Multi-phase Study Of Plant Defenses To Leafminer Damage

During the long time interactions with insects, plants have developed a sophisticated defense system. Healthy plants usually utilize constitutive defenses which always exist in plants, while they will express the inducible defense which reacts efficiently after being damaged by attackers. These two kinds of plant defense reflect the diversity of time course. Induced defense can be express at the attacked leaves (local defense) or undamaged leaves (systemic defense) of the plants; and they reflect the diversity of defense position. Not only that, all these defenses can be achieved by multiple pathways: Firstly, plants can defense the insects with noxious materials always existing in the plant directly (direct defense); secondly, damaged plants can also"communicate"with their healthy neighbors, and the healthy neighbors will prepare for damage and defense insects together (plant-plant communication); Thirdly, there are many enemies of herbivory insects in the nature, plants can attract the natural enemies that may help defense the insects (indirect defense).We used the"plant-leafminer-parasitoid"tritrophic systems to study 4 key points about plant defenses;1. Interactions between plants and insects——Transcription defense responses of Arabidopsis thaliana to leafminer damage.Leafminers, a kind of special insects which live inside the plants, have a different damage patterns from other insects. We use an affimetrix ATH1 arabisopsis microarray to test the transcription response pattern of Arabidopsis thaliana to pea leafminers damages, both locally infected leaves (LI) and systemically infected leaves (SI) were tested. The data proved that Arabidopsis thaliana response to pea leafminer was more similar with that of pathogens than other insects. The results support our hypothesis that the plant response patterns were greatly related to the attacker's damages patterns.2. Systemic defenses of new secondary leaves are stranger than old primary leaves in lima bean (Phaseolus lunatus).New secondary leaves often have different biological characters from the old primary leaves, and the new leaves are more vulnerability to herbivores. Whether the systemic defense abilities in secondary and primary leaves are different? Our researches showed that the new secondary leaves had stronger systemic defense ability then the old primary leaves, both in direct defense and in indirect defense. Thus, diverse parts plant has diverse defense abilities; the plant prefers to protect the new leaves when attacked.3. Systemic researches of"plant-plant communication"."Plant-plant communication"is a new and hot topic. Many studies have focused on this interesting topic. However, the mechanism of this phenomenon was not clearly known. Firstly, we demonstrated that communication of plants was nonrelated to the phylogenetic relationship of different species, while the character of volatiles was a crucial factor; secondly, the VOCs that emitters released is the"words"between plants, and different kind of volatiles have different characters; thirdly, we analyzed the response of Arabidopsis thaliana signal pathway in detail; finally, Arabidopsis thaliana mutant was used to disclose that ethylene response signal of plant was indispensable in"plant-plant communication". Our results gave a whole and clear picture of plant-plant communication between lima bean and Arabidopsis thaliana.4. Rhythm interactions in tritrophic system.Diurnal rhythm is a basic character of organisms, which can be controlled by inherent circadian clock or affected by other factors. However, whether the rhythms of different organisms can interact with each other is poorly known. Here, we used the"lima bean-leafminer-parasitoid"tritrophic systems to answer this question. The results showed that the rhythms in the tritrophic system were synchronized with each other, but this can be disturbed by dark, which indicated that the rhythm interactions in the tritrophic system was the result of co-evolution under natural light-dark cycle. We also found that naive and oviposition-experienced parasitoids were able to respectively utilize the volatile rhythm information from the damaged plant to locate host leafminers.We hope that our results can help us understand more about plant defense phenomenon and mechanisms, which may guide pest controlling in the agriculture.