**1. Introduction**

Photosynthesis is a vital process in which plants convert light energy into chemical energy [1,2]. In higher plants, chlorophyll *a* and *b* are the two major pigments located in the thylakoid membrane of photosynthetic organisms [2]. These chlorophyll molecules play essential roles in harvesting light energy and transferring that energy to reaction centers of the photosystem [2,3]. In the past few decades, tremendous research has been conducted on chlorophyll-deficient mutants in model plants, but the molecular genetic mechanisms underlying these soybean chlorophyll-deficiency mutations are not well understood.

For soybean, 15 chlorophyll-deficient mutant genes were reported to be mapped to chromosomes [4]. Of these genes, six lethal yellow mutant genes, including *Y11*, *Y18*/*Y18\_1*, *Y18\_2*, *YL\_PR350*, *PsbP*, and *CD-5*, were mapped to chromosomes 13, 14, 17, 15, 3 and 15, respectively [5–9]. The other nine viable yellow mutant genes, including *Y9*, *Y10*, *Y12*, *Y13*, *Y17*, *Y20*, *Y23*, *Tic110*, and *Cd1*, were mapped to chromosomes 15, 3, 6, 13, 15, 12, 13, 2, and 10, respectively [8,10–16]. However, only the function of *Y11* and *Y9* genes in yellow foliage was validated by complementary analysis [6,9].

RNA editing is a post-transcriptional modification process that changes the sequence of RNA molecules so that the information in the mature RNA differs from that defined in the genome [17]. In land plants, RNA editing occurs in transcripts of chloroplasts and mitochondria. There are 20–60 chloroplasts and over 300 RNA mitochondrial editing sites in most flowering plants [17,18]. RNA editing is

performed by an editosome that is assembled via protein-protein/RNA interactions [19]. Several organelle RNA recognition motif-containing (ORRM) proteins are known to be essential RNA editing factors. ORRM1 controls 62% of chloroplast editing sites in *Arabidopsis* and 81% of editing sites in maize, with the *Zm-orrm1* mutant exhibiting a pale green phenotype [20]. ORRM6 is primarily required for editing *psbF*-C77 and *accD*-C794 sites in *Arabidopsis* chloroplasts [21]. In addition, ORRM2, ORRM3, ORRM4 and ORRM5 are mitochondrial RNA editing factors [22–24]. Moreover, pentatricopeptide repeat (PPR) proteins, multiple organellar RNA editing factor (MORF)/RNA editing factor interacting proteins (RIPs), organelle zinc finger 1 (OZ1), protoporphyrinogen oxidase 1 (PPO1), and genomes uncoupled 1 (GUN1) have been identified as components of the plant RNA editosome [19,25–30].

Here, we report the characterization of a soybean *yellow leaf* (*yl*) mutant with chlorophyll deficiency and impaired photosynthesis. Fine mapping and DNA sequencing showed that *YL* encodes a GmORRM1. We showed that multiple chloroplast RNA editing sites were changed in *yl* mutants. Our findings provide new insight into the function of YL in soybean photosynthesis.
