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Valim J.O.S.,Federal University of Sao Joao del Rei | Teixeira N.C.,Federal University of Sao Joao del Rei | Santos N.A.,Federal University of Sao Joao del Rei | Oliveira M.G.A.,Federal University of Vicosa | And 3 more authors.
Arthropod-Plant Interactions | Year: 2016

An initial destabilization of functions triggered by drought stress in plants is followed by acclimatization and acquisition of tolerance; however, knowledge remains limited on drought-mediated changes in plant quality for herbivores. We tested whether a water-stressed fast-growing plant negatively affects host-specialist insects in both sap-sucking and leaf-chewing feeding guilds. Collards (Brassica oleracea var. acephala) were grown in well-watered, slightly water-stressed and severely water-stressed conditions. Decreasing soil moisture adversely affected plant development, assessed as a reduction in leaf number and size, stomatal size and relative water content. Severely stressed plants had less fiber and glucosinolates; however, they showed more total nitrogen and lipids. Larval survival, pupal weight, reproductive rate (Ro) and rate of population growth (r) were lower when the leaf-chewing Plutella xylostella was reared with severely stressed collards. In multiple-choice tests, moths laid fewer eggs on leaf discs of collard that were exposed to drought. The fecundity of the sap-sucking Brevicoryne brassicae was higher and the development of alates was lower when insects were fed on plants kept in well-watered regime as compared to slight-stress and severe-stress. Despite higher nitrogen content and fewer glucosinolates, a higher level of leaf surface wax in severely stressed collards possibly decreased food quality for both herbivores. Thus, host-specific herbivores of different guilds showed similar responses to drought-stressed, fast-growing plants. Water-stressed crops could discourage the attack of specialist insects, but the intensity of the stress that is required to achieve this effect will greatly reduce crop production, in terms of plant growth or foliage increment. © 2016, Springer Science+Business Media Dordrecht.

Brustolini O.J.B.,Bioagro | Brustolini O.J.B.,National Institute of Science and Technology in Plant Pest Interactions | Machado J.P.B.,Bioagro | Machado J.P.B.,National Institute of Science and Technology in Plant Pest Interactions | And 17 more authors.
Plant Biotechnology Journal | Year: 2015

Begomovirus-associated epidemics currently threaten tomato production worldwide due to the emergence of highly pathogenic virus species and the proliferation of a whitefly B biotype vector that is adapted to tomato. To generate an efficient defence against begomovirus, we modulated the activity of the immune defence receptor nuclear shuttle protein (NSP)-interacting kinase (NIK) in tomato plants; NIK is a virulence target of the begomovirus NSP during infection. Mutation of T474 within the kinase activation loop promoted the constitutive activation of NIK-mediated defences, resulting in the down-regulation of translation-related genes and the suppression of global translation. Consistent with these findings, transgenic lines harbouring an activating mutation (T474D) were tolerant to the tomato-infecting begomoviruses ToYSV and ToSRV. This phenotype was associated with reduced loading of coat protein viral mRNA in actively translating polysomes, lower infection efficiency and reduced accumulation of viral DNA in systemic leaves. Our results also add some relevant insights into the mechanism underlying the NIK-mediated defence. We observed that the mock-inoculated T474D-overexpressing lines showed a constitutively infected wild-type transcriptome, indicating that the activation of the NIK-mediated signalling pathway triggers a typical response to begomovirus infection. In addition, the gain-of-function mutant T474D could sustain an activated NIK-mediated antiviral response in the absence of the virus, further confirming that phosphorylation of Thr-474 is the crucial event that leads to the activation of the kinase. © 2015 Society for Experimental Biology, Association of Applied Biologists and John Wiley & Sons Ltd.

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