Cloning and characterization of sorghum bicolor redroot mutant candidate genes



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Sorghum (Sorghum bicolor) is known for its adaptability to adverse environmental conditions such as drought and high temperature and currently used as a bioenergy feedstock. The sorghum plant is known to produce distinct natural products. Phytoalexins are synthesized by sorghum plants as an active defense mechanism against the pathogen infection. Screening of mutant library developed from EMS mutagenized sorghum BTx623 seeds resulted in identification of mutant (redroot). Whole genome resequencing and analysis with MutMAP pipeline resulted in identification of 24 candidate genes. Confirmation with sanger sequencing could not identify the causal mutation possibly due to smaller number of individual homozygous F2 mutants (13 plants) used for MutMAP was less and did not comprise enough recombination in the population. Additional crosses were made to advance to BC2F3 population to fine map the region. Since, the initial 24 candidate gene list had 2 interesting genes related to monolignol glucosidase and the mutations were segregating with the phenotype, we have evaluated the function of the two sorghum genes using Arabidopsis model system. The main hypothesis was by introducing the sorghum wild type and mutant allele for BGLU45 and BGLU46, the Arabidopsis Col-0 and mutant’s roots produce red colored phenolic compounds only in case of mutant allele but not in case of wild type allele. However, the transgenic Arabidopsis expressing the candidate genes and the mutants did not show the expected redroot phenotype in any case, which we think could be due to species level differences (monocot/dicot) or due to less protein sequence similarity. Interestingly the BGLU mutants produced high biomass which reflected the role of secondary metabolite biosynthesis in overall growth and development of plants. We are pursuing the functional characterization of these mutants for their role in increased biomass.

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Sorghum, Redroot, Cloning, Candidate gene