Induction of a novel XIP-type xylanase inhibitor by external ascorbic acid treatment and differential expression of XIP-family genes in rice
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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DOI：
10.1093/pcp/pcm038
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发表时间：
2007-05-01
影响因子：
4.9
通讯作者：
Esaka, Muneharu
中科院分区：
文献类型：
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作者：
Tokunaga, Takaaki;Esaka, Muneharu
水稻基因芯片分析表明，外源添加L-抗坏血酸（阿萨）诱导了许多与胁迫相关的基因。命名为AK 073843的基因与III类几丁质酶同源，发现在这些基因中表现出最高的诱导。然而，其几丁质酶活性位点内的关键残基被其他残基取代，表明该蛋白没有几丁质酶活性。在大肠杆菌中产生的AK 073843基因编码的重组蛋白具有木聚糖酶抑制剂活性，表明该基因编码一种新的水稻XIP型木聚糖酶抑制剂蛋白（OsXIP）。OsXIP的表达不仅受外源阿萨处理的影响，也受柠檬酸盐、氯化钠处理和创伤等胁迫的影响，但不受内源阿萨含量的影响。外源阿萨处理引起水稻根系电解质渗漏显著增加。这些结果表明OsXIP是由外部阿萨处理引起的应激诱导的。水稻XIP家族基因OsXIP、水稻XIP和RIXI在水稻中的表达存在器官特异性。此外，这些基因的差异诱导的压力和压力相关的植物激素。OsXIP和riceXIP的转录本在正常条件下检测不到，并且在根中受到伤害和茉莉酸甲酯（MeJA）处理的强烈诱导。RIXI在芽中组成型表达，但不受创伤和应激相关的植物激素诱导。因此，XIP类木聚糖酶抑制剂的功能是专门的，并参与水稻的防御机制。
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 III 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, rice XIP 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.