Identification of atairp2 loss-of-function mutants, sequence analysis of the AtAIRP2 gene, and construction of AtAIRP2 overexpressors. A, Schematic representation of the atairp2-1 (SAIL_686_G08) and atairp2-2 (Salk_005082) alleles with T-DNA insertions. Gray bars indicate coding regions, black bars indicate the 5′ and 3′ untranslated regions, and solid lines represent introns of the AtAIRP2 gene (GenBank accession no. NM_120230). T-DNA insertions are indicated by triangles. T-DNA-specific (LB1 and LB2) and gene-specific (FW1, FW2, FW3, RV1, RV2, and RV3) primers used in genotyping PCR and RT-PCR are indicated with arrows. B, Genotyping PCR of the two atairp2 T-DNA insertion mutant alleles (atairp2-1 and atairp2). Gene-specific and T-DNA-specific primer sets used for genomic PCRs are indicated on the right. WT, Wild type. C, Expression levels of AtAIRP2 transcripts in wild-type and atairp2 mutant plants. Gene-specific primer sets for RT-PCR are indicated on the right. Constitutively expressed UBC10 (for E2 ubiquitin-conjugating enzyme) mRNA was used as a loading control. Primer sequences are listed in Supplemental Table S1. D, Schematic structure of the full-length AtAIRP2 cDNA clone and its deduced protein. The gray bar indicates the coding region, and solid lines represent the 5′ and 3′ untranslated regions. The C-terminal C3HC4-type RING domain is indicated by the black bar. E, Phylogenetic analysis of the seven AtAIRP2 homologs from Arabidopsis (At5g58787 and At3g47160), rice (GenBank accession no. NP_001060539), poplar (XP_002309135), grape (XP_002280008), and sorghum (XP_002447334). F, Amino acid sequence alignment of the RING motifs of AtAIRP2 and other C3HC4-type RING proteins. Potential Zn2+-interacting amino acid residues (C-X2-C-X11-C-X1-H-X2-C-X2-C-X10-C-X2-C) are indicated. Amino acid residues identical in all seven RING domains are shown in black, and those conserved in at least four of the seven sequences are shaded. G, Real-time qRT-PCR analysis of the wild type and AtAIRP2 overexpressors. Expression levels of AtAIRP2 transcripts in wild-type and T3 35S:AtAIRP2-sGFP transgenic (independent lines 10 and 19) plants were determined by real-time qRT-PCR using gene-specific primer sets. UBC10 mRNA levels were used as a loading control. H, Immunoblot analysis of wild-type and AtAIRP2-sGFP (lines 10 and 19) plants. Expression levels of the AtAIRP2-sGFP fusion protein were determined using an anti-GFP antibody. Rubisco large subunit (RbcL) was used as a loading control.