Transcript analysis. We extracted total RNA with the Trizol reagent (Invitrogen). Semiquantitative RT-PCR and RT-Southern blot analysis were done as described elsewhere24. The reaction was terminated after 22 cycles and used rice actin1 as an internal control. Real-time PCR was done as described previously25. All assays were repeated at least three times. Relevant PCR primer sequences are given in Supplementary Tables 4 and 5 online.