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Purification of Protein AP-Toxin from Arthrinium phaeospermum Causing Blight in Bambusa pervariabilis × Dendrocalamopisis grandis and Its Metabolic Effects on Four Bamboo Varieties

First, second, fourth, fifth, and seventh authors: College of Forestry, Sichuan Agricultural University, Ya'an 625014, China; second and sixth authors: Key Laboratory of Forest Protection of Sichuan Province, Sichuan Agricultural University, Ya'an 625014, China; and third author: Department of Foreign Affairs Administration, Chengdu Institute, Sichuan International Studies University, Chengdu 611731, China.

Bambusa pervariabilis × Dendrocalamopisis grandis blight is caused by a toxin produced by the fungus Arthrinium phaeospermum. In this study, a toxin fraction (P1-2-2) with an estimated molecular mass of 31 kDa was purified from a culture filtrate of this fungus by ammonium sulfate precipitation, Sephadex G-50 gel chromatography, Q Sepharose Fast Flow anion exchange resin, and Sephadex G-75 chromatography. The N-terminal amino acid sequence (i.e., H₂N-Gln-Val-Arg-Asp-Arg-Leu-Glu-Ser-Thr) determined by Edman degradation showed homology to known serine alkaline proteases. The purified protein was named AP-toxin. Effects of the purified protein toxin on total phenol, flavonoid, total nucleic acid, DNA, RNA, soluble protein, and soluble sugar content, as well as DNase and RNase activities and disease index, were analyzed in different bamboo varieties by the impregnation method. The toxin had a significant effect on each parameter tested. In addition, a significant correlation was observed among the metabolic index, treatment time, bamboo resistance, and disease index. These data suggest that AP-toxin plays an important role in mediating the phytotoxic activities of A. phaeospermum. This study also indicates that metabolic indices could reflect the resistance indices of hybrid bamboo to blight.

Additional keywords: disease resistance, phytotoxic activity.