Application of rice ( Oryza sativa   L.) suspension culture in studying senescence in vitro (II). Changes in DNA integrity

Changes in the DNA content and organisation of senescing rice cell cultures (Taipei 309) were studied, using PCR and Southern blot analyses. A mitochondrial gene (coxII), a plastid gene (psaA) and a nuclear DNA maker (RG64) were analysed. The amplification of mitochondrial (mt), plastid and nuclear DNA produced the expected fragments, indicating that there were still some intact organelles and nuclei in the senescing rice cells. However, in plastid and nuclear DNA, changes in the number and size of the PCR products were observed. Southern blot analysis revealed that mt and nuclear DNA contents declined, but plastid DNA content remained relatively the same throughout the senescence.