Effectiveness of sodium azide alone compared to sodium azide in combination with methyl nitrosurea for rice mutagenesis

Authors: Tai, Thomas; CHUN, AREUM - National Institute Of Crop Science, Iksan, South Korea; HENRY, ISABELLE - University Of California; NGO, KATHIE - University Of California; BURKART-WACO, DIANA - University Of California

Submitted to: Plant Breeding and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/12/2016
Publication Date: 11/30/2016
Citation: Tai, T., Chun, A., Henry, I.M., Ngo, K., Burkart-Waco, D. 2016. Effectiveness of sodium azide alone compared to sodium azide in combination with methyl nitrosurea for rice mutagenesis. Plant Breeding and Biotechnology. 4:453-461.

Interpretive Summary: Rice mutants derived from mutagenesis with sodium azide and sodium azide in combination with methyl nitrosourea were analyzed for their mutation densities (i.e. number of mutations in their DNA), mutation types, and the local DNA sequence adjacent to the mutation sites. Results indicate that sodium azide was as effective alone as in combination with methyl nitrosourea in generating mutations in rice thus indicating that treatment with the single chemical agent is the more efficient method. It was also determined that the mutations produced by sodium azide (and sodium azide plus methyl nitrosourea) were of the type most commonly generated by other chemical mutagens, but that the location of the mutated nucleotides (i.e. the nucleotides directly adjacent to the mutated nucleotide) differed from that observed for the common chemical mutagen ethyl methanesulfonate (EMS). This suggests that rice populations consisting of sodium azide mutants and EMS mutants are likely to contain a broader spectrum of mutations and are thus more likely to be useful for downstream applications such as mutation breeding and functional genomics.

Technical Abstract: Rice seeds of the temperate japonica cultivar Kitaake were mutagenized with sodium azide alone and in combination with methyl nitrosourea. Using the reduced representation sequencing method Restriction Enzyme Sequence Comparative Analysis (RESCAN), the mutation densities, types and local sequence context were determined in the resulting M2 generation mutants. The results indicate that sodium azide is as effective alone as in combination with methyl nitrosourea in generating mutations in rice. In both cases, GC > AT transitions were the predominant mutation type and similar local sequence contexts were observed (5’-G-G-R-3’ for sodium azide, 5’-R-G-R-3’ for sodium azide plus methyl nitrosourea). Differences in local sequence context with those reported for another common chemical mutagen, ethyl methanesulfonate, suggests that rice mutant populations developed by combining mutants derived independently from sodium azide and ethyl methanesulfonate may exhibit a broader spectrum of mutations and mutant phenotypes.