Identical substitutions in magnesium chelatase paralogs result in chlorophyll-deficient soybean mutants.
Bottom Line: This mutation was identified in the ChlI1b gene, a paralog of ChlI1a.Protein sequence alignments of the two Mg-chelatase subunits indicated that the sites of amino acid modification in MinnGold, T219H, and CD-5 are highly conserved among photosynthetic species.These results suggest that amino acid alterations in this critical domain may create competitive inhibitory interactions between the mutant and wild-type ChlI1a and ChlI1b proteins.
Affiliation: Department of Agronomy and Plant Genetics, University of Minnesota, St. Paul, Minnesota 55108.Show MeSH
Mentions: Palmer et al. (1989) found that the y11 and CD-5 chlorophyll deficient mutants display nearly identical chlorophyll deficient phenotypes (Figure S1). Allelism test results and similarity in phenotype led the authors (Palmer et al. 1989) to initially consider that the two mutants were allelic and thus were surprised to find that CD-5 cosegregated with the blunt pubescence tip locus (pb) on chromosome 15. After identifying the likely y11 causative mutation in a Mg-chelatase subunit, we identified a Mg-chelatase paralog on chromosome 15, Glyma15g08680, as a candidate gene for the CD-5. Sequencing of Glyma15g08680 from two homozygous CD-5 individuals and from two wild-type individuals all derived from a segregating family identified a single non-synonymous SNP in the third exon. A CAPS assay of seventeen individuals segregating for the presence of CD-5 showed prefect cosegregation of the candidate SNP with the mutant phenotype (Figure S3). These results suggest that the identified SNP is causative of the CD-5 chlorophyll-deficient phenotype. A comparative sequence analysis across 29 diverse soybean lines (McHale et al. 2012) found that the single base substitution in Glyma15g08680 was unique to CD-5. All 29 of the diverse lines exhibited the wild-type sequence (Figure S4A). Remarkably, the Glyma15g08680 amino acid change in CD-5 (Q275R) was identical in position and sequence to the Glyma13g30560 change in y11 (Q275R) (Figure 5 and Figure S4B).
Affiliation: Department of Agronomy and Plant Genetics, University of Minnesota, St. Paul, Minnesota 55108.