The Metabolic Characteristics And Physiological Regulation Of GABA In Cerasus Sachalinensis Roots Under Waterlogging Stress

Cerasus sachalinensis is widely used in Dalian as a sweet cherry rootstock for its cold resistance,high propagation rate,and adaptability.However it is sensitive to waterlogging because of its shallow roots.In order to understand the characteristics of?-aminobutyric acid?GABA?metabolism and the physiological effect of GABA in cherry roots in responding to waterlogging stress in 72 hours,Cerasus sachalinensis seedlings were used in this study,combinating with the application of GABA,the contents of key metabolites and activities of key enzymes in GABA metabolism and respiratory metabolism,the contents of reactive oxygen species and the activities of antioxidant enzymes were measured under waterlogging stress of seedlings.The main results are as follows:1.Under waterlogging stress,the activity of GABA metabolic branch in the root of Cerasus sachalinensis had been improved.The content of GABA presented an upward tendency which were significantly higher than those of the control;the content of glutamate rose significantly and continuously during the treatment;the waterlogging stress promoted the conversion of Glu to GABA in the root of Cerasus sachalinensis.At the same time,the activity of GABA-T and SSADH increased in the early stage of the treatment,which prompted the catabolism of GABA.Exogenous GABA further promoted the activity of GABA metabolic brach.Compared with waterlogging stress,exogenous GABA significantly promoted the accumulation of endogenous GABA?Glu?SA and Ala content in the Cerasus sachalinensis roots;the activity of GABA-T increased continuously within 24 hours,while the activity of SSADH increased rapidly after 3 hours of the GABA treatment.The conversion of pyruvate to lactate and ethanol was induced,anaerobic respiration rate was induced at the same time.2.The root function of Cerasus sachalinensis was affected under waterlogging stress.The activity and total respiration rate of roots decreased continuously under waterlogging stress and was significantly lower compared with that of the control.The EMP pathway was activated in the early stage of the treatment,while respiration rate of TCA and PPP pathway were inhibited.Exogenous GABA alleviated the damage of waterlogging on the root function of Cerasus sachalinensis.The root activity and total respiration rate increased when the GABA was added,the ATP content of root remained stable at the later stage of the treatment;EMP activity was further activated,its respiration rate increased and the sucrose?fructose and glucose contents were higher than that of waterlogging treatment,the key enzyme activities in this pathway also increased.Exogenous GABA alleviated the inhibition of TCA pathway,the respiratory rate was higher compared with that of the waterlogging stress;the contents of?-KGA?SA and FA accumulated further;the activity of ICDH increased significantly in the later stage of treatment,and the inhibition of SDH and MDH activity were relieved.Exogenous GABA improved the activity of PPP pathway,its respiratory rate and key enzymes activities increased significantly.The accumulation of pyruvate was significant,and the PDC?ADH?LDH activity were significantly higher than that of waterlogging treatment.3.The reactive oxygen metabolism was affected under waterlogging stress.The content of O₂.^-in the leaves of Cerasus sachalinensis increased significantly within 6 hours after waterlogging treatment,and the H₂O₂ content increased significantly after 9 hours of the treatment,MDA also accumulated in the later stage of the treatment;O₂.^-?H₂O₂ and MDA content kept increased during the treatment.The content of ascorbic acid and free proline in leaves and roots increased at the later stage of the treatment;in addition the antioxidant enzyme SOD?CAT?POD and APX activities were significantly increased.Exogenous GABA can further promoted the activities of antioxidant enzymes,and the contents of ascorbic acid and free proline were higher than waterlogging stress,exogenous GABA improved ability to scavenge reactive oxygen of Cerasus sachalinensis.