红光对绿豆下胚轴线粒体Ca~(2+)积累、ATPase及NAD激酶活性的影响

绿豆下胚轴切段经红光处理后10min,其线粒体的Ca~(2+)积累下降15％,Ca~(2+)-ATPase 及 Mg~(2+)-ATPase活性也分别下降29％和10％,切段CaM含量增加近1倍。Ca~(2+)存在时,红光能促进线粒体NAD 激酶活性。说明Ca~(2+)-ATPase及一部分Mg~(2+)-ATPase可作为钙泵控制Ca~(2+)进入线粒体。

Effects of Red Light on Calcium Accumulation,Activities of ATPase and NAD Kinase in Mitochondria Isolated from Hypocotyl Segments of Mung Bean

With ~(45) Ca~(2+)-transport assay,the effect of red light (R) on calciumaccumulation in mitochondria isolatedfrom hypocotyl segments of 3-day-oldetiolated seedlings of mung bean(Phaseolus radiatus) was investigated.Immediately after red light irradiation,the active accumulation of Ca~(2+) in mi-tochondria was the same as that fromunirradiated segments. 10 min later,however, the uptake of calcium ion bymitochondria from R-irradiated seg-ments was lowered by 15%. More-over, since calcium accumulation inmitochondria needed energy, the activ-ities of ATPase in mitochondria wereexamined. The results demonstratedthat, 10 min after red light irradia-tion, the activities of Ca~(2+)-ATPaseand Mg~(2+)-ATPase declined by 29%and 10%, respectively. It seemed thatCa~(2+)-ATPase and part of Mg~(2+)-AT-Pase acted as calcium ion pumps regu-lating Ca~(2+) accumulation in mitochon-dria. In addition, CaM content in R-irradiated sgements was 95% higherthan that in the control, when the seg-ments were isolated 10 min after treat-ment. The activity of NAD kinase locat-ed in mitochondria was stimulated byred light when isolated 10 min after ir-radiation and the increase of enzymeactivity reached 17% only when Ca~(2+)(1 mmol/L) was present in the assaymedium. From the data reported here it issuggested that the activities of calciumpumps located in hypocotyl mitochon-dria of mung bean are depressed by redlight irradiation and the accumulationof Ca~(2+) in the mitochondria are de-creased. The concentrations of Ca~(2+)and CaM in the cytosol increased and,as a result, Ca~(2+) (and calmodulin )-de-pendent enzymes such as NAD kinasewhich play an important role in a largenumber of cellular processes are stimu-lated.