Trade-offs between the accumulation of cuticular wax and jasmonic acid-mediated herbivory resistance in maize

Plants have evolved complex physical and chemical defense systems that allow them to withstand herbivory infestation.Composed of a complex mixture of very-long-chain fatty acids(VLCFAs)and their derivatives,cuticular wax constitutes the first physical line of defense against herbivores.Here,we report the function of Glossy 8(ZmGL8),which encodes a 3-ketoacyl reductase belonging to the fatty acid elongase complex,in orchestrating wax production and jasmonic acid(JA)-mediated defenses against herbivores in maize(Zea mays).The mutation of GL8 enhanced chemical defenses by activating the JA-dependent pathway.We observed a trade-off between wax accumulation and JA levels across maize glossy mutants and 24 globally collected maize inbred lines.In addition,we demonstrated that mutants defective in cuticular wax biosynthesis in Arabidopsis thaliana and maize exhibit enhanced chemical defenses.Comprehensive transcriptomic and lipidomic analyses indicated that the gl8 mutant confers chemical resistance to herbivores by remodeling VLCFA-related lipid metabolism and subsequent JA biosynthesis and signaling.These results suggest that VLCFA-related lipid metabolism has a critical role in regulating the trade-offs between cuticular wax and JA-mediated chemical defenses.

Contrasting Effects of Ethylene Biosynthesis on Induced Plant Resistance against a Chewing and a Piercing-Sucking Herbivore in Rice

Ethylene is a stress hormone with contrasting whether these differences are plant- or herbivore-specific. effects on herbivore resistance. However, it remains unknown We cloned a rice 1-aminocyclopropane-l-carboxylic acid （ACC） synthase gene, OsACS2, whose transcripts were rapidly up-regulated in response to mechanical wounding and infestation by two important pests： the striped stem borer （SSB） Chilo suppressalis and the brown planthopper （BPH） Nilaparvata lugens. Antisense expression of OsACS2 （as-acs） reduced elicited ethylene emission, SSB-elicited trypsin protease inhibitor （TrypPI） activity, SSB-induced volatile release, and SSB resistance. Exogenous application of ACC restored TrypPI activity and SSB resistance. In contrast to SSB, BPH infestation increased volatile emission in as-acs lines. Accordingly, BPH preferred to feed and oviposit on wild-type （WT） plants--an effect that could be attributed to two repellent volatiles, 2-hep- tanone and 2-heptanol, that were emitted in higher amounts by as-acs plants. BPH honeydew excretion was reduced and natural enemy attraction was enhanced in as-acs lines, resulting in higher overall resistance to BPH. These results demonstrate that ethylene signaling has contrasting, herbivore-specific effects on rice defense responses and resistance against a chewing and a piercing-sucking insect, and may mediate resistance trade-offs between herbivores of different feeding guilds in rice.

To eat or not to eat-relationship of lichen herbivory by snails with secondary compounds and field frequency of lichens

Aims The biochemical defense of lichens against herbivores and its rela-tionship to lichen frequency are poorly understood.Therefore,we tested whether chemical compounds in lichens act as feeding defense or rather as stimulus for snail herbivory among lichens and whether experimental feeding by snails is related to lichen fre-quency in the field.Methods In a no-choice feeding experiment,we fed 24 lichen species to snails of two taxa from the Clausilidae and Enidae families and compared untreated lichens and lichens with compounds removed by acetone rinsing.Then,we related experimental lichen consump-tion with the frequency of lichen species among 158 forest plots in the field(schwäbische alb,germany),where we had also sampled snail and lichen species.Important findings In five lichen species,snails preferred treated samples over untreated controls,indicating chemical feeding defense,and vice versa in two species,indicating chemical feeding stimulus.Interestingly,com-pared with less frequent lichen species,snails consumed more of untreated and less of treated samples of more frequent lichen spe-cies.removing one outlier species resulted in the loss of a significant positive relationship when untreated samples were analyzed separately.However,the interaction between treatment and lichen frequency remained significant when excluding single species or including snail genus instead of taxa,indicating that our results were robust and that lumping the species to two taxa was justified.our results imply lichen-feeding snails to prefer frequent lichens and avoid less frequent ones because of secondary compound rec-ognition.This supports the idea that consumers adapt to the most abundant food source.