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To gain a better understanding of the molec-ular mechanisms of photosystem I (PSI) biogenesis, we characterized the Arabidopsis thaliana photosystem I bio-genesis factor 2 (pbf2) mutant, which lacks PSI complex. PBF2 encodes a P-class pentatricopeptide repeat (PPR) protein. In the pbf2 mutants, we observed a striking de-crease in the transcript level of only one gene, the chloroplast gene ycf3, which is essential for PSI assembly. Further analysis of ycf3 transcripts showed that PBF2 is specifically required for the splicing of ycf3 intron 1. Computational prediction of binding sequences and elec-trophoretic mobility shift assays reveal that PBF2 specifi-cally binds to a sequence in ycf3 intron 1. Moreover, wefound that PBF2 interacted with two general factors for group Ⅱ intron splicing CHLOROPLAST RNA SPLICING2-ASSOCIATED FACTOR1 (CAF1) and CAF2, and facilitated the association of these two factors with ycf3 intron 1. Our results suggest that PBF2 is specifically required for the splicing of ycf3 intron 1 through cooperating with CAF1 and CAF2. Our results also suggest that additional proteins are required to contribute to the specificity of CAF-dependent group Ⅱ intron splicing.