussuriensis Maxim. var. sinesis Kikuchi (Ya-li, Rai-Yan-Tsu-li and Auto-li). The fruits were picked 2-3 times at different stages of maturity and stored at 20°C.1. Three cultivars of P.communis, Bartlett, La France, and Winter Nelis showed a typical climacteric pattern of respiration. Respiration and ethylene production in both La France and Winter Nelis were much lower than in Bartlett.2. Among P.serotina, Yakumo and Kikusui fruits picked at two different stages of maturity showed a rise in respiration; respiration didn′t rise in Nijisseiki and Niitaka fruits picked at commercial harvest maturity, but did in fruits picked at the immature stage. Ethylene production in Yakumo increased with rising respiration, but the other 3 cultivars maintained a very low level of production during the experimental period.In Nijisseiki, exogenous ethylene treatment caused a rise in respiration immedi ately after picking. This effect continued only in the presence of exogenous ethylene, and could be reproduced in the same fruit when re-treated with ethylene after a month of storage.It was concluded that Yakumo and Kikusui can be classified as climacteric fruits, while Nijisseiki and Niitaka are non-climacteric fruits.3. Three cultivars of P.ussuriensis; Ya-li, Rai-Yan-Tsu-li and Auto-li showed a typical climacteric accompanying a rise in ethylene production.

Ethylene Production and Respiratory Behavior of the rin Tomato Mutant

Little or no change in ethylene or CO(2) production occurred in rin tomato mutant fruits monitored for up to 120 days after harvest. Of the abnormally ripening tomatoes investigated, including "Never ripe" (Nr Y a h, Nr c l(2) r), "Evergreen" (gf r) and "Green Flesh" (gf), only rin did not show a typical climacteric and ethylene rise.Fruits from F(1) plants resulting from reciprocal crosses between rin and normal plants apeared to ripen normally, but when compared to normal fruit, their ripening was delayed as measured by ethylene and CO(2) production and color change. These fruits produced only one-third to one-half as much ethylene at the peak of production compared to normal fruits.Exogenous ethylene or propylene treatment did not stimulate ethylene production by rin fruits but did stimulate CO(2) production. The CO(2) stimulation persisted only in the presence of the exogenous olefins. Stimulation of CO(2) production could be repeated several times in the same fruit. Wounding stress stimulated both ethylene and CO(2) production in rin fruits. It was concluded that rin tomato fruits behave like nonclimacteric fruits.