Figure 3.

lbl1 encodes an essential component of the ta-siRNA pathway. (A) Diagram of the tas3a transcript. The 21-nt intervals phased relative to the miR390 cleavage site are shown as black brackets and the red brackets indicate the positions of tasiR-ARF. An alignment of tasiR-ARF sequences from maize, rice, and Arabidopsis is shown below, and the green arrow indicates complementarity to the tasiR-ARF LNA probe. Note that tas3d also has complementarity to this probe. (B) RT–PCR showing the relative expression levels of mir390, the tas3 genes, and arf3a in wild-type and lbl1-rgd1 apices. Loading and −RT controls are shown. (C) Small RNA Northern showing that tasiR-ARF accumulates in wild-type, not in lbl1-rgd1 apices. (D) 5′ RACE analysis shows a single prominent arf3a cleavage product (arrowhead) only in wild type. RT–PCR of ubiquitin served as loading control. (E) Diagram of the arf3a transcript with tasiR-ARF complementary sites A and B. The 5′ ends of the tasiR-ARF cleavage products map to complementary site B.