Bx1 benzoxazin1

Based on submission by Monika Frey to the MaizeGDB and the Maize Genetics Cooperation Newsletter.

Function Maize gene for first step in biosynthesis of benzoxazin, which aids in resistance to insect pests, pathogenic fungi and bacteria.

First report Hamilton 1964,[1] as a mutant sensitive to the herbicide atrazine, and lacking benzoxazinoids (less than 1% of non-mutant plants).

Mutations in the bx1 gene reduce the resistance to first generation European corn borer that is conferred by benzoxazinoids. Molecular characterization reveals that the BX1 protein is a homologue to the alpha-subunit of tryptophan synthase. The reference mutant allele has a deletion of about 900 bp, located at the 5'-terminus and comprising sequence upstream of the transcription start site and the first exon. A second mutant allele is given by a Mu transposon insertion in the fourth exon (Frey et al. 1997[2] ). Gene sequence diversity analysis has been performed for 281 inbred lines of maize, and the results suggest that bx1 is responsible for much of the natural variation in DIMBOA (a benzoxazinoid compound) synthesis (Butron et al. 2010).[3]

Map location

AB chromosome translocation analyses place on short arm of chromosome 4 (4S; Simcox and Weber 1985[4] ). There is close linkage to other genes in the benzoxazinoid synthesis pathway [bx2, bx3, bx4, bx5 Frey et al. 1995,[5] 1997[2] ). Gene bx1 is 2490 bp from bx2 (Frey et al. 1997[2] ); between umc123 and agrc94 on 4S (Melanson et al. 1997[6] ). Mapping probes: SSR p-umc1022 (Sharopova et al. 2002[7] ); Overgo (physical map probe) PCO06449 (Gardiner et al. 2004[8] ).

Phenotypes

Mutants are viable, but may be distinguished from normal plants by FeCl3 staining: plants able to synthesize benzoxinoids have pale blue color when crushed and treated with FeCl3 solutions (Hamilton 1964,[1] Simcox 1993[9] )

Gene Product

Catalyzes the first step in the synthesis of DIMBOA, forming indole from indole-3-glycerol phosphate. The enzyme is called indole-3-glycerol phosphate lyase, chloroplast, EC 4.1.2.8 and is located in the chloroplast. The X-ray structure of BX1 protein has been resolved and compared with bacterial TSA (tryptophan synthase alpha subunit, Kulik et al. 2005).[10] Three homologs of the BX1 protein occur in maize. One is encoded by the gene tsa1, tryptophan synthase alpha1(Frey et al. 1997,[2] Melanson et al. 1997[6] ), on chromosome 7, another by igl1, indole-3-glycerol phosphate1(Frey et al. 1997,[2] on chromosome 1, and another by tsah1, 'TSA like" and located near the bx1 gene (Frey et al. 1997.[2] ).

Links

References

  1. 1 2 Hamilton, RH (1964). "A corn mutant deficient in 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one with an altered tolerance of atrazine". Weeds. 12: 27–30. JSTOR 4040633.
  2. 1 2 3 4 5 6 Frey, M; Chomet, P; Glawischnig, E; Stettner, C; Grün, S; Winklmair, A; Eisenreich, W; Bacher, A; Meeley, RB; Briggs, SP; Simcox, K; Gierl, A (Aug 1, 1997). "Analysis of a chemical plant defense mechanism in grasses.". Science. 277 (5326): 696–9. doi:10.1126/science.277.5326.696. PMID 9235894.
  3. ↑ Butrón, A; Chen, YC; Rottinghaus, GE; McMullen, MD (Feb 2010). "Genetic variation at bx1 controls DIMBOA content in maize.". TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik. 120 (4): 721–34. doi:10.1007/s00122-009-1192-1. PMID 19911162.
  4. ↑ Simcox, K. D.; Weber, D. F. (1985). "Location of the Benzoxazinless (bx) Locus in Maize by Monosomic and B-A Translocational Analyses1". Crop Science. 25 (5): 827. doi:10.2135/cropsci1985.0011183X002500050024x.
  5. ↑ Frey, M; Kliem, R; Saedler, H; Gierl, A (Jan 6, 1995). "Expression of a cytochrome P450 gene family in maize.". Molecular & general genetics : MGG. 246 (1): 100–9. doi:10.1007/bf00290138. PMID 7823905.
  6. 1 2 Melanson, D; Chilton, MD; Masters-Moore, D; Chilton, WS (Nov 25, 1997). "A deletion in an indole synthase gene is responsible for the DIMBOA-deficient phenotype of bxbx maize.". Proceedings of the National Academy of Sciences of the United States of America. 94 (24): 13345–50. doi:10.1073/pnas.94.24.13345. PMC 24311Freely accessible. PMID 9371848.
  7. ↑ Sharopova, N; McMullen, MD; Schultz, L; Schroeder, S; Sanchez-Villeda, H; Gardiner, J; Bergstrom, D; Houchins, K; Melia-Hancock, S; Musket, T; Duru, N; Polacco, M; Edwards, K; Ruff, T; Register, JC; Brouwer, C; Thompson, R; Velasco, R; Chin, E; Lee, M; Woodman-Clikeman, W; Long, MJ; Liscum, E; Cone, K; Davis, G; Coe EH, Jr (Mar–Apr 2002). "Development and mapping of SSR markers for maize.". Plant molecular biology. 48 (5-6): 463–81. PMID 12004892.
  8. ↑ Gardiner, J; Schroeder, S; Polacco, ML; Sanchez-Villeda, H; Fang, Z; Morgante, M; Landewe, T; Fengler, K; Useche, F; Hanafey, M; Tingey, S; Chou, H; Wing, R; Soderlund, C; Coe EH, Jr (Apr 2004). "Anchoring 9,371 maize expressed sequence tagged unigenes to the bacterial artificial chromosome contig map by two-dimensional overgo hybridization.". Plant Physiology. 134 (4): 1317–26. doi:10.1104/pp.103.034538. PMID 15020742.
  9. ↑ Simcox, KD (1993). "Screening large populations for recessive bx1 genotypes; a variation of the FeCl3 root-tip squash assay". Maize Genetics Cooperation Newsletter. 67: 116. Retrieved Dec 24, 2013.
  10. ↑ Kulik, V; Hartmann, E; Weyand, M; Frey, M; Gierl, A; Niks, D; Dunn, MF; Schlichting, I (Sep 23, 2005). "On the structural basis of the catalytic mechanism and the regulation of the alpha subunit of tryptophan synthase (TSA) from Salmonella typhimurium and BX1 from maize, two evolutionarily related enzymes.". Journal of Molecular Biology. 352 (3): 608–20. doi:10.1016/j.jmb.2005.07.014. PMID 16120446.
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