Genome-wide screening and expression analysis of genes encoding E2 ubiquitin-conjugating enzymes in tomato. (a) Phylogenetic analysis of tomato E2s. Phylogenetic tree was produced using MEGA version 5.2. Bootstrap values from 1,000 replications for each branch are shown. (b) Gene expression analysis of tomato E2s in wild-type (WT) and rin mutant during the period of fruit ripening, as determined by quantitative RT-PCR. The actin gene was used as the internal control. The stages of fruit ripening include mature green (MG), breaker (Br), orange (Or) and red ripe (RR). Values are means ± SD of three independent experiments. Asterisks indicate values that changed more than twofold in the rin mutant at indicated ripening stages.