title: Feeding of Whitefly on Tobacco Decreases Aphid Performance via Increased Salicylate Signaling.
abstract: BACKGROUND
  The feeding of Bemisia tabaci nymphs trigger the SA pathway in some plant species. A previous study showed that B. tabaci nymphs induced defense against aphids (Myzus persicae) in tobacco. However, the mechanism underlying this defense response is not well understood.
  
  
  RESULTS
  Here, the effect of activating the SA signaling pathway in tobacco plants through B. tabaci nymph infestation on subsequent M. persicae colonization is investigated. Performance assays showed that B. tabaci nymphs pre-infestation significantly reduced M. persicae survival and fecundity systemically in wild-type (WT) but not salicylate-deficient (NahG) plants compared with respective control. However, pre-infestation had no obvious local effects on subsequent M. persicae in either WT or NahG tobacco. SA quantification results indicated that the highest accumulation of SA was induced by B. tabaci nymphs in WT plants after 15 days of infestation. These levels were 8.45- and 6.14-fold higher in the local and systemic leaves, respectively, than in controls. Meanwhile, no significant changes of SA levels were detected in NahG plants. Further, biochemical analysis of defense enzymes polyphenol oxidase (PPO), peroxidase (POD), β-1,3-glucanase, and chitinase demonstrated that B. tabaci nymph infestation increased these enzymes' activity locally and systemically in WT plants, and there was more chitinase and β-1, 3-glucanase activity systemically than locally, which was opposite to the changing trends of PPO. However, B. tabaci nymph infestation caused no obvious increase in enzyme activity in any NahG plants except POD.
  
  
  CONCLUSIONS
  In conclusion, these results underscore the important role that induction of the SA signaling pathway by B. tabaci nymphs plays in defeating aphids. It also indicates that the activity of β-1, 3-glucanase and chitinase may be positively correlated with resistance to aphids.
authors.affiliation: Shandong Provincial Key Laboratory for Biology of Vegetable Diseases and Insect Pests, College of Plant Protection, Shandong Agricultural University, Tai'an, Shandong, China.
authors.forename: Haipeng
authors.initials: H
authors.lastname: Zhao
authors.affiliation: Shandong Provincial Key Laboratory for Biology of Vegetable Diseases and Insect Pests, College of Plant Protection, Shandong Agricultural University, Tai'an, Shandong, China; Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, Yunnan, China.
authors.forename: Xiaoying
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Shandong Provincial Key Laboratory for Biology of Vegetable Diseases and Insect Pests, College of Plant Protection, Shandong Agricultural University, Tai'an, Shandong, China.
authors.forename: Ming
authors.initials: M
authors.lastname: Xue
authors.affiliation: Shandong Provincial Key Laboratory for Biology of Vegetable Diseases and Insect Pests, College of Plant Protection, Shandong Agricultural University, Tai'an, Shandong, China.
authors.forename: Xiao
authors.initials: X
authors.lastname: Zhang
mesh_terms: D000818:Animals; D001042:Aphids; D002688:Chitinases / Q000378:metabolism; D043326:Glucan 1,3-beta-Glucosidase / Q000378:metabolism; D006430:Hemiptera; D018515:Plant Leaves / Q000378:metabolism / Q000469:parasitology; D020156:Salicylic Acid / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D014026:Nicotiana / Q000378:metabolism* / Q000469:parasitology
chemical_list: D002688:Chitinases; D043326:Glucan 1,3-beta-Glucosidase; D020156:Salicylic Acid