| In order to observe the regulation of two tomato ethylene recepors LeETR1 and LeETR2 on tomato phenotypes,two transformations from tomato(Lycopersicon esculentum) cultivar B1 with constructs containing the antisense sequence from the receiver domain and 3'-untranslated portion of the tomato ethylene receptor LeETR1 and LeETR2 separately under the control of an enhanced cauliflower mosaic virus 35S promoter were obtained by the former work of the group.The transgenic lines ale1 and ale2 and its crossed line dale were identified by PCR,GUS activity determination and PCR for the target genes,all the results were positive.Morphological and physiological changes of the transgenic lines,including growth and development,senescence and abscission,fruit ripening,ethylene binding capacity,were investigated or analyzed in this study.The results were presented as follows:1.The ale1 displayed the following significant characteristics,including shortened adult plant in natural light,epinastic petiole growth,shortened inflorescence stem,delayed anthesis and fruit set, decreased flower number and fruit set percent,and increased abnormality fruits.All of these characteristics suggest that LeETR1 possibly play an important role in regulating tomato vegetative and reproductive growth and development.ale2 only displayed shortened epicoty1,accelerated abscission and slightly epinastic petiole,the phenotype of dale was similar with ale1,which suggest LeETR2 possibly act in limited tissues.2.In fruits,ale1,ale2 and dale showed higher ethylene binding capacity.In leaves,there was no significant difference between the transgenic lines and the control line,which indicates that the ratio of tomato ethylene receptor LeETR1 and LeETR2 expression level is low compared with total level of receptor expression in tomato leaves;ethylene receptor LeETR1 and LeETR2 play an important role in receptor expression in tomato fruits.The ethylene binding capacity of dale was similar with ale1 and ale2,which may indicate that there exists a compensation expression among the receptor gene family.3.ale1 showed an accelerated organ senescence and abscission,and higher sensitivity to ethylene inhibitors.ale2 did not show obvious difference with B1 in flower senescence.dale showed an accelerated petiole abscission than ale1 and ale2,which indicates that LeETR1 and LeETR2 play an important role in negative regulating organ senescence and abscission,they have functionally redundancy,but have different effect degree.4.The individual fruit weight of the transgenic lines was significantly heavier than wild type B1, while the shape of the fruits was much flatter than B1.The firmness,viscosity and elasticity of the transgenic lines were lower than B1(P<0.05) at different stages of ripening.The transgenic lines had a deeper red color compared with B1(P<0.05),but after BK+10,the color of the four lines came to identical.The content of the total soluble solids and relative electrical conductivity of ale1 were significantly higher than ale2,dale and B1(P<0.05).The content of titratable acidity of transgenic lines were much higher than B1(P<0.05).The shelf lives of the transgenic lines were shorter than that of B1. All the results indicate that ethylene receptors differentially regulate fuirts ripening.Besides NR (LeETR3),LeETR1 and LeETR2 may have a close relationship with fruit ripening,and LeETR1 have an obvious regulation effect.5.Through the research it was found that different relation of LeETR1 with LeETR2 possibly exist in different tissue.LeETR1 possibly play a very important role in balancing ethylene response during tomato growth and development.Each member of tomato ethylene receptor family has its unique expression pattern,the loss-of-function or less expression of the receptor would result in obvious spatial and temporal specificity in ethylene responses.Enough evidence has shown that each member of tomato ethylene receptor family do not exist separately,but form an entia including complicated division and cooperation. |
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