Journal Article

New TAXI-type Xylanase Inhibitor Genes are Inducible by Pathogens and Wounding in Hexaploid Wheat

Tomoko Igawa, Tetsuko Ochiai-Fukuda, Naoko Takahashi-Ando, Shuichi Ohsato, Takehiko Shibata, Isamu Yamaguchi and Makoto Kimura

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 45, issue 10, pages 1347-1360
Published in print October 2004 | ISSN: 0032-0781
Published online October 2004 | e-ISSN: 1471-9053 | DOI:
New TAXI-type Xylanase Inhibitor Genes are Inducible by Pathogens and Wounding in Hexaploid Wheat

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry


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TAXI-I (Triticum aestivum xylanase inhibitor I) is a wheat grain protein that inhibits arabinoxylan fragmentation by microbial endo-β-1,4-xylanases used in the food industry. Although TAXI was speculated to be involved in counterattack against pathogens, there is actually no evidence to support this hypothesis. We have now demonstrated the presence of TAXI family members with isolation of two mRNA species, Taxi-III and Taxi-IV. At the nucleotide sequence level, Taxi-III and Taxi-IV were 91.7% and 92.0% identical, respectively, to Taxi-I, and Taxi-III and Taxi-IV were 96.8% identical. Accumulation of Taxi-III/IV transcripts was most evident in roots and older leaves where transcripts of Taxi-I were negligible. When challenged by fungal pathogens Fusarium graminearum and Erysiphe graminis, the concentrations of Taxi-III/IV transcripts increased significantly. In contrast, the increases in Taxi-I transcripts in response to these pathogens were rather limited. Both Taxi-I and Taxi-III/IV were strongly expressed in wounded leaves. The upstream region of Taxi-III contained W boxes and GCC boxes, which are sufficient to confer pathogen and wound inducibility on promoters. Recombinant TAXI-III protein inhibited Aspergillus niger and Trichoderma sp. xylanases: it was also active against some spelt xylan-induced xylanases of F. graminearum. These features suggest that some, but not all, TAXI-type xylanase inhibitors have a role in plant defense.

Keywords: Keywords: Adaptive evolution — Cell-wall-degrading enzyme — Cereal crops — Differential expression — Fusarium head blight (FHB) — Virulence factor.; Abbreviations: as-1, activation sequence-1; CAPS, cleaved amplified polymorphic sequence; DIG, digoxigenin; EST, expressed sequence tag; ERF, ethylene-responsive factor; FHB, Fusarium head blight; IPTG, isopropyl-1-thio-β-d-galactopyranoside; PG, polygalacturonase; PGIP, PG-inhibiting protein; PR, pathogenesis-related; RACE, rapid amplification of cDNA ends; RT-PCR, reverse transcription-PCR; SA, salicylic acid; SP, signal peptide; TAIL-PCR, thermal asymmetric interlaced-PCR; TF, transcription factor.

Journal Article.  9617 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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