Characterization of a newly identified rice chitinase-like protein (OsCLP) homologous to xylanase inhibitor.

Jingni Wu,Sang Gon Kim,Kyu Young Kang,Yiming Wang,Sun Tae Kim

doi:10.1186/1472-6750-13-4

Jingni Wu, Sang Gon Kim + Show 3 more

Open Access

https://doi.org/10.1186/1472-6750-13-4

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Abstract

BackgroundDuring rice blast fungal attack, plant xylanase inhibitor proteins (XIPs) that inhibit fungal xylanase activity are believed to act as a defensive barrier against fungal pathogens. To understand the role of XIPs in rice, a xylanase inhibitor was cloned from rice. The expression of this gene was examined at the transcriptional/translational levels during compatible and incompatible interactions, and the biochemical activity of this protein was also examined.ResultsSequence alignment revealed that the deduced amino acid sequence of OsCLP shares a high degree of similarity with that of other plant TAXI-type XIPs. However, recombinant OsCLP did not display inhibitory activity against endo-1,4-β-xylanase enzymes from Aureobasidium pullulans (A. pullulans) or Trichoderma viride (T. viride). Instead, an in-gel activity assay revealed strong chitinase activity. The transcription and translation of OsCLP were highly induced when rice was exposed to pathogens in an incompatible interaction. In addition, exogenous treatment with OsCLP affected the growth of the basidiomycete fungus Rhizoctonia solani through degradation of the hyphal cell wall. These data suggest that OsCLP, which has chitinase activity, may play an important role in plant defenses against pathogens.ConclusionsTaken together, our results demonstrate that OsCLP may have antifungal activity. This protein may directly inhibit pathogen growth by degrading fungal cell wall components through chitinase activity.

Highlights

During rice blast fungal attack, plant xylanase inhibitor proteins (XIPs) that inhibit fungal xylanase activity are believed to act as a defensive barrier against fungal pathogens
Sequence analysis and characterization of OsCLP From previous apoplastic secretome analysis of the rice blast fungus interaction, an XIP, which was highly expressed upon Magnaporthe oryzae (M. oryzae) infection, was isolated and identified
Previous studies have suggested that XIPs are associated with defense, as they play a significant role in protecting host plants from pathogen attack [11]

Summary

Introduction

During rice blast fungal attack, plant xylanase inhibitor proteins (XIPs) that inhibit fungal xylanase activity are believed to act as a defensive barrier against fungal pathogens. To understand the role of XIPs in rice, a xylanase inhibitor was cloned from rice. The expression of this gene was examined at the transcriptional/ translational levels during compatible and incompatible interactions, and the biochemical activity of this protein was examined. Plants secrete a group of proteinaceous xylanase inhibitors to suppress pathogenic xylanases. These proteins are thought as “defense molecules”. That protect plant cells from attack by pathogenic hydrolytic enzymes [11]. Biochemical analysis revealed that a wheat XIP inhibits the expression of family-10 and −11 xylanases from Aspergillus nidulans and Aspergillus niger, respectively [15], while a TAXI inhibits the expression of the family-11 xylanase (but not the family-10 xylanase) of A. niger and Bacillus subtilis [13,16]

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