Isolation and characterisation of a class of carbohydrate oxidases from higher plants, with a role in active defence.
In a search for novel plant-derived antimicrobial proteins, we screened extracts from salicylic acid (SA)-treated lettuce and sunflower leaves. These extracts displayed very potent antimicrobial activity against a set of phytopathogens. Characterisation of these extracts revealed that in both extracts, proteins of approximately 60 kDa were responsible for the antimicrobial activity. Further characterisation of these proteins and cloning of the respective cDNAs revealed close homology to a range of (plant) oxidases. Dissection of the enzymatic activity of both proteins revealed them to be carbohydrate oxidases (Helianthus annuus carbohydrate oxidase (Ha-CHOX) and Lactuca sativa carbohydrate oxidase (Ls-CHOX)) with broad substrate specificity and with hydrogen peroxide (H(2)O(2)) as one of the reaction products. The sunflower transcript, in addition to being SA inducible, was also inducible by fungal pathogens but not by ethylene and jasmonate. To determine whether Ha-CHOX plays a role in pathogen defence, it was transformed into tobacco and the effect of resistance to Pectobacterium carotovorum ssp. carotovorum was examined. Transgenic plants overexpressing Ha-CHOX displayed enhanced resistance to infection by this pathogen, and the resistance level was proportional to enzyme expression.
Custers
Jerôme H H V
JH
Syngenta Mogen B.V., Einsteinweg 97, 2333 CB Leiden, the Netherlands.
Harrison
Stuart J
SJ
Sela-Buurlage
Marianne B
MB
van Deventer
Els
E
Lageweg
Wessel
W
Howe
Peter W
PW
van der Meijs
Pieter J
PJ
Ponstein
Anne S
AS
Simons
Bert H
BH
Melchers
Leo S
LS
Stuiver
Maarten H
MH
D000595:Amino Acid Sequence; D004926:Escherichia coli / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D006368:Helianthus / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology; D006861:Hydrogen Peroxide / Q000378:metabolism; D018545:Lactuca / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology; D008969:Molecular Sequence Data; D016973:Pectobacterium carotovorum / Q000472:pathogenicity; D010802:Phylogeny; D018515:Plant Leaves / Q000737:chemistry; D010940:Plant Proteins / Q000737:chemistry / Q000302:isolation & purification*; D030821:Plants, Genetically Modified; D020156:Salicylic Acid / Q000494:pharmacology; D013379:Substrate Specificity; D014026:Nicotiana / Q000235:genetics / Q000382:microbiology; D014170:Transformation, Genetic
D010940:Plant Proteins; D006861:Hydrogen Peroxide; D020156:Salicylic Acid