Effect Of Nitric Oxide On γ-aminobutyric Acid Shunt Of Tea Plant Under Low Temperature

Tea plant[Camelliia sinensis(L.)O.Kuntze]is an important perennial economic crop in China,and its quality is closely related to the growing environment.Low temperature has a great influence on the growth of tea plants and the quality of tea.Previous studies have shown that nitric oxide(NO)can alleviate the damage caused by various abiotic stresses such as drought,salinity,high temperature,low temperature,heavy metals and radiation stress.In this research,tea plant cultivars ’Baiyeyihao’under low temperature conditions(4℃)were treated with the following treatments:SNAP,PTIO and L-NNA.In addition,low temperature treatment as control group.Root samples were collected at Oh,12h,24h and 48h after treatments.The contents of polyamine,y-aminobutyric acid(GABA),proline(Pro),and metabolism-related enzyme activity,gene expression levels were measured to study the effects of NO on polyamines,GABA and Pro metabolismin tea plants under low temperature stress.The specific research contents and experimental results are as follows:1.The samples were measured for the activities of arginine decarboxylase(ADC),ornithine decarboxylase(ODC),nitric oxide synthase and the contents of spermine(Spm),spermidine(Spd),and putrescine(Put).The results showed that SNAP could promote ODC activity and increase Spm content,while PTIO and L-NNA could inhibit NOS activity and ODC activity.It was also found that exogenous NO promotes polyamine accumulation by regulating the activity of ADC and ODC.2.The samples were measured for the activities of GAD,GABA-T,PDH and P5CS and the contents of GABA and proline.The results showed that SNAP could promote GAD and P5CS activities and increase Pro content at 0-24 h,while PTIO and L-NNA could inhibit GAD activity and GABA-T activity.Studies also have found that exogenous NO can promote Pro accumulation by regulating GAD,GABA-T and P5CS activities.3.The expression levels of the enzyme genes related to the polyamine,GABA,and Pro metabolic thways were mesured and analyzed.4.The results showed that NO promoted the expression levels of CsADC,CsODC,CsSPMS,CsGABA-T,CsADC and CsSPMS genes,while CsGAD and CsP5CS genes was inhibited after the application of exogenous NO.The expression of CsADC and CsSPMS was about 2.9 times comred with control group.These results indicated that exogenous NO can regulate genes expression of enzymes involved in tea plant polyamine,GABA,and proline metabolic thways under low temperature stress.In conclusion,NO promotes an increase in polyamines and Pro contents by regulating the activities of ADC,ODC,NOS,GAD,GABA-T,P5CS and the expression of CsADC,CsODC,CsSPMS,CsGABA-T,CsGAD and CsP5CS genes under low temperature stress.