Fig 1. Phylogeny and expression patterns of KNOX and BELL genes.

(A) Phylogenetic relationships of KNOX and BELL gene families in the plant lineage. Available sequence information suggests the gene duplication producing the KNOX and BELL genes occurred before the divergence of red and green algae. A gene duplication in the lineage leading to land plants created KNOX1 and KNOX2 genes from an ancestral algal KNOX gene. Estimated dates for some nodes are listed in millions of years before present (Mya). (B) In Arabidopsis, KNOX1, KNOX2, and BELL proteins are encoded by 4, 4, and 13 genes, respectively. In addition, KNATM encodes for a KNOX-related protein lacking a homeodomain. Detailed phylogenetic analyses of KNOX genes are presented in S1 and S2 Figs. (C) Schematic depiction of expression patterns for Arabidopsis KNOX1, KNOX2, and BELL genes based on previous literature [75] and publicly available transcriptome data (for details, see S3 and S4 Figs.). KNOX1 and some BELL genes, e.g., PNF and PNY, are primarily expressed in meristematic tissues while KNOX2 and other BELL genes such as SAW1 and SAW2 are expressed in differentiating organs. KNOX2 genes are highlighted in red.