Scientific Papers Series B Horticulture

the shelf life of the fruit for consumers (Opiyoand Ying, 2005).Even if in the past appearance quality has beenemphasized, consumers buy tomatoes on thebasis of appearance and firmness, theirsatisfaction and repeat purchases depend upongood flavor quality (Kader, 1986).MATERIALS AND METHODSA literature search strategy was used, mainlyon the most recent scientific papers on therelationship between ethylene and fruit qualityof tomato, especially during post harvest, usingonline database Science Direct.RESULTS AND DISCUSSIONSGENERAL ASPECTS OF ETHYLENEBIOSYNTHESIS MANAGEMENTDURING FRUIT RIPENINGFruit ripening has received considerableattention due to its commercial importance(Yokotani et al., 2009).The control of fruitsripening is often achieved through earlyharvest, by controlling the postharvest storageatmosphere and by genetic selection for slow orlate ripening varieties (Oms-Oliu et al., 2011).It is know that ethylene function to promotemany aspects of ripening of many climactericfruits, including tomato (Abeles et al., 1992;Yokotani et al., 2009; Barry and Giovannoni,2007) and modulating its levels in thetransgenic plants, as regard as many biotic orabiotic stress factor is readily attainable for avariety of plants [(Stearns and Glick, 2003).Ethylene biosynthesis starts from methioninevia S-adenosyl-L-methionine (AdoMet) havingas an intermediate the non-protein amino acid1-aminocyclopropane-1-carboxylic acid (ACC)(Adams and Yang, 1979). The conversion ofAdoMet to ACC and of ACC to ethylene isassured by ACC synthase and ACC oxidase,respectively (Kende, 1993).Ethylene regulation in climacteric and nonclimactericfruits is under control of twodistinct ethylene producing system defined byMcMurchie et al. (1972): system1(autoinhibitory) and system 2 (autocatalytic).System 1 control the low ethylene productionrate and represent basal ethylene in unripe fruitand vegetative tissues, while system 2 isassociated with the autocatalytic rise in424ethylene production as is the case of matureclimacteric fruits, too (Oetiker and Yang,1995). Fruit ripening and the role of ethylene inits regulation is complex. Therefore,understanding what controls these processes innon climacteric ripening may prove pertinent togaining full understanding of climacteric fruitripening and vice versa (Alexander andGrierson, 2002).Recently, Yokotani et al. (2009) proposed amodel to explain the transition from system 1to system 2. System 1 is produced viaLeACS1A and LeACS6, which are regulated bya negative feedback system, in the case ofabsence of exogenous ethylene and stress, viathe limited expression of LeACS2 and LeACS4,thus registering a limited increase of ethylenebiosynthesis. In a such situation, limitedethylene would play a role as a trigger tostimulate an ethylene burst due to the ethylenedependentexpression of LeACS2 and LeACS4,inducing fruit ripening. System 1 decreaseswith the onset of system 2, as LeACS6 isregulated by a negative feedback system;therefore, system 2 in tomato fruit consists ofboth ethylene-dependent (autocatalytic) andethylene-independent (non-autocatalytic)systems. Even when the effect of system 1ethylene is eliminated, fruit can initiate system2, leading to fruit ripening.Moreover, responses to this hormone is realizedby a signal transduction pathway in whichEthylene Responsive Element Binding Proteins(EREBPs) are transcription factors that helpregulate the ethylene response by regulatingtranscription and gene expression. For example,Zhang et al. (2012) have cloned the geneTomato LeERF1, indicated its location at thecellular level in the nucleus, nucleolus andplastids, and little signal was detected in thecell wall and vacuole. They have establishedrelationship of LeERF1 with the ripening oftomato fruit.MEANS TO EXTEND TOMATO SHELFLIFEMaximum loss in quality and quantity oftomato occurs from harvesting to consumption(Kader, 1986), so, the problem of loss can becontrolled by adapting suitable scientificmethods of packing and storage and byestablishment proper post harvest management(Rahman et al., 2010).