Activation of defense mechanism in wheat by polyphenol oxidase from aphid saliva.
The saliva of two cereal aphids, Sitobion avenae and Schizaphis graminum in third-instar nymphs, was collected after 24 h of feeding by 30 aphids, separately, on artificial diet sachets, and the salivary enzymes were determined. The result showed that polyphenol oxidase (PPO) existed in the saliva of both aphid species, and the enzymatic activities were 6.2 x 10(-3) U/g for S. avenae and 2.37 x 10(-1) U/g for S. graminum, revealing a 38-fold higher activity in the saliva of S. graminum than in the saliva of S. avenae. It was speculated that the higher PPO activity in S. graminum saliva was a contributing factor to the light yellow spot left on the feeding site of the wheat leaf by S. graminum; no such spot was left by S. avenae. After treatment of a wheat seedling with the saliva of S. avenae and S. graminum and PPO at the concentration of aphid saliva, transcript profiling data showed that aphid saliva and PPO significantly induced expression of the genes aos and fps. Because genes aos and fps encode the key enzymes in the defense signal pathways jasmonic acid and terpene signal pathways, respectively, it was deduced that PPO from aphid saliva, as the main elicitor, triggers an appropriate defense response in wheat through jasmonic acid and terpene signal pathways.
Ma
Rui
R
The State Key Laboratory for Biology of Plant Diseases of Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, People's Republic of China.
Chen
Ju-Lian
JL
Cheng
Deng-Fa
DF
Sun
Jing-Rui
JR
D000821:Animal Feed; D000818:Animals; D001042:Aphids / Q000201:enzymology*; D003517:Cyclopentanes / Q000378:metabolism; D017931:DNA Primers; D018744:DNA, Plant / Q000235:genetics; D007113:Immunity, Innate / Q000502:physiology; D014442:Monophenol Monooxygenase / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D054883:Oxylipins / Q000378:metabolism; D018515:Plant Leaves / Q000469:parasitology; D018749:RNA, Plant / Q000235:genetics / Q000302:isolation & purification; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012463:Saliva / Q000201:enzymology*; D015398:Signal Transduction; D013729:Terpenes / Q000378:metabolism; D014908:Triticum / Q000187:drug effects / Q000235:genetics / Q000276:immunology / Q000469:parasitology*
D003517:Cyclopentanes; D017931:DNA Primers; D018744:DNA, Plant; D054883:Oxylipins; D018749:RNA, Plant; D012337:RNA, Ribosomal, 18S; D013729:Terpenes; C011006:jasmonic acid; D014442:Monophenol Monooxygenase