单半乳糖甘油二脂缺失对烟草光合特性的影响

Photosynthetic Characteristics of a Tobacco Mutant Deficient in the Monogalactosyldiacylglycerol

以单半乳糖甘油二脂(MGDG)相对含量比野生烟草显著降低的突变体(M18)及野生型烟草为材料,通过对转基因烟草叶绿体类囊体膜的低温荧光、放氧活性以及叶片的叶绿素荧光分析,研究MGDG部分缺失对烟草叶片光合特性的影响。结果表明,在低温下(77K)MGDG部分缺失并不影响烟草叶绿素荧光发射峰(F683和F730)的位置,但使光系统Ⅱ(PSⅡ)及光系统Ⅰ(PSⅠ)的荧光发射峰的强度减弱,F683/F730比值降低,直接影响激发能在PSⅡ和PSⅠ之间的均衡分配,使叶绿素a和叶绿素b之间的能量传递受阻,降低光能转化效率;MGDG部分缺失使PSⅡ放氧活性下降了72.9%;转基因烟草叶绿素荧光参数中最大光化学效率(Fv/Fm)、暗适应最大荧光(Fm)、实际光化学效率(Yield)、光化学猝灭系数(qP)比野生型烟草分别降低了7%、49%、32%和18%,并以Fm降幅最大。研究证明,MGDG在维持植物叶绿体类囊体膜的功能,特别是PSⅡ的功能方面起着重要的作用。

Monogalactosyldiacylglycerol is the major structural component of thylakoid membrane in higher plants,and it is considered to play an important role in the structural organization of thylakoid membranes.Here we used transgenic tobacco（M18） which content of MGDG greatly reduced and wild type tobacco（WT） as material to study if the deficiency of the MGDG would affect photosynthetic characteristics of tobacco leaves.In this paper,we measured the low temperature（77K） fluorescence spectrum and oxygen-evolving activity of thylakoid membranes and chlorophyll fluorescence parameters of leaves in M18 and WT tobaccos.The 77K influorescence spectrum shows that the deficiency of the MGDG does not affect the position of the fluorescence emission apex（F683 and F730） but just reduce their intensity of the PSⅡ and PSⅠ.From the decrease of the ratio of F683/F730,we know deficiency of the MGDG may directly affect the balanced distribution of the excited energy between PSⅡ and PSⅠ,hinder the energy transportation between chlorophyll a and b,and decrease the transformation efficiency of light energy.Lack of the MGDG leads to that photosynthetic oxygen evolution in thylakoid organization of M18 was severely fallen by 72.9% compared with WT tobacco.Chlorophyll fluorescence parameters,Fv/Fm,Fm,Yield and qP fall 7%,49%,32% and 18%,respectively in M18 compared with WT.All of these proved MGDG playing an important role in the photosynthesis of thylakoid,especially in the function of PSⅡ.