A sorghum (Sorghum bicolor) mutant with altered carbon isotope ratio. uri icon

abstract

  • Recent efforts to engineer C-4 photosynthetic traits into C-3 plants such as rice demand an understanding of the genetic elements that enable C-4 plants to outperform C-3 plants. As a part of the C-4 Rice Consortium's efforts to identify genes needed to support C-4 photosynthesis, EMS mutagenized sorghum populations were generated and screened to identify genes that cause a loss of C-4 function. Stable carbon isotope ratio (delta C-13) of leaf dry matter has been used to distinguishspecies with C-3 and C-4 photosynthetic pathways. Here, we report the identification of a sorghum (Sorghum bicolor) mutant with a low delta C-13 characteristic. A mutant (named Mut33) with a pale phenotype and stunted growth was identified from an EMS treated sorghum M-2 population. The stable carbon isotope analysis of the mutants showed a decrease of C-13 uptake capacity. The noise of random mutation was reduced by crossing the mutant and its wildtype (WT). The back-cross (BC1F1) progenies were like the WT parent in terms of C-13 values and plant phenotypes. All the BC1F2 plants with low delta C-13 died before they produced their 6 th leaf. Gas exchange measurements of the low delta C-13 sorghum mutants showed a higher CO2 compensation point (25.24 mu mol CO2. mol(-1) air) and the maximum rate of photosynthesis was less than 5 mu mol.m(-2). s(-1). To identify the genetic determinant of this trait, four DNA pools were isolated; two each from normal and low delta C-13 BC1F2 mutant plants. These were sequenced using an Illumina platform. Comparison of allele frequency of the single nucleotide polymorphisms (SNPs) between the pools with contrasting phenotype showed that a locus in Chromosome 10 between 57,941,104 and 59,985,708 bps had an allele frequency of 1. There were 211 mutations and 37 genes in the locus, out of which mutations in 9 genes showed non-synonymous changes. This finding is expected to contribute to future research on the identification of the causal factor differentiating C-4 from C-3 species that can be used in the transformation of C-3 to C-4 plants.

publication date

  • 2017
  • 2017
  • 2017