Abstract
Plant cells retain organellar DNAs in the plastids and mitochondria, in addition to nuclear DNAs. During pollen development, it is known that dramatic decrease of organellar DNAs proceeds in the vegetative cell (differentiating into pollen tube) and generative cell (differentiating into sperms), but the molecular mechanism of organellar DNA degradation is not evident. We previously reported DPD1 (organellar DNA nuclease) that degrades organellar DNAs during pollen maturation. At present, biological significance of the organellar DNA degradation is unclear. To examine the role of DPD1 in more detail, we analyzed transgenic Arabidopsis plants expressing CaMV 35S-DPD1 (overexpressor) or DPD1 pro-GUS. Characterization of these lines implicated that DPD1 is not stably overexpressed in 35S-DPD1 transgenic plants and that DPD1 transcripts accumulate in other tissues besides pollen. Based on these results we hypothesize that DPD1 expression is regulated at post-transcriptional level. Interestingly, our database search detected several microRNAs that potentially target DPD1 transcripts. Characterization of these microRNAs is underway.
