Figure 4.

kn1 and PIN1a~YFP Accumulation Patterns Are Normal in the blk1-R SAM but Are Aberrant in the Mutant Tassel Primordia.

(A), (B), (E), and (F) RNA in situ hybridizations with kn1 probe. wt, wild type.

(C), (D), (G), and (H) Confocal images of PIN1a~YFP fluorescence.

(A) kn1 mRNA accumulates in the indeterminate cells that make up the SAM proper but is downregulated at the P0 of wild-type 21-DAG seedlings.

(B) Mutant SAMs at 21-DAG have normal kn1 expression patterns, but mRNA levels are reduced.

(C) Wild-type SAMs at 21 DAG show PIN1a upregulation at the P0.

(D) blk1-R SAMs at 21 DAG have normal PIN1a upregulation at the P0.

(E) In wild-type tassel primordia, kn1 mRNA accumulates at the apices of branch primordia, at the apex of central tassel spike, at the presumptive sites of SPM initiation (arrow), and within developing SPMs.

(F) kn1 accumulation in blk1-R tassel primordia is reduced, and normal upregulation does not occur along the flanks of the inflorescence.

(G) PIN1a~YFP is upregulated in SPMs and along the flanks of the wild-type tassel primordium where it marks the initiation of bract primordia (br).

(H) PIN1a~YFP localization is aberrant in blk1-R mutant tassel primordia, which may account for the large reduction in SPM number. bm, branch meristem.