Verification of AtMEK1 mutants and RT-PCR analyses for AtMEK1 over-expressing plants. (A) LB, T-DNA left border; RB, T-DNA right border. Black boxes represent exons. The T-DNA insert is not drawn to scale. The black arrows at LB indicate the T-DNA left border primer, and the black arrows indicate the AtMEK1-specific primers used for mutant isolation. (B) Verification of AtMEK1 mutant, mek1. Reverse transcription-polymerase chain reaction (RT-PCR) analysis for AtMEK1 transcript. The AtMEK1 transcript was present in total RNA from wild-type Arabidopsis but absent in the AtMEK1 mutant. As a control, Actin2 primers that amplify a 500 bp product were added together with AtMEK1 primers in each PCR reaction. (C) The transcript levels of AtMEK1 in different over-expression lines analysed by RT-PCR. Total RNA was extracted from wild-type plants or AtMEK1 over-expressing plants.