Phenotypes of atprmt3 null mutants. (A) The gene structure of AtPRMT3 and locations of the T-DNA insertions in atprmt3 mutants. (B) RT-PCR analysis of the full-length AtPRMT3 transcript in wild-type Col and two atprmt3 mutants (Upper). Actin2 was used as an internal control (Lower). (C) Western blot analysis of AtPRMT3 protein in wild-type Col, atprmt3 mutants, and the complemented line AtPRMT3-GUS (Upper). Rubisco large subunit stained with Ponceau S was used as an internal control (Lower). (D) atprmt3 mutants exhibit an aberrant vein pattern in cotyledons and a typical pointed phenotype in the first true leaf. The numerator and denominator described in the figure represent the numbers of aberrant leaves and total leaves detected, respectively. [Scale bars, 10 mm for seedlings (Upper), 1 mm for cotyledons (Middle), 2 mm for the first true leaf (Lower).] (E) The polyribosome profile, monitored by absorbance at 254 nm over 5–50% sucrose gradient, in atprmt3-2 shows down-regulation of the 60S large subunit and 80S monosome but up-regulation of polyribosomes.