*2.4. Identification of Nuclear-Encoded Mitochondrial Intron Maturases in the Soybean Genome*

By using the protein sequences of the four Arabidopsis nuclear maturases as baits to search the soybean genome, six homologous nuclear maturases were identified. Among these transcripts, two are likely to have arisen from gene duplication (Figure 2). The expression levels of these six transcripts are presented in Supplementary Table S4. Among these six transcripts, only a transcript homologous to *AtnMAT4* had a significantly higher (2X) expression in N than in UR. By contrast, four transcripts homologous to *AtnMAT1-4* expressed significantly higher in SR than in UR (Supplementary Table S4).
