Total RNAs were extracted using standard hot phenol RNA preparation method (51 (link)). For RT-PCR analysis, 1.5 µg of total RNAs were subjected to reverse transcription (RT) using gene-specific primers, and then the resulting cDNAs were analysed by standard PCR method or qPCR. Primers used are listed in Supplementary Table S3. The half-life of pre-mRNAs was determined as described previously (52 (link),53 (link)). For northern blotting, the procedures were as previously described (50 (link)) except that total RNAs (10 µg) were separated by 6% acrylamide gels. Sequences of oligonucleotide probes are listed in Supplementary Table S3. Band intensities were quantified using ImageJ densitometry software.