生长条件对黄瓜线粒体类质粒稳定性的影响

“津新密刺”等一些黄瓜品种的线粒体中存在主基因组以外的3种环形DNA类质粒pC1、pC2和pC3。改变植株生长的温度、pH或以蔗糖溶液代替无菌水培养黄瓜植株，电泳均能检测到上述3种类质粒。应用ImageMaster VDS系统对各类质粒电泳带的密度进行扫描，通过计算3种类质粒的相对拷贝数及类质粒之间的拷贝数比值，分析不同生长条件对黄瓜类质粒稳定性的影响。结果表明，上述3种培养条件均对黄瓜线粒体类质粒的拷贝数有影响，其影响的程度因类质粒而异，pC3与pC1和pC2相比对环境改变更敏感，提示类质粒间的这种差异可能是类质粒复制方式不同引起的。

INFLUENCE OF GROWTH CONDITIONS ON THE STABILITY OF PLASMID-LIKE DNAS FROM CUCUMBER MITOCHONDRIA

In addition to the main genomic DNAs, there are three kinds of circular plasmid like DNAs, named pC1, pC2 and pC3 respectively, in the mitochondria of some cucumber strains, including JINXINMICI. The seedlings of cucumber were cultivated at different temperature and pH, and in solution with or without sucrose, to investigate the effects of environmental factors on the stability of these plasmid like DNAs. All kinds of plasmid like DNAs were detected in seedlings growing under conditions tested after electrophoretic separation of the mitochondrial DNA. The densities of DNA bands on the negative film were then determined by using the Image Master VDS system and the ratios of their densities to their sizes were used to estimate copy numbers. The results showed that environmental factors influenced differentially the copy numbers of the these plasmid like DNAs, especially of pC3, the smallest plasmid-like DNA, suggesting that these plasmid like DNAs may replicate in different patterns.$$$$