Transformation Of Poncirus Trifoliata SnRK2.4 And SnRK2.6 To Lemon,and Analysis Of Polyamine Content And Tolerance Of Transgenic Plants

SnRK2(Sucrose non-fermenting 1-related protein kinase2)is a specific kind of Ser/Thr protein kinase existing in plants.It plays a key role in ABA-signaling pathway and plant stress resistance.However,the function of SnRK2 in regulating the synthesis of polyamines is still unclear.Based on previous researches,two Poncirus trifoliata(L.)Raf SnRK2 genes,namely PtrSnRK2.4 and PtrSnRK2.6,are cloned and agrobacterium-mediated overexpressed in lemon in this research.In addition,the polyamines content and stress tolerance evaluation are investigated in PtrSnRK2.4-overexpressing lines.The results are following:1.PtrSnRK2.4 and PtrSnRK2.6 are cloned from P.trifoliata.The full-length sequence analysis of PtrSnRK2.4 revealed that it has 1026 bp,which encodes 341 amino acids.While PtrSnRK2.6 encompasses 1092 bp that encodes 363 amino acids.The phylogenetic analysis showed that PtrSnRK2.4 and PtrSnRK2.6 belong to Group III and Group II,respectively.2.Agrobacterium-mediated transformation method is used to get transgenic lemon plants.Consequently,24 PtrSnRK2.4-overexpressing transgenic plants and 8 PtrSnRK2.6-overexpressing transgenic plants were obtained.In the transgenic lines,the relative expression level of some related genes were checked.ABF1,ABF2 were significantly up-regulated in both PtrSnRK2.4 and PtrSnRK2.6-overexpressing lines.However,ABF4 is up-regulated to greater degree in the PtrSnRK2.6-overexpressing lines than in the PtrSnRK2.4-overexpressing lines.On the other hand,transcript levels of ADC gene were prominently increased in the transgenic lines overexpressing the two genes relative to the wild type(WT).Meanwhile,the content of putrescine in PtrSnRK2.4 transgenic lines was higher compared to the WT.3.For stress tolerance analysis,PtrSnRK2.4 transgenic and WT plants were dehydrated for 60 min.The results showed that WT leaves displayed more serious wilting phenotype compared to those from transgenic lines.Furthermore,fresh water loss rate and the relative electrolyte leakage in the WT were higher than those of the transgenic plants,implying that the PtrSnRK2.4 could play a positive role in dehydration tolerance.