Sistance to B. cinerea in A. annua.and peaked within 1 h after MeJA treatment, followed by a gradually decline (Calcitonin (salmon) Figure 3A). The treatment with ethephon shows a similar expression pattern with the treatment of MeJA (Figure 3B). The transcript level of AaERF1 was also sensitive to stress treatments. Wounding could induce a significant accumulation of AaERF1 transcript in a short time period (0.5 h). Then the transcript level was quickly decreased (Figure 3C). The statistics analysis showed that the observed differences were statistically significant.Comparative and Bioinformatic Analyses of AaERFThe results of the BLAST-Protein (BLASTP) online (http:// www.ncbi.nlm.gov/blast) showed that the AaERF1 protein had a highly conserved AP2 
domain with other ERF proteins, including Arabidopsis AtERF1, AtERF2, ORCA3, LeERF1, NtERF1, TaERF3 and ORA59 (Figure S2A). This domain is divided into two conserved segments of YRG and RAYG, in which a b-sheet and a-helix are predicted (b-a motif; see Figure S2A). A phylogenetic tree of ERF proteins was drawn using the CLUSTAL X program. The phylogenetic tree demonstrated that ERF proteins originated from a common ancestor and diverged into several groups (Figure S2B). According to the phylogenetic tree, the protein of AaERF1 had close evolutionary relationships to AtERF2, LeERF1, NtERF1 and TaERF3 which showed that they might share similar functions in disease resistance (Figure S2B).Results AaERF1 is Ubiquitously Expressed in A. annuaThe promoter sequence of AaERF1(JQ513909)was cloned by genomic walking (Figure 1A). To observe the expression pattern of AaERF1 in details, the AaERF1 promoter was subcloned to the pCAMBIA1391Z vector (Figure 1B) and then AaERF1 promoterGUS transgenic A. annua plants were generated. Six lines of the transgenic A. annua plants expressing the GUS and three lines for the wild-type background were prepared. All the lines 
showed similar fusion protein expression. GUS activity was detected in all tissues examined, including roots, stems, leaves and flowers (Figure 2A, 2B, 2C and 2D). In 1-month-old plants, GUS activity was high in root tips, stems and leaves (Figure 2A, 2B and 2C). During the flowering period, GUS activity was also detected in flower buds. So, AaERF1 is ubiquitously expressed in A. annua. From Figure 2B and 2C, GUS expression was 10457188 also detected in the glandular trichomes and T-shaped trichomes. No signals were observed in the negative control plants transformed with pCAMBIA1391 empty vector (Figure S1).AaERF1 Protein Interacts with the GCC Box in vitroSince the AP2 domain of AaERF1 contained the key amino acids to bind the GCC box, the recombinant MBP-AaERF1 protein was constructed and overexpressed in E. coli BL21, purified, and used to examine the DNA binding ability in vitro. The purified MBP-AaERF1 protein was mixed, respectively, with the labeled wild-type GCC probe or a GW-0742 site mutated GCC probe in the binding reaction. The results of EMSA showed that the gel mobility shift was specific to the MBP-AaERF1 protein with the labeled GCC probe (lane 2 in Figure 4A). As expected, there were no shifted bands in the combination of MBP-AaERF1 plus the mutated GCC (mGCC) probe (lane 5 in Figure 4A) and in the negative controls, including MBP with the labeled GCC probe (lane 1) or mGCC probe (lane 4), and only the labeled GCC probe (lane 3) or mGCC probe (lane 6) (Figure 4A). The results demonstrated that AaERF1 was able to bind to the GCC box cisacting element, but not to the mut.Sistance to B. cinerea in A. annua.and peaked within 1 h after MeJA treatment, followed by a gradually decline (Figure 3A). The treatment with ethephon shows a similar expression pattern with the treatment of MeJA (Figure 3B). The transcript level of AaERF1 was also sensitive to stress treatments. Wounding could induce a significant accumulation of AaERF1 transcript in a short time period (0.5 h). Then the transcript level was quickly decreased (Figure 3C). The statistics analysis showed that the observed differences were statistically significant.Comparative and Bioinformatic Analyses of AaERFThe results of the BLAST-Protein (BLASTP) online (http:// www.ncbi.nlm.gov/blast) showed that the AaERF1 protein had a highly conserved AP2 domain with other ERF proteins, including Arabidopsis AtERF1, AtERF2, ORCA3, LeERF1, NtERF1, TaERF3 and ORA59 (Figure S2A). This domain is divided into two conserved segments of YRG and RAYG, in which a b-sheet and a-helix are predicted (b-a motif; see Figure S2A). A phylogenetic tree of ERF proteins was drawn using the CLUSTAL X program. The phylogenetic tree demonstrated that ERF proteins originated from a common ancestor and diverged into several groups (Figure S2B). According to the phylogenetic tree, the protein of AaERF1 had close evolutionary relationships to AtERF2, LeERF1, NtERF1 and TaERF3 which showed that they might share similar functions in disease resistance (Figure S2B).Results AaERF1 is Ubiquitously Expressed in A. annuaThe promoter sequence of AaERF1(JQ513909)was cloned by genomic walking (Figure 1A). To observe the expression pattern of AaERF1 in details, the AaERF1 promoter was subcloned to the pCAMBIA1391Z vector (Figure 1B) and then AaERF1 promoterGUS transgenic A. annua plants were generated. Six lines of the transgenic A. annua plants expressing the GUS and three lines for the wild-type background were prepared. All the lines showed similar fusion protein expression. GUS activity was detected in all tissues examined, including roots, stems, leaves and flowers (Figure 2A, 2B, 2C and 2D). In 1-month-old plants, GUS activity was high in root tips, stems and leaves (Figure 2A, 2B and 2C). During the flowering period, GUS activity was also detected in flower buds. So, AaERF1 is ubiquitously expressed in A. annua. From Figure 2B and 2C, GUS expression was 10457188 also detected in the glandular trichomes and T-shaped trichomes. No signals were observed in the negative control plants transformed with pCAMBIA1391 empty vector (Figure S1).AaERF1 Protein Interacts with the GCC Box in vitroSince the AP2 domain of AaERF1 contained the key amino acids to bind the GCC box, the recombinant MBP-AaERF1 protein was constructed and overexpressed in E. coli BL21, purified, and used to examine the DNA binding ability in vitro. The purified MBP-AaERF1 protein was mixed, respectively, with the labeled wild-type GCC probe or a mutated GCC probe in the binding reaction. The results of EMSA showed that the gel mobility shift was specific to the MBP-AaERF1 protein with the labeled GCC probe (lane 2 in Figure 4A). As expected, there were no shifted bands in the combination of MBP-AaERF1 plus the mutated GCC (mGCC) probe (lane 5 in Figure 4A) and in the negative controls, including MBP with the labeled GCC probe (lane 1) or mGCC probe (lane 4), and only the labeled GCC probe (lane 3) or mGCC probe (lane 6) (Figure 4A). The results demonstrated that AaERF1 was able to bind to the GCC box cisacting element, but not to the mut.