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1.  Resistance to sap-sucking insects in modern-day agriculture 
Plants and herbivores have co-evolved in their natural habitats for about 350 million years, but since the domestication of crops, plant resistance against insects has taken a different turn. With the onset of monoculture-driven modern agriculture, selective pressure on insects to overcome resistances has dramatically increased. Therefore plant breeders have resorted to high-tech tools to continuously create new insect-resistant crops. Efforts in the past 30 years have resulted in elucidation of mechanisms of many effective plant defenses against insect herbivores. Here, we critically appraise these efforts and – with a focus on sap-sucking insects – discuss how these findings have contributed to herbivore-resistant crops. Moreover, in this review we try to assess where future challenges and opportunities lay ahead. Of particular importance will be a mandatory reduction in systemic pesticide usage and thus a greater reliance on alternative methods, such as improved plant genetics for plant resistance to insect herbivores.
doi:10.3389/fpls.2013.00222
PMCID: PMC3694213  PMID: 23818892
phloem-feeding insects; crop pests; breeding; genetically modified crops; natural insecticides
2.  Lipoxygenase-mediated modification of insect elicitors 
Plant Signaling & Behavior  2010;5(12):1674-1676.
Plants can distinguish mechanical damage from larval folivory through the recognition of specific constituents of larval oral secretions (OS) which are deposited on the surface of leaf wounds during feeding. Fatty acid-amino acid conjugates (FACs) are major constituents of the OS of Lepidopteran larvae and they are strong elicitors of herbivore-induced defense responses in several plant species, including the wild tobacco Nicotiana attenuata. When OS from Manduca sexta larvae is deposited on N. attenuata wounded leaves, the major FAC N-linolenoyl-glutamic acid (18:3-Glu) is modified within seconds by a heat labile process. Some of the major modified forms are oxygenated products derived from 13-lipoxygenase activity and one of these derivatives, 13-oxo-13:2-Glu, is an active elicitor of enhanced JA biosynthesis and differential monoterpene emission in N. attenuata leaves.
doi:10.4161/psb.5.12.14036
PMCID: PMC3115133  PMID: 21150262
lipoxygenase; plant-insect interactions; fatty acid-amino acid conjugates; FAC; fatty acid-amides; insect elicitor; jasmonic acid; volatiles; herbivore-associated-elicitors; HAEs
3.  Rapid modification of the insect elicitor N-linolenoyl-glutamate via a lipoxygenase-mediated mechanism on Nicotiana attenuata leaves 
BMC Plant Biology  2010;10:164.
Background
Some plants distinguish mechanical wounding from herbivore attack by recognizing specific constituents of larval oral secretions (OS) which are introduced into plant wounds during feeding. Fatty acid-amino acid conjugates (FACs) are major constituents of Manduca sexta OS and strong elicitors of herbivore-induced defense responses in Nicotiana attenuata plants.
Results
The metabolism of one of the major FACs in M. sexta OS, N-linolenoyl-glutamic acid (18:3-Glu), was analyzed on N. attenuata wounded leaf surfaces. Between 50 to 70% of the 18:3-Glu in the OS or of synthetic 18:3-Glu were metabolized within 30 seconds of application to leaf wounds. This heat-labile process did not result in free α-linolenic acid (18:3) and glutamate but in the biogenesis of metabolites both more and less polar than 18:3-Glu. Identification of the major modified forms of this FAC showed that they corresponded to 13-hydroxy-18:3-Glu, 13-hydroperoxy-18:3-Glu and 13-oxo-13:2-Glu. The formation of these metabolites occurred on the wounded leaf surface and it was dependent on lipoxygenase (LOX) activity; plants silenced in the expression of NaLOX2 and NaLOX3 genes showed more than 50% reduced rates of 18:3-Glu conversion and accumulated smaller amounts of the oxygenated derivatives compared to wild-type plants. Similar to 18:3-Glu, 13-oxo-13:2-Glu activated the enhanced accumulation of jasmonic acid (JA) in N. attenuata leaves whereas 13-hydroxy-18:3-Glu did not. Moreover, compared to 18:3-Glu elicitation, 13-oxo-13:2-Glu induced the differential emission of two monoterpene volatiles (β-pinene and an unidentified monoterpene) in irlox2 plants.
Conclusions
The metabolism of one of the major elicitors of herbivore-specific responses in N. attenuata plants, 18:3-Glu, results in the formation of oxidized forms of this FAC by a LOX-dependent mechanism. One of these derivatives, 13-oxo-13:2-Glu, is an active elicitor of JA biosynthesis and differential monoterpene emission.
doi:10.1186/1471-2229-10-164
PMCID: PMC3095298  PMID: 20696061

Results 1-3 (3)