Bx1 benzoxazin1

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).

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. Additional alleles are given by a Mu transposon insertion in the fourth exon (Frey et al. 1997[2] ) and a Ds transposon insertion in the maize inbred line W22 genetic background (Betsiashvili et al. 2014[3]). 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).[4] Genetic variation in benzoxazinoid content influences maize resistance to several insect pests (Meihls et al. 2013;[5] McMullen et al. 2009[6]).

Map location

AB chromosome translocation analyses place on short arm of chromosome 4 (4S; Simcox and Weber 1985[7] ). There is close linkage to other genes in the benzoxazinoid synthesis pathway [bx2, bx3, bx4, bx5 Frey et al. 1995,[8] 1997[2] ). Gene bx1 is 2490 bp from bx2 (Frey et al. 1997[2] ); between umc123 and agrc94 on 4S (Melanson et al. 1997[9] ). Mapping probes: SSR p-umc1022 (Sharopova et al. 2002[10] ); Overgo (physical map probe) PCO06449 (Gardiner et al. 2004[11] ).

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[12] ). Mutations in the bx1 gene reduce the resistance to first generation European corn borer (Ostrinia nubilalis) that is conferred by benzoxazinoids (Klun et al. 1970 [13]). Bx1 mutant maize deposited less callose in response to chitosan elicitation than isogenic wildtype plants (Ahmad et al. 2011 [14]). Genetic mapping using recombinant inbred lines derived from maize inbred lines B73 and Mo17 showed that a 3.9 kb cis-regulatory element that is located approximately 140 kb upstream of Bx1 causes higher 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) accumulation in Mo17 than in B73 seedlings (Zheng et al. 2015 [15]). This genetic variation is also associated with higher corn leaf aphid (Rhopalosiphum maidis) reproduction on B73 compared to Mo17 maize seedlings (Betsiashvili et al. 2014 [3]). Relative to maize inbred line W22, Bx1::Ds mutant maize plants are more sensitive to corn leaf aphids (Rhopalosiphum maidis) (Betsiashvili et al. 2014[3]) and beet armyworms (Spodoptera exigua) (Tzin et al. 2017 [16]). Highly localized induction of benzoxazinoid accumulation in response to Egyptian cotton leafworm (Spodoptera littoralis) feeding is abolished in a maize bx1 mutant (Maag et al. 2016 [17]).

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).[18] 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[9] ), on chromosome 7, another by igl1, indole-3-glycerol phosphate lyase1(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] ).

References

  1. ^ a b 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 (1): 27–30. doi:10.2307/4040633. JSTOR 4040633.
  2. ^ a b c d e f 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. ^ a b c Betsiashvili, M.; Ahern, K. R.; Jander, G. (2015). "Additive effects of two quantitative trait loci that confer Rhopalosiphum maidis (corn leaf aphid) resistance in maize inbred line Mo17". Journal of Experimental Botany. 66 (2): 571–578. doi:10.1093/jxb/eru379. ISSN 0022-0957. PMC 4286405. PMID 25249072.
  4. ^ Butrón, A; Chen, YC; Rottinghaus, GE; McMullen, MD (Feb 2010). "Genetic variation at bx1 controls DIMBOA content in maize" (PDF). Theoretical and Applied Genetics. 120 (4): 721–34. doi:10.1007/s00122-009-1192-1. hdl:10261/24875. PMID 19911162. S2CID 33310126.
  5. ^ Meihls, L. N.; Kaur, H.; Jander, G. (2012). "Natural Variation in Maize Defense against Insect Herbivores". Cold Spring Harbor Symposia on Quantitative Biology. 77: 269–283. doi:10.1101/sqb.2012.77.014662. ISSN 0091-7451. PMID 23223408.
  6. ^ McMullen, Michael D.; Frey, Monika; Degenhardt, Jörg (2009), Bennetzen, Jeff L.; Hake, Sarah C. (eds.), "Genetics and Biochemistry of Insect Resistance in Maize", Handbook of Maize: Its Biology, Springer New York, pp. 271–289, doi:10.1007/978-0-387-79418-1_14, ISBN 9780387794174
  7. ^ 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.
  8. ^ Frey, M; Kliem, R; Saedler, H; Gierl, A (Jan 6, 1995). "Expression of a cytochrome P450 gene family in maize". Molecular & General Genetics. 246 (1): 100–9. doi:10.1007/bf00290138. PMID 7823905. S2CID 29908288.
  9. ^ a b 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. Bibcode:1997PNAS...9413345M. doi:10.1073/pnas.94.24.13345. PMC 24311. PMID 9371848.
  10. ^ 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. doi:10.1023/a:1014868625533. PMID 12004892. S2CID 25157785.
  11. ^ 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. PMC 419808. PMID 15020742.
  12. ^ 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.
  13. ^ Klun, Jerome A.; Guthrie, W. D.; Hallauer, Arnel R.; Russell, W. A. (1970). "Genetic Nature of the Concentration of 2,4-dihydroxy-7-methoxy 2H-l,4-benzoxazin- 3(4H)-one and Resistance to the European Corn Borer in a Diallel Set of Eleven Maize Inbreds1". Crop Science. 10 (1): 87. doi:10.2135/cropsci1970.0011183X001000010032x. ISSN 0011-183X.
  14. ^ Ahmad, Shakoor; Veyrat, Nathalie; Gordon-Weeks, Ruth; Zhang, Yuhua; Martin, Janet; Smart, Lesley; Glauser, Gaétan; Erb, Matthias; Flors, Victor (2011). "Benzoxazinoid Metabolites Regulate Innate Immunity against Aphids and Fungi in Maize". Plant Physiology. 157 (1): 317–327. doi:10.1104/pp.111.180224. ISSN 0032-0889. PMC 3165881. PMID 21730199.
  15. ^ Zheng, Linlin; McMullen, Michael D.; Bauer, Eva; Schön, Chris-Carolin; Gierl, Alfons; Frey, Monika (2015). "Prolonged expression of the BX1 signature enzyme is associated with a recombination hotspot in the benzoxazinoid gene cluster in Zea mays". Journal of Experimental Botany. 66 (13): 3917–3930. doi:10.1093/jxb/erv192. ISSN 1460-2431. PMC 4473990. PMID 25969552.
  16. ^ Tzin, Vered; Hojo, Yuko; Strickler, Susan R; Bartsch, Lee J; Archer, Cairo M; Ahern, Kevin R; Zhou, Shaoqun; Christensen, Shawn A; Galis, Ivan (2017). "Rapid defense responses in maize leaves induced by Spodoptera exigua caterpillar feeding". Journal of Experimental Botany. 68 (16): 4709–4723. doi:10.1093/jxb/erx274. ISSN 0022-0957. PMC 5853842. PMID 28981781.
  17. ^ Maag, Daniel; Köhler, Angela; Robert, Christelle A.M.; Frey, Monika; Wolfender, Jean-Luc; Turlings, Ted C.J.; Glauser, Gaétan; Erb, Matthias (2016). "Highly localized and persistent induction of Bx1 -dependent herbivore resistance factors in maize". The Plant Journal. 88 (6): 976–991. doi:10.1111/tpj.13308. PMID 27538820.
  18. ^ 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.