1-MCP Research Articles

MaExp1, an ethylene-induced expansin from ripening banana fruit

Expansins are known to participate in several processes during plant growth and development particularly where wall extension and cell expansion are required. These are also believed to prepare cell wall for their subsequent degradation by cell wall hydrolases during ripening particularly in climacteric fruits. The identification and characterization of a fruit-specific expansin, MaExp1, gene is reported here for the first time from banana. The MaExp1 cDNA of 1098 bp encodes a polypeptide of 255 amino acids, which has all the characteristics of an α-expansin. Ethylene exposure to unripe mature banana fruit induces MaExp1 expression, which increases with the progression in ripening and 1-MCP (1-methyl cyclopropene) treatment prior to ethylene exposure inhibits expression. No expression has been detected in any other tissue. The genomic sequence analysis has revealed that MaExp1 contains two short introns of 83 and 79 nucleotides. The 888 bp proximal promoter of the gene shows presence of a putative ethylene and auxin responsive elements and a direct repeat with in the sequence. The IAA treatment enhanced MaExp1 expression only in the presence of ethylene suggesting its effect as synergistic and additive. It is suggested that MaExp1 could be used for manipulating ripening in banana and its promoter could be a suitable candidate for expressing foreign gene (vaccines) in transgenic banana fruit.

Physiological and biochemical characterization of ethylene-generated gravicompetence in primary shoots of coleoptile-less gravi-incompetent rye seedlings.

A recent study demonstrated that gravi-incompetent coleoptile-less seedlings of rye exhibit gravi-competence after exogenous application of ethylene. Treatments and conditions which induce and interfere with this phenomenon were analysed in more detail. Aminocyclopropane-1-carboxylic acid (ACC) as a precursor of ethylene has similar gravicompetence-inducing effects and also appropriate conditions of light, which strongly enhances ethylene synthesis. Both effects can be inhibited by the ethylene-perception blocking agent methylcyclopropene (MCP) or inhibitors of ethylene synthesis such as aminovinylglycine (AVG), indicating that light exerts its gravicompetence-generating effect via induced/enhanced ethylene synthesis. Gain in gravicompetence is accompanied by the induced/enhanced occurrence of calreticulin and lipoxygenase as detected by 2D-gels and Q-TOFF-analyses. Previously gravicompetent, light-grown coleoptile-less seedlings are characterized by gravi-incompetent growth during subsequent horizontal gravistimulation when perception of ethylene is inhibited by MCP. The results demonstrate that continuous perception of ethylene is an indispensable step, permanently required for the regulation of gravitropic growth in germinating primary shoots of rye, either within the process of graviperception and/or of the transduction of the gravi-signal.

EFFECTS OF MCP AND LIGHT ON POSTHARVEST COLOUR DEVELOPMENT IN APPLES

The red colour in apple peel is caused by anthocyanin pigments and is a major part of consumers’ choice of apples. ‘Rome’ apple fruit were bagged with double lined paper bags in the orchard several months before harvest. This prevented any preharvest anthocyanin development. A factorial experiment using 1-methyl cyclopropene (MCP) and storage under fluorescent light at 20°C was conducted on preclimacteric apples. Peel colour, chlorophyll fluorescence and internal ethylene were measured for 28 days after harvest. Light was shown to be absolutely essential for the development of peel anthocyanins. All bagged apples stored in the dark did not develop full colour. Bagged fruit stored in the dark and treated with MCP remained green for the entire experiment whilst those bagged fruit without MCP treatment showed some red colouration and chlorophyll degradation. Bagged apples stored in the light, which did not receive MCP treatment, began to develop colour within one day, where MCP treated fruit produced some colour, but never to the same extent as fruit not treated with MCP. Colour development was also enhanced in control (non-bagged) fruit stored in the light but not those stored in the dark. Further work is continuing on the regulation of anthocyanin production.

Blocking ethylene perception enhances flooding tolerance in rice seedlings.

Large areas of rainfed lowlands in South and Southeast Asia annually experience short durations of flash flooding during the rice-growing season, which dramatically affect plant survival and productivity. Submergence-intolerant cultivars usually show progressive leaf chlorosis, which could be triggered by ethylene produced during submergence. An ethylene inhibitor, 1-methyl cyclopropene (MCP), was used to evaluate the effect of ethylene on chlorophyll degradation and plant survival. Seedlings of two cultivars, FR13A (tolerant) and IR42 (intolerant) either untreated or treated with MCP for 5 h before submergence, were submerged for 6 d. Chlorophyll content and activity and gene expression of chlorophyllase, the first enzyme involved in chlorophyll degradation, were determined during submergence and recovery, and survival scores were recorded after 21 d of recovery. MCP treatment decreased chlorophyll degradation, lowered the activity and gene expression of chlorophyllase, and improved seedling survival in IR42, but with no effect on underwater relative shoot expansion. Chlorophyllase enzyme activity and gene expression were lower in FR13A, suggesting that this cultivar might have reduced ethylene level or sensitivity. Manipulation of ethylene synthesis or sensitivity through molecular approaches might therefore help improve tolerance of flash flooding in rice.

Two expansin cDNAs from Prunus armeniaca expressed during fruit ripening are differently regulated by ethylene

Little is known about gene expression during fruit ripening of apricot ( Prunus armeniaca L. cv. Bergeron), especially for enzymes involved in cell wall modifications. A partial cDNA clone encoding a protein homologous to expansin was isolated from a ripe apricot fruit cDNA library. This clone was used to isolate two full-length expansin cDNAs, Pa-Exp1 (accession no. U93167) and Pa-Exp2 (accession no. AF038815) from the same cDNA library. The predicted polypeptides encoded by these two cDNAs are different and belong to the α-expansin family; Pa-Exp1 and Pa-Exp2 are two different members of a multigene family. These two clones are mostly expressed in fruit, during its ripening. Pa-Exp1 mRNA accumulated abundantly at the half-ripe stage of fruit development and decreased thereafter. Pa-Exp2 mRNA level increased from the immature-green stage to the half-ripe stage where it peaked before declining. During the ripening process, Pa-Exp1 and Pa-Exp2 gene expression appeared to be positively correlated with fruit size. Post-harvest treatments by air, ethylene, and 1-methyl cyclopropene led us to conclude that Pa-Exp1 appears to be developmentally down-regulated by ethylene while Pa-Exp2 is not affected. The relationship between Pa-Exp1, Pa-Exp2 and the softening process is also discussed.

Reaction of allylboranes with methylcyclopropene

Reaction of allylboranes with methylcyclopropene

Copolymers of 1‐methylcyclopropene

Abstract1‐Methylcyclopropene (MCP) copolymerizes rapidly with acrylic and vinyl monomers to form soluble, high molecular weight products containing enchained cyclopropane rings. The high electron availability in the cyclopropene double bond promotes one‐to‐one alternating copolymerization with sulfur dioxide, maleic anhydride, acrylic acid, acrylonitrile, dialkyl fumarates and acrylic esters. Nonalternating copolymers are obtained with vinyl chloride and vinyl acetate, and attempted copolymerization fails entirely with styrene, α‐methylstyrene and isoprene. This pattern of copolymerization reactivity resembles that of highly compressed ethylene. Methylcyclopropene copolymers have high glass temperatures in spite of the small size of the MCP unit. The combination of high Tg and small size allows preparation of copolymers with high Tg having a wide range of ductilities and cohesive energy densities.

Infrared and Raman spectra of 1-methylcyclopropene

Abstract 1-Methyl cyclo propene is unique in that it contains a carbon-carbon double bond in a strained three-membered ring with methyl, methylenic and vinylic protons present. The molecule has C 3 symmetry and possesses 24 fundamental vibrations: 15 a ' + 9 a ″. Vapor and solid phase infrared (250–4000 cm −1 ) and liquid phase Raman spectra have been obtained and a study of the molecular vibrations, as revealed by its spectrum, has been completed. Assignment of the fundamentals has been made from vapor phase band contours, characteristic group frequencies and Raman polarization data.