Molecular integrity of chloroplast DNA and mitochondrial DNA in mesophyll and bundle sheath cells of maize.

Abstract

When compared to maize mesophyll cells, the plastid and mitochondrial DNAs in bundle sheath cells are less fragmented, less damaged, and contain fewer DNA polymerase-blocking impediments. Plants that conduct C4 photosynthesis differ from those that employ C3 photosynthesis with respect to leaf anatomy, biochemical pathways, and the proteins and RNA transcripts present in the leaf mesophyll (M) and bundle sheath (BS) cells. Here, we investigate the organellar DNA (orgDNA) from plastids and mitochondria in these two cell types. We use standard qPCR, long PCR, and DNA damage analysis to quantify the amount and quality of orgDNA in isolated M and BS cells of maize. When compared to M cells, BS cells have less orgDNA damage and a higher percentage of unimpeded orgDNA. In addition, the orgDNA is more fragmented in M than BS cells, although orgDNA in BS is subject to more in vitro repair. We suggest that the differences in molecular integrity of orgDNA in these two cells are due to higher levels of reactive oxygen species in M than BS cells.