Enhanced expression and activation of the alternative oxidase during infection of Arabidopsis with Pseudomonas syringae pv tomato.
Cyanide-resistant ("alternative") respiration was studied in Arabidopsis during incompatible and compatible infection with Pseudomonas syringae pv tomato DC3000. Total leaf respiration increased as the leaves became necrotic, as did the cyanide-resistant component that was sensitive to salicylhydroxamic acid. Infiltration of leaves with an avirulent strain rapidly induced alternative oxidase (AOX) mRNA, whereas the increase was delayed in the compatible combination. The increase in mRNA correlated with the increase in AOX protein. Increased expression was confined to the infected leaves, in contrast to the pathogenesis-related protein-1, which was induced systemically. Virtually all of the AOX protein was in the reduced (high-activity) form. Using transgenic NahG and mutant npr1-1 and etr1-1 plants, we established that the rapid induction of the AOX was associated with necrosis and that ethylene, but not salicylic acid, was required for its induction. Increased pyruvate levels in the infected leaves suggested that increased substrate levels were respired through the alternative pathway; however, in the control leaves and the infected leaves, respiration was not inhibited by salicylhydroxamic acid alone. Increased respiration appeared to be associated primarily with symptom expression rather than resistance reactions.
Simons
B H
BH
Graduate School of Functional Ecology, Department of Plant Ecology and Evolutionary Biology, Section of Plant Pathology, Utrecht University, The Netherlands.
Millenaar
F F
FF
Mulder
L
L
Van Loon
L C
LC
Lambers
H
H
D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000382:microbiology*; D003486:Cyanides / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D005030:Ethylenes / Q000378:metabolism; D015870:Gene Expression; D007150:Immunohistochemistry; D024101:Mitochondrial Proteins; D010088:Oxidoreductases / Q000235:genetics* / Q000378:metabolism*; D010101:Oxygen Consumption / Q000187:drug effects; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins; D011549:Pseudomonas / Q000472:pathogenicity; D019289:Pyruvic Acid / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D020156:Salicylic Acid / Q000494:pharmacology; D014774:Virulence; D000099188:Alternative Oxidase
D003486:Cyanides; D005030:Ethylenes; D024101:Mitochondrial Proteins; D010088:Oxidoreductases; D010940:Plant Proteins; D019289:Pyruvic Acid; D012333:RNA, Messenger; D018749:RNA, Plant; D020156:Salicylic Acid; D000099188:Alternative Oxidase; C036216:ethylene