Abstract: Germination is the first and maybe the foremost growth stage in the life cycle of a plant. Herein, we report that initiation of germination in the Arabidopsis Columbia ecotype was accompanied by a sharp decrease in the amount of extractable total RNA. At the beginning of our germination experiment, we were usually able to obtain 35–40 µg total RNA from 100 mg dry seeds. However, after 3 d of cold stratification, we could only obtain less than 5 µg total RNA from the same amount of starting material. Young seedlings contained approximately 100 µg total RNA per 100 mg fresh tissue. Further studies showed that inhibition of de novo RNA synthesis by actinomycin D prevented the degradation of parental RNA and, in the meantime, significantly delayed the germination process. Several ribonuclease-like genes that were highly expressed in dry seeds, and especially during the cold stratification period, were discovered. We propose that these enzymes are involved in the regulation of parental RNA degradation. These results indicate that parental RNA metabolism may be an important process for Arabidopsis seed germination.(Author for correspondence.E-mail:zhuyx@water.pku.edu.cn)

Key words: actinomycin D, degradation, parental RNA, ribonucleases.