Synergistic Regulation Of Phytohormones In Strawberry Fruit Development And Ripening

Plant growth and development is controlled by the hormones which regulate different process in plants also control the plant cellular mechanisms and metabolism.These hormones are responsible for making what a plant appears to be,controlling all the process from seed germination to seed formation.From all these aspect one aspect is fruit which is of very much important food source and of great economic value.The occurrence of fruit ripening is not only controlled by one hormone or restricted to one specific stage of development,but a complex network of more than one hormone contribute to various aspect of fruit development and ripening as ripening is a complex process and involves several physiological and chemical changes,such as colour,flavour,texture,and aroma.Strawberry is an important fruit crop and also a model plant for plant biologist.In the past years,hormones regulation of strawberry fruit development and ripening has been increasingly studied.Among the hormones studied,auxin(IAA),abscisic acid(ABA),brassinosteroid(BR)and jasmonic acid(JA)ethylene(ET)all have been suggested to play a role in strawberry fruit development and ripening.However,until now,little information is available about their relative importance and how these hormones could synergistically regulate strawberry fruit development and ripening.In this study,by using a series of physiological and molecular techniques,the mechanism for the synergistic action of the hormones have been studied.The major results and conclusions are as follows:by using pharmacological method,the relative importance of the hormones was evaluated.Both injection and spraying methods suggested that IAA and JA play an important role is strawberry fruit ripening,with IAA and JA respectively function as negative and positive signal to regulate strawberry fruit ripening.Surprisingly,no matter injection and spraying application,ABA was not found to affect fruit ripening.To provide further evidences,a novel method,designated as pressure feeding method,has been successfully developed.By using this method,it was found that ABA may play a role in strawberry fruit ripening.ABA from the pressure inoculation method show enhance in ripening as by this method the hormones initially transferred to the achenes and thus it is proposed that the ABA,regulate the auxin with in the achenes by reducing its effect which trigger the ripening of receptacle in strawberry,by inducing an increase in anthocyanin.These results appeared to suggest the regulation of strawberry fruit ripening by ABA is not a direct action,possibly,ABA functions to regulate the ripening of achenes rather than receptacle,i.e.it was due to the inhibition of IAA transport from achenes to receptacle by ABA that fruit ripening was regulated.To examine the cross-talks among the hormones,the responses of strawberry fruits,in terms of gene expression to hormone as well as light stimulation,was studied by using pressure feeding method.The results showed that light play an important role in the development of anthocyanin content,whereas ABA and light can synergistically trigger pigment development in strawberry.Light and ABA increase the transcription of MYB10,a major gene controlling anthocyanin metabolism.Further studies suggested that JA plays an important roles in the regulation of a series of ripening related genes,such as DFR,PAL1,GST,UFGT,F3H,CHI,CHS,PL,PE,PG,EG1,Cell,XTH1 and so on.Additionally,application of jasmonic acid was found to enhance the expression of Jasmonic acid biosynthesis-related genes,such as AOS,LOS and OPR.To provide more direct evidences,the role of JA was investigated by transient gene manipulation.Application of jasmonic acid enhance the Jasmonic acid biosynthesis gene like AOS,LOS and OPR causing effect on signal pathway genes JMT,COIl.Jasmonic acid key pathway gene FaAOS RNA interference when injected in to the strawberry fruit produce un-colour phenotype.And the overexpression of FaCOIl enhances the ripening process;also induce an increase in expression of plant ripening related gene.It is concluded that the JA,IAA,ABA and Light,paly a synergistic role in strawberry fruit development and ripening.