Screening For Histone Modifiers (HMs) Involved In Litchi Fruit Abscission And Observation Of PH Values In Cytoplasm Of Abscission Zone

Litchi(Litchi chinensis Sonn.),which originates from China,has important economic and nutritional valueand is very popular in Southern China.However,the litchi tree is easily subject to the southern rainy season which causes serious physiological fruit abscission and heavy economic loss.Thus,addressing this problem is key to promote litchi industry development.Previous transcriptome profiling found a large number of genes involved in litchi fruit abscission,but the molecular mechanism of how these genes are regulated is still unknown.Histone modification,as an important mechanism of epigenetic regulation,play a crucial role in regulating gene transcription.Here,based on the litchi genome database,through homologue searching and using bioinformatics and qRT-PCR to mine the histone modifiers(HMs)candidates involved in litchifruit abscission.In addition,the pH values in cytoplasm of abscission zone was also discussed.The main results were as follows:(1)87 HMs were identified,including 6 histone acetyltransferase(HATs),11 histone acetylation enzyme(HDACs),48 histone methyltransferase(HMTs)and 22 histone methylation enzyme(HDMs).(2)The HMs gene expression under two fruit abscission-promoted treatments was analyzed.It was found that 17 HMs genes showing significant differences.Further analysis showed that these genes displayed four expression patterns in response to fruit abscission: early response pattern,mid-response pattern,late response pattern,and full-stage response pattern.(3)Three prokaryotic expression vectors of histone deacetylase genes were successfully constructed,and the induced proteins showed histone deacetylase activity.(4)Seven genes likely involved in litchi fruit abscission were selected to transform into Arabidospsis and T2 generation transgenic lines have been obtained.(5)The intensity of BCECF green fluorescence signal was enhanced following the fruit abscission,indicating that licthi fruit abscission is likely closely associated with alkalization of the cytosol in abscission zone cells.