Proteins induced in sorghum by the host-specific toxin from Periconia circinata: Purification, localization, and role in pathogenesis
Abstract
The response of Sorghum bicolor (L.) Moench to the host-specific toxin (PC-toxin) produced by the root pathogen Periconia circinata (Mangin) Sacc. was investigated. PC-toxin reproduces the effects of milo disease only in susceptible genotypes of sorghum and affects gene expression by enhancing the synthesis of specific mRNAs coding for a group of four 16 kD proteins (p16s). The p16s were purified by preparative two-dimensional polyacrylamide gel electrophoresis and each protein was characterized by cleavage and mapping of the resulting peptides. The peptides produced by cleavage of each of the p16s were indistinguishable in one-dimensional polyacrylamide gels, suggesting that the p16s have very similar compositions. Polyclonal antibodies produced against the combined purified p16s cross-reacted with 16 kD proteins in extracts from all six graminaceous species tested and with monocots in two other families but not with proteins from the six dicot species analyzed. The p16s in the sorghum plant were detected by Western blot analysis of protein extracts of various organs. The p16s were distributed throughout the plant, but the content was greatest in roots and lower stalk and progressively decreased in leaves, peduncle, and inflorescence tissues. The p16s were localized in tissues by tissue printing. The p16s were detected in the epidermis of the lower stem and in the epidermis, cortex, and endodermis of lateral and buttress roots. The effect of an elicitor (CG-elicitor) prepared from the conidial matrix of Colletotrichum graminicola on P. circinata pathogenesis was investigated. Treatment of seedling roots with CG-elicitor preparations induced the synthesis of 3-deoxyanthocyanidin phytoalexins but did not protect seedlings against infection by toxin-producing isolates of P. circinata, nor did it prevent development of milo disease symptoms induced by subsequent treatment with PC-toxin. CG-elicitor inhibited root growth and enhanced the synthesis of p16 proteins but did not cause expression of milo disease symptoms.
Degree
Ph.D.
Advisors
Dunkle, Purdue University.
Subject Area
Botany|Biochemistry|Plant pathology
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