Journal Article

Induction of a Novel XIP-Type Xylanase Inhibitor by External Ascorbic Acid Treatment and Differential Expression of XIP-Family Genes in Rice

Takaaki Tokunaga and Muneharu Esaka

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 48, issue 5, pages 700-714
Published in print May 2007 | ISSN: 0032-0781
Published online May 2007 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcm038
Induction of a Novel XIP-Type Xylanase Inhibitor by External Ascorbic Acid Treatment and Differential Expression of XIP-Family Genes in Rice

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

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Rice microarray analysis showed that a number of stress-related genes are induced by external addition of l-ascorbic acid (AsA). The gene designated as AK073843 which is homologous to class Ш chitinase was found to exhibit the highest induction among these genes. However, its crucial residues within the chitinase active site are substituted with other residues, suggesting that the protein has no chitinase activity. The recombinant protein which is encoded by the AK073843 gene produced in Escherichia coli has xylanase inhibitor activity, indicating that the gene encodes a novel rice XIP-type xylanase inhibitor protein (OsXIP). The expression of OsXIP was enhanced not only by exogenous AsA treatment but also by various stresses such as citrate and sodium chloride treatments, and wounding; however, it was not influenced by increasing endogenous AsA content. External AsA treatment caused a significant increase in electrolyte leakage from rice root. These results suggested that OsXIP was induced by stress which is caused by external AsA treatment. Rice XIP-family genes, OsXIP, riceXIP and RIXI, showed differential organ-specific expression. Also, these genes were differentially induced by stress and stress-related phytohormones. The transcripts of OsXIP and riceXIP were undetectable under normal conditions, and were drastically induced by wounding and methyl jasmonate (MeJA) treatment in the root. RIXI was constitutively expressed in the shoot but not induced by wounding and stress-related phytohormones. Thus, XIP-type xylanase inhibitors were suggested to be specialized in their function and involved in defense mechanisms in rice.

Keywords: Ascorbic acid; DNA microarray; Oryza sativa; Stress response; Xylanase inhibitor

Journal Article.  7762 words.  Illustrated.

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

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