Study On The Function And Mechanism Of FvMRLKs Receptor-like Protein Kinase In Strawberry Fruit Development

The mechanism study on fruit development and ripening is one of the most important questions in fruit tree science.However,the mechanism of fruit development and ripening has been studied mostly from physiology and biochemical level for many years.The information is little about the mechanism of signal transduction on manipulating of fruit physiological,biochemical metabolism.Malectin-like domain-containing receptor-like kinases(MRLK)family belongs to the family of receptor-like kinases and is widely present in the plant community.Because the Malectin domain is capable of specifically binding oligosaccharides,it is speculated that MRLKs may be closely related to oligosaccharide signal transduction.The cell wall metabolism and oligosaccharide signal transduction are inevitable in fruit development and maturation,so it is speculated that MRLKs may play an important role in fruit development and maturation regulation.In this study,the strawberry which is non-respiration climacteric fruit was used as material,and the role of MRLKs in fruit development and ripening regulation was studied.The main results are as follows:1.Based on bioinformatics analysis,we identified 62 FvMRLKs in the strawberry genome,which were named FvMRLK1-FvMRLK62 according to its distribution on the chromosome.These genes were classified into six subfamilies with distinct malectin domains in the extracellular regions of the encoded proteins.The analysis the intron,exons,Malectin conserved domain and biological genetic evolution showed that the same family in genetic evolution has similar structural features,and similar structures determine similar functions.2.Gene expression profiles showed that members of the FvMRLK family were expressed in various tissues such as roots,stems,leaves and fruits,but the expression levels in the roots were higher than those in other organs.Among them,33 members of the FvMRLK family were specifically expressed in the fruit.Interestingly,the gene expression characteristics of over 60%of the 33 members is closely related with fruit development and ripening process.The expression level is very high in the early stages of fruit development,however,the expression level dropped sharply with the fruit mature.Most of the FvMRLK family can respond to internal and external factors(such as hormones and environmental)that manipulated the development and ripening of strawberry fruit.These results indicated that FvMRLKs may play an important role in regulating the fruit development and ripening of strawberry.3.In order to prove the role of MRKLK family in regulating strawberry fruit development and ripening,FaLK47,a member of the FaMRLK family,was studied by strawberry fruit transient transgenic technology.The results showed that the over-expression of FaMRLK47 could significantly inhibit the ripening of strawberry fruit.On the contrary,FaMRKL47-RNAi could promote strawberry fruit ripening.Correspondingly,FaMRLK47-OE could inhibit the expression of a series of fruit ripening genes,however,FaMRLK47-RNAi could promote that.The results provided a direct evidence that the FaMRLK family participates in regulating strawberry fruit development and ripening.4.In view of the FaMRLK family plays an important role in regulating the development and ripening of strawberry,the oligosaccharide signal is further studied in regulating the fruit development and ripening in strawberry.The isolation and analysis system of oligosaccharides was successfully established in strawberry fruit.It was proved that oligosaccharides could play an important role in strawberry fruit development and ripening.In order to further study the molecular recognition of FaMRKL family,the expression and purification system of FaMRLK47 was established.The isothermal titration microcalorimetry analysis confirmed that FaMRLK47 could recognise oligosaccharide signals.The study provided an important basis for further analysis of FaMRLKs signal transduction mechanism.In summary,MRLKs were found to play an important role in regulating the fruit development and ripening in strawberry.FaMRLKs in regulating of fruit development and ripening may be closely related to the recognition and transduction of oligosaccharide signal.The study not only provided important information for further analysis of strawberry fruit development and ripening mechanism,but also played an important role in the future breeding and quality improvement.