Fig. 2.

Identification of genes co-regulated by BRs and ABA in publicly available microarray data. (A) Venn diagram of ABA- and BR-responsive genes. Genes that are antagonistically regulated by these hormones were selected from previously-reported data sets (Nemhauser et al., 2006). Left, Venn diagram of genes downregulated by BRs but upregulated by ABA; right, genes upregulated by BRs but downregulated by ABA. Fisher’s exact test was conducted to determine the p-value of overlapping genes (P < 0.09 for genes upregulated by ABA and downregulated by BR; P < 0.0051 for genes downregulated by ABA and upregulated by BR). (B) Enrichment of the BR-response element (BRRE) in the -1000 bp promoter sequences of 62 and 50 genes co-regulated by BRs and ABA, respectively. The percentage of genes that harbor at least one BRRE (CGTG[T/C][G/A]) was determined by searching the Arabidopsis genome sequence database. (C) Time-course analysis of RD26 and ANAC102 transcript levels in seven-day-old wild-type seedlings treated with 1 μM epi-BL or 50 μM ABA in liquid MS media. Results were normalized using UBQ10, and converted to values relative to a mock-treated control. Data are mean ± standard deviation of three technical replicates. (D) RD26 belongs to the NAC transcription factor family, which is composed of at least 94 members (Christianson et al., 2010). Of the entire phylogenetic tree of this gene family, a clade containing RD26 is shown. The length of the bar indicates the number of changes in amino acid residues per unit length of the horizontal branches. (E) qRT-PCR analysis of the expression of ANAC genes clustered with RD26 in (D). UBQ10 levels were used as loading controls. Besides ANAC081, all tested ANAC genes responded similarly to RD26; i.e., they were upregulated in response to ABA, and downregulated after exposure to epi-BL.