In contrast to direct defenses, how indirect defenses function chemically is well understood. JA elicitation and herbivore attack from 4 different species of insects not mechanical wounding cause plants to systemically release a bouquet of mono-and sesquiterpenes, in addition to the green leaf volatiles that are primarily released from the wounded leaves Figure 1.
The volatile release has been verified in plants grown in native populations, where it functions as an indirect defense in two distinct ways. The volatile release attracts predatory bugs to Manduca eggs and feeding larvae, dramatically increasing predation rates.
Second, the volatile release decreases oviposition rates from adult moths. These ovipositing adults are likely relying on the volatile release to identify host plants without competitors a single Manduca larvae requires many host plants to complete development and to avoid plants on which predators are probably present.
By synthesizing single components of the herbivore-induced volatile bouquet and applying them to unattacked plants in quantities naturally emitted, it was demonstrated that individual components from all three major biosynthetic pathways contributing to the volatile bouquet, namely a monoterpene linalool , a sesquiterpene bergamotene , and a green leaf volatile cis-3 hexenanol.
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Each actively attracted predatory bugs. The observation that enhancing the release of single components of the complex blend was sufficient to attract predators in nature makes the engineering of this type of indirect defense in crop plants, perhaps in conjunction with direct defenses, a tractable proposition.
A Wounding of the leaf tissue results in a jasmonic acid burst, which is amplified by caterpillar feeding and the application of FACs from larval oral secretions to the wound. C Caterpillar feeding and the application of their oral secretions to wounds cause an ethylene burst that D attenuates the wound- and jasmonic acid-induced accumulation of nicotine by suppressing the accumulation of transcripts for a key regulatory step in nicotine biosynthesis pmt : putresine N-methyl transferase. The attenuation of the direct defense, nicotine, may be an adaptation to the feeding of a specialized herbivore that is able to tolerate high alkaloid concentrations and can potentially use them for its own defense.
This reconfiguration consists of three temporal and spatial alterations. Addition of FACs antagonizes the wound-induced increase W of transcripts encoding threonine deaminase TD , representing a type-I expression pattern that spreads systemically throughout the plant from the wound site.
The wound-induced increase in transcripts in a type-IIa expression pattern exemplified by PIOX: pathogen-induced peroxidase is further amplified after application of FACs to wounds. In contrast, the genes with a type-IIb expression pattern are suppressed after wounding and further suppressed with the addition of FACs, as exemplified by the gene encoding the light harvesting complex subunit LHB C1.
Baldwin  Plant responses to insect herbivory: The emerging molecular analysis. Annual Review of Plant Biology in press. When attacked by the nicotine-tolerant tobacco specialist, M. Sexta Figure 1 , N. The induced increase in JA levels that is normally proportional to the amount of mechanical wounding erupts into a JA burst that increases concentrations 2—10 times those of wound-induced levels and is propagated throughout the damaged leaf ahead of the rapidly foraging herbivore.
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Wounding and JA-elicitation do not result in ethylene emissions, but an M. The ethylene burst suppresses the wound- and JA- induced accumulation of nicotine biosynthetic genes, NaPMT1 and 2 , and the associated nicotine accumulations. The ethylene burst does not suppress the volatile release. Manduca attack, therefore, down-regulates a major direct defense, nicotine, while up-regulating an indirect defense, the volatile release Figure 1. Applying larval oral secretions and regurgitants to mechanical wounds can mimic all of the Manduca -induced changes in N.
A suite of 8 fatty acid amino acid conjugates FACs; Figure 1 in the oral secretions is necessary and sufficient for not only the transcriptional changes mentioned below but also the JA burst and the volatile release. If these FACs are removed from the oral secretions by ion-exchange chromatography, eliciting activity is lost and regained when synthetic FACs are added back to the ion-exchanged, inactive, oral secretions.
Since the oral secretions of other tobacco-feeding insects e.
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Heliothis virescens also elicited similar changes in wound-induced mRNA, maybe all tobacco feeding lepidoptera are "recognized" by a similar suite of FACs. In addition to the changes in defense phenotype after an M. DDRT-PCR was used to gain an unbiased view of the transcriptional changes, and from this study, it was estimated that more than genes respond to an herbivore attack. The herbivore-regulated genes could be crudely classified as being related to photosynthesis, electron transport, cytoskeleton, carbon and nitrogen metabolism, signaling, and a group responding to stress, wounding, or invasion of pathogens.
Overall, transcripts involved in photosynthesis were strongly down-regulated, while those responding to stress, wounding, and pathogens, and involved in shifting carbon and nitrogen to defense were strongly up-regulated.
To separate the wound-induced changes from the changes elicited by the M. Regurgitant modified the wound-induced responses by suppressing wound-induced transcripts systemically in the plant type I or amplifying the wound response in the attacked leaves type II. This amplification was either a down-regulation of wound-suppressed transcripts type IIb or an up-regulation of wound-increased transcripts type IIa Figure 1. Interestingly, all three patterns of Manduca -induced transcriptional changes of N.
The amounts of FACs required are so small that they may be transferred to the plant during normal feeding. These coordinated changes point to the existence of central herbivore-activated regulators of metabolism, which in turn are activated by minute amounts of FACs in Manduca's oral secretions.
Identification of these putative trans-activating factors would provide important insights into how plants recognize and coordinate their metabolic responses to an herbivore attack. The significance of this research is that a plant's ecological interactions are played out in an arena that is larger than the plant itself and as indirect defenses so clearly illustrate, incorporates many community-level components. Synecoculture is designed on a variety of environmental responses within ecological optimum in high-density mixed polyculture where various edible species were intentionally introduced.
The whole methodology can be considered as anthropogenic augmentation of ecosystem functioning that promotes dynamic biodiversity—productivity relationship prevalent in natural ecosystems. In this review we summarize the theoretical foundation to provide a systematic definition of synecoculture and clarify the relationship with existing farming methods. We also collate previously reported analyses of organic and mineral components in farm products, and outline their physiological characteristics and functions in response to culture environments.
Plant tissue culture letters. Already have an account? Login in here. Plant Biotechnology. Journal home Advance online publication Journal issue About the journal.
Synecological farming: Theoretical foundation on biodiversity responses of plant communities. Masatoshi Funabashi Author information. Keywords: community ecology , ecological optimum , physiological optimum , secondary metabolites , sustainable agriculture. Browse "Advance Publication" version.