Study On The Physiological Mechanism Of Xanthine Dehydrogenase Delaying Rice Senescence Under Stress

In order to analyze the physiological mechanism of xanthine dehydrogenase delaying the senescence of rice in abiotic stress,with the japonica rice cultivar of Nipponbare as receptor variety of OsXDH over expression(OE)and interference(Ri)of T3 generation homozygous lines and wild type(WT),salt,high-temperature,darkness and drought stress were performed at seedling stage.The physiological and biochemical charact including chlorophyll,the kinetic parameters of fluorescence,chlorophyll content,soluble protein content,protective enzyme activity,MDA content,ureides content and XDH enzyme activity were respectively mensurated before the stress,after stress and 7 days return to normal growth,and the main results are as follows:1.The XDH enzyme activity of OE line was greater than the wild type and Ri line,while it was lowest in the Ri line in before the stress,after stress and 7 days return to normal growth.The qP of the over expression lines changed little,and the NPQ decreased,but they were contrary in the Ri line.The chlorophyll content and the contents of soluble protein of OE line was greater than the WT and Ri line.During the stress period,the activity of SOD increased of the OE,WT and Ri line,and it is little difference among the three.However,during the period of recovering normal growth,the decrease of SOD activity in over expression lines was less than the WT and Ri line.The POD activity of the OE line increased during the stress period,the WT and Ri line reduce,and during the recovery period all of the three were reduced,but its decrease scope in over expression was less than the WT and Ri line.During the stress the CAT activity reduction of the OE line was less than the WT and Ri line,while its increase was greater than the WT and Ri line during the recovery period.During the stress the MDA content of the OE line increased slightly,and it was less than the WT and Ri line.The allantoin content of the OE,WT and Ri line are increased rapidly in stress,but the OE line increased slightly larger than the WT and Ri line,and there is no different in the allantoate content.During the recovery period,the allantoin content of the OE line continued to increase,while the WT and the Ri line began to decline,but the allantoate content of the three increase.2.The XDH enzyme activity of OE lines were enhanced,yet the WT increased at first and then decreased,and the XDH activity of the Ri line was decreased in before the stress,after stress and 7 days return to normal growth.The changes of chlorophyll and soluble protein content in each strain were similar to salt stress.During the period of stress and the recovery period,the SOD activity in different lines had different decrease,but the OE line was smaller than that of the WT and Ri line.During the stress period,the POD activity of the OE increased,nevertheless the WT and Ri line decreased.During the the recovery period,the POD activity of the OE line increased significantly,while the WT and the Ri line still fell slightly.During the stress and stress recovery during,the CAT content of the OE line did not change significantly,whereas the WT and Ri line decrease.During the period of stress,the MDA content of the three was increased,but the content of OE lineincreased slightly,and it was lower than the WT and Ri line.The content of allantoin of the OE,WT and Ri line in stress was increased rapidly,but the OE line increased slightly larger than the WT and Ri line,and the allantoate content with allantion have similar change.3.The XDH enzyme activity of OE line and WT have enhanced,while the Ri line increased slightly after the reduction in before the stresses,after stress and 7 days return to normal growth.At the same time,the qP of the OE line increased,and the NPQ decreased,and the Ri line' qP increased slightly,and the NPQ also increased.The decrease of chlorophyll contents in OE line was smaller than the WT and Ri line;the soluble protein content of OE increased,while the WT and Ri line were significantly decreased.The SOD activity of the OE and WT line showed decreased-increased trend,yet the Ri line showed decreased-decreased trend;the POD and CAT activity of the OE line showed decreased-increased trend,yet the interference and WT lines showed decreased-decreased trend.The MDA content of the OE,WT and Ri line showed increased-increased trend and the OE line increased less than the WT and Ri line.Allantoin and allantoate content showed increased-decreased trend of the OE,WT and Ri line during the period of the stress and the recovery period,and the OE line increased more than the WT and Ri line.4.The XDH enzyme activity of the OE line had a slight increase after depression and the WT and Ri line were low in before the stresses,after stresses and after stresses for 7days return to normal growth.The qP of the over expression was significantly reduced,and the NPQ was significantly increased,and the qP of the Ri line was significantly decreased,but there is no significant change in NPQ.The decrease of chlorophyll content and soluble protein content in the OE line were less than the WT and Ri line during the period of the stress.The SOD and CAT activity of the over expression,WT and Ri line showed decrease-decrease trend during the period of the stress and the recovery period,but the OE line increased less than the WT and Ri line;The POD activity of the OE line showed decreased-increased trend,while the the WT and the Ri line still decreased.The MDA content of the OE line showed increased-decreased trend,while the WT and the Ri line showed increased-increased trend.The allantoin and allantoate content of the OE,WT and Ri line showed increased-decreased trend during the period of the stress and the recovery period,and OE strains content was always more than the WT and Ri line.In summary,the OsXDH of the OE showed the content of soluble protein and chlorophyll had a higher content,the lower content of MDA,the higher content of the protective enzyme activity and the XDH enzyme activity than the WT and Ri line,and the ureides compounds contents were also higher under the stress,the results indicate that the over expression of OsXDH,enhance the resistance to abiotic stress in rice.