Expression regulation of a xylanase inhibitor gene riceXIP in rice (Oryza sativa L.)

riceXIP, a XIP-Type xylanase inhibitor gene identified in rice, was cloned and expressed in Escherichia coli. Recombinant protein riceXIP was active against xylanase from Aspergillus niger, suggesting correct expression. By using transgenic techniques, we achieved the overexpression of the riceXIP gene and gene knock-down plants and elucidated that riceXIP may likely participate in plant defence against herbivores. The defence-related genes were significantly elevated in riceXIP-overexpressing transgenic plants treated with rice brown planthopper infestation. The full-length promoter (2009 bp, RP1) of riceXIP gene and 1534 (RP2), 1179 (RP3), 891 (RP4), 491 (RP5), 400 (RP6), 214 (RP7) and 112 bp (RP8) 5′ deletion constructs were fused with β-glucuronidase (GUS) gene and transgenic rice plants were used to clarify its function. The transgenic lines transformed with promoter fragments of riceXIP differentially responded to methyl jasmonate and wounding stress by quantitative GUS analysis. The 5′ deletion analysis also showed that two repressor elements exist between −1502 and −1147 bp and between −182 and −80 bp, respectively, whereas an enhancer element exists between −1147 and −859 bp. The study strengthens the possibility that riceXIP participates in the resistance against herbivory in rice and provides a helpful insight for understanding the cis-regulation of the riceXIP gene.