果实成熟乙烯相关基因工程研究进展(综述)

果实成熟是一个复杂的生理生化过程,而乙烯是引发果实成熟的主要因素.本文简述乙烯合成过程中S-腺苷甲硫氨酸水解酶、ACC合成酶与ACC氧化酶、ACC脱氨酶基因和乙烯受体突变体的特性及克隆;同时,评述利用基因工程技术控制果实成熟的应用前景.     

Ethylene and fruit ripening

The latest advances in our understanding of the relationship between ethylene and fruit ripening are reviewed. Considerable progress has been made in the characterisation of genes encoding the key ethylene biosynthetic enzymes, ACC synthase (ACS) and ACC oxidase (ACO) and in the isolation of genes involved in the ethylene signal transduction pathway, particularly those encoding ethylene receptors ( ETR ). These have allowed the generation of transgenic fruit with reduced ethylene production and the identification of the Nr tomato ripening mutant as an ethylene receptor mutant. Through these tools, a clearer picture of the role of ethylene in fruit ripening is now emerging. In climacteric fruit, the transition to autocatalytic ethylene production appears to result from a series of events where developmentally regulated ACO and ACS gene expression initiates a rise in ethylene production, setting in motion the activation of autocatalytic ethylene production. Differential expression of ACS and ACO gene family members is probably involved in such a transition. Finally, we discuss evidence suggesting that the NR ethylene perception and transduction pathway is specific to a defined set of genes expressed in ripening climacteric fruit and that a distinct ETR pathway regulates other ethylene-regulated genes in both immature and ripening climacteric fruit as well as in non-climacteric fruit. The emerging picture is one where both ethylene-dependent and -independent pathways coexist in both climacteric and non-climacteric fruits. Further work is needed in order to dissect the molecular events involved in individual ripening processes and to understand the regulation of the expression of both ethylene-dependent and -independent genes.     

Manipulation of ethylene biosynthesis

The plant hormone ethylene is involved in many plant processes ranging from seed germination to leaf and flower senescence and fruit ripening. Ethylene is synthesized from methionine, via S-adenosyl-L-methionine (SAM) and 1-amino-cyclopropane-1-carboxylic acid (ACC). The key ethylene biosynthetic enzymes are ACC synthase (ACS) and ACC oxidase (ACO). Manipulation of ethylene biosynthesis by chemicals and gene technology is discussed. Biotechnological modification of ethylene synthesis is a promising method to prevent spoilage of agricultural and horticultural products.     

Dose-dependent effects of malformin A1 on IAA-induced ethylene production in mung bean (Vigna radiate L.) hypocotyl segments

Purified malformin A1 (cyclo-D-Cys-D-Cys-L-Val-D-Leu-L-lle), a cyclicpentapeptide toxin fromAspergillus niger, was applied to the hypocotyl segments of mung bean (Vigna radiata L.) seedlings to investigate its role in regulating ethylene biosynthesis. Production of ethylene was induced by treating the plants with 0.1 mM indole-3-acetic acid (1AA). When 0.1 μM malformin A1 was then applied, ethylene production increased and the activities of two key enzymes for its biosynthesis, 1-aminocyclopropane-1-carboxylic acid (ACC)-synthase (ACS) and ACC-oxidase (ACO), were also stimulated. However, at levels of 1 or 10 μM malformin A1, both ethylene production and enzymatic activities were significantly reduced. In the case of ACO,in vitro activity was regulated by malformin A1, independent of ACS activity or the influence of IAA. Furthermore, the conjugate form of ACC, N-malonyl ACC, was significantly promoted by treatment with 0.1 μM malformin A1. These data suggest that malformin A1 can modulate ethylene production through diverse paths and that its effect depends on the concentration of the treatment administered.     

Developing tools for investigating the multiple roles of ethylene: identification and mapping genes for ethylene biosynthesis and reception in barley

The plant hormone ethylene is important to many plant processes from germination through senescence, including responses to in vitro growth and plant regeneration. Knowledge of the number and function of genes that are involved in ethylene biosynthesis and reception is necessary to determine the role of specific genes within gene families known to influence ethylene biosynthesis and other aspects of ethylene function in plants. Our objective was built on previous studies that have established the critical role of ethylene in the in vitro response of barley (Hordeum vulgare L.), and that have identified ethylene-related QTL in the barley genome. In this study, we have identified the locations of genes in the barley 1-aminocyclopropane-1-carboxylic acid (ACC) synthase (ACS), ACC oxidase (ACO), and ethylene receptor (ETR) gene families. Specific primers for PCR amplification of each gene were developed and used to map these genes in the Oregon Wolf Barley mapping population. Five ACS, 8 ACO, and 7 ETR genes were identified and mapped to six of the barley chromosomes. Gene locations were syntenous to the orthologs in rice except for two that mapped to chromosome 6H. Gene duplication was evident for ACO genes on chromosomes 5H and 6H. Gene-specific primers will be useful for determining expression of each gene under various environmental conditions, including in vitro environments, to better understand the role of ethylene. Of the six known QTL for green plant regeneration in barley, three were located near the genes mapped in this study.     

No difference in the regulation pattern of calcium on ethylene biosynthesis between wild-type and never-ripe tomato fruit at mature green stage

This work investigated how calcium regulates the ethylene biosynthesis in the fruits of wild-type tomato (Lycopersicon esculentum L.) and their ethylene receptor never-ripe (Nr) mutants. In Nr tomato, the ethylene perception was blocked. When both materials were treated with calcium, the content of 1-aminocyclopropane-1-carboxylic acid (ACC)/malonyl-ACC and the activity of ACC oxidase (ACO) in tomato fruit discs increased, whereas the production of ethylene, content of malondialdehyde, and membrane permeability decreased. Calcium treatment did not affect the activity of ACC synthase, which is the first committed step in the ethylene biosynthesis pathway. The expression of LeACO1 in mature green fruit was inhibited significantly by calcium treatment in wild-type and Nr tomatoes, but the expression of LeACS2, the key ACC synthase gene in ethylene synthesis during tomato fruit maturing, was not affected. These results revealed that the effect of calcium on ethylene biosynthesis in tomato mature green fruit was independent of ethylene perception. The results also revealed that the targeting step of calcium preventing ethylene production was located at the ACC conversion to ethylene, by means of inhibiting ACC availability for ACO through enhancing cell membrane integrity and by means of preventing LeACO1 gene expression. Published in Russian in Fiziologiya Rastenii, 2006, Vol. 53, No. 1, pp. 60–67. The text was submitted by the authors in English.     

Aluminum-induced ethylene production is associated with inhibition of root elongation in Lotus japonicus L

Inhibition of root elongation by toxic aluminum (Al(3+)) occurs rapidly and is one of the most distinct and earliest symptoms of Al toxicity. To elucidate mechanism underlying Al(3+)-induced inhibition of root elongation, we investigated the involvement of ethylene in Al(3+)-induced inhibition of root elongation using the legume model plants Lotus japonicus and Medicago truncatula. Root elongation of L. japonicus and M. truncatula was rapidly inhibited by exposure to AlCl(3). A similar rapid inhibition of root elongation by the ethylene-releasing substance, ethephon, and the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC), was also observed. The Al(3+)-induced inhibition of root elongation was substantially ameliorated in the presence of antagonists of ethylene biosynthesis [Co(2+) and aminoethoxyvinylglycine (AVG)]. Al(3+) increased the activity of ACC oxidase (ACO), and induced a rapid evolution of ethylene from root apices and expression of genes of ACC synthase (ACS) and ACO. These findings suggest that induction of ethylene evolution resulting from up-regulation of ACS and ACO plays a critical role in Al(3+)-induced inhibition of root elongation.     

Exogenous Eethylene influences flower opening of cut roses (Rosa hybrida) by regulating the genes encoding ethylene biosynthesis enzymes

1 Introduction The simple gaseous phytohormone ethylene as apotent modulator has various roles in plant growth,development and in response to biotic and abioticstress, such as germination, fruit ripening, flower andleaf senescence, and responsiveness to pathogen attack and mechanical damage[1]. The opening and senes-cence of many kinds of flowers are correlated tightly to ethylene, including carnation, petunia, orchid and rose[2]. Generally, roses are classified as ethylene-sen-sitive, however…     

Effect of Down-Regulation of Ethylene Biosynthesis on Fruit Flavor Complex in Apple Fruit

The role of ethylene in regulating sugar, acid, texture and volatile components of fruit quality was investigated in transgenic apple fruit modified in their capacity to synthesize endogenous ethylene. Fruit obtained from plants silenced for either ACS (ACC synthase; ACC-1-aminocyclopropane-1-carboxylic acid) or ACO (ACC oxidase), key enzymes responsible for ethylene biosynthesis, expectedly showed reduced autocatalytic ethylene production. Ethylene suppressed fruits were significantly firmer than controls and displayed an increased shelf-life. No significant difference was observed in sugar or acid accumulation suggesting that sugar and acid composition and accumulation is not directly under ethylene control. Interestingly, a significant and dramatic suppression of the synthesis of volatile esters was observed in fruit silenced for ethylene. However, no significant suppression was observed for the aldehyde and alcohol precursors of these esters. Our results indicate that ethylene differentially regulates fruit quality components and the availability of these transgenic apple trees provides a unique resource to define the role of ethylene and other factors that regulate fruit development.     

GhXB38D represses cotton fibre elongation through ubiquitination of ethylene biosynthesis enzymes GhACS4 and GhACO1

Ethylene plays an essential role in the development of cotton fibres. Ethylene biosynthesis in plants is elaborately regulated by the activities of key enzymes, 1-aminocyclopropane-1-carboxylate oxidase (ACO) and 1-aminocyclopropane-1-carboxylate synthase (ACS); however, the potential mechanism of post-translational modification of ACO and ACS to control ethylene synthesis in cotton fibres remains unclear. Here, we identify an E3 ubiquitin ligase, GhXB38D, that regulates ethylene biosynthesis during fibre elongation in cotton. GhXB38D gene is highly expressed in cotton fibres during the rapid elongation stage. Suppressing GhXB38D expression in cotton significantly enhanced fibre elongation and length, accompanied by the up-regulation of genes associated with ethylene signalling and fibre elongation. We demonstrated that GhXB38D interacts with the ethylene biosynthesis enzymes GhACS4 and GhACO1 in elongating fibres and specifically mediates their ubiquitination and degradation. The inhibition of GhXB38D gene expression increased the stability of GhACS4 and GhACO1 proteins in cotton fibres and ovules, resulting in an elevated concentration of ethylene. Our findings highlight the role of GhXB38D as a regulator of ethylene synthesis by ubiquitinating ACS4 and ACO1 proteins and modulating their stability. GhXB38D acts as a negative regulator of fibre elongation and serves as a potential target for enhancing cotton fibre yield and quality through gene editing strategy.     

G-protein-coupled alpha2A-adrenoreceptor agonists differentially alter citrus leaf and fruit abscission by affecting expression of ACC synthase and ACC oxidase

Temporal and spatial expression patterns of genes encoding 1-aminocyclopropane-1-carboxylate (ACC) synthase (ACS1 and ACS2) and ACC oxidase (ACO), ACC concentration, and ethylene production in leaves and fruit of 'Valencia' orange (Citrus sinensis [L.] Osbeck) were examined in relation to differential abscission after treatment with 2-chloroethylphosphonic acid (ethephon) alone or in combination with guanfacine or clonidine, two G-protein-coupled alpha(2A)-adrenoreceptor selective agonists. Guanfacine and clonidine markedly reduced ethephon-enhanced leaf abscission, but had little effect on ethephon-enhanced fruit loosening. Ethephon-enhanced fruit and leaf ethylene production, and ACC concentration in fruit abscission zones, fruit peel, leaf abscission zones, and leaf blades were decreased by guanfacine. Guanfacine reduced ethephon-enhanced expression of ACS1 and ACO genes in leaf abscission zones and blades, but to a lesser extent in fruit abscission zones. The expression pattern of the ACS2 gene, however, was not associated with abscission. The results demonstrate that differential expression of ACS1 and ACO genes is associated with reduction of ethephon-enhanced leaf abscission by guanfacine, and suggest a link between G-protein-related signalling and abscission.     

Regulation of the protein and gene expressions of ethylene biosynthesis enzymes under different temperature during peach fruit ripening

Ethylene has profound effect on fruit development and ripening, and the role of ethylene biosynthesis enzymes involving 1-aminocyclopropane-1-carboxylic acid (ACC) synthase (ACS), ACC oxidase (ACO), and S-Adenosyl-l-methionine synthetase (SAMS) in peach fruit (cv. Xiahui-8) was characterized under 25 and 4 °C, respectively. All these enzymes in ethylene synthesis pathway were identified using 2-DE and real-time PCR. Both protein and gene expressions of ACO and SAMS were much higher at 25 °C than at 4 °C. Among five members of ACS family, PpaACS4 may belong to system II ethylene biosynthesis, while PpaACS3 involved in system I during development stage, and low temperature can induce PpaACS1 expression. The ethylene release and low expressions of proteins and genes of most enzymes indicated that low temperature can effectively postpone ripening stage by reducing ethylene evolution. High gene expression of PpaSAMS did not cause excessive expression of SAMS protein under low temperature, and over-expression of PpaACS1 at low temperature still did not induce increase of ethylene production. The mechanism underlying the phenomenon about how temperature affects ethylene release was also discussed.     

Involvement of ethylene biosynthesis and perception in the susceptibility of citrus fruits to Penicillium digitatum infection and the accumulation of defence-related mRNAs

Citrus fruits infected with the fungus Penicillium digitatum substantially increase the production of the plant hormone ethylene. In this study, the regulation of ethylene biosynthesis in Citrus sinensis-infected fruits and its putative involvement in an active defence response against P. digitatum infection is examined. Ethylene production is demonstrated as being the result of the co-ordinated and differential up-regulation of at least three ethylene biosynthetic genes: ACS1, ACS2, and ACO. Blocking ethylene perception by 1-MCP resulted in an increased ethylene production and ACS2 expression during infection and mechanical wounding, suggesting that this gene is negatively regulated by ethylene. ACO expression was induced by ethylene in the absence of wounding or infection, although further results indicate that its induction during the course of infection may not be primarily mediated by ethylene. Treatment with 1-MCP also increased susceptibility to Penicillium decay, showing an involvement of ethylene perception in promoting defence responses in citrus fruits. The changes in the expression of two defence-related genes up-regulated during infection were also studied: the ones coding for phenylalanine ammonia-lyase (PAL) and an acidic class II chitinase (ACR311). The onset of PAL expression after mechanical wounding or inoculation was not changed in 1-MCP-pretreated fruits, while its later increase during the course of infection was abolished. Chitinase gene induction was more related to mechanical damage and was partially repressed by ethylene. These studies indicate distinct possible regulatory mechanisms of plant fruit defence genes in the context of fungal infection and ethylene perception.