H. Kobayashi et al., DNA synthesis and fragmentation in bacteroids during Astragalus sinicus root nodule development, BIOS BIOT B, 65(3), 2001, pp. 510-515
Histo- and cytochemical techniques were used to study the DNA replication a
nd fragmentation patterns in bacteroids formed by Mesorhizobium huakuii sub
sp, rengei in nodules of Astragalus sinicus. DNA replication was detected b
y the incorporation of 5-bromo deoxy-uridine, Signals denoting DIVA synthes
is were observed in plant nuclei within the nodule meristem and in bacteroi
ds near the meristem. The TUNEL (TdT-mediated dUTP nick-end labeling) assay
was used to measure DNA fragmentation. In nutrient-depleted 2-mpi (month(s
) post inoculation) nodule sections, some bacteroids were in vacuoles, and
DNA fragmentation signals were observed only in such bacteroids, In contras
t, 1-mpi nodule sections without nutrient depletion showed neither bacteroi
d localization in vacuoles nor DNA fragmentation signals. The bacteroid tra
nslocation into vacuoles upon nutrient starvation might results from autoph
agy of the plant. In 2-mpi nodule sections, bacteroids with DNA fragmentati
on signals appeared within the cytoplasm of some nodule cells in the senesc
ence zone.