Final Report Summary - INDUCED DEFENCE (Herbivore induced plant defences: the evolution and genetic basis of their specificity)
Plants have been threatened by insect herbivores for more than 350 million years. During their struggle for survival, plants have evolved many sophisticated anti-herbivore defence strategies, ranging from physical barriers to toxins and antifeedants. Because defence in plants is costly, induced defence was suggested to have evolved as a means of reducing these costs. Induced defence is widespread in plants and its importance has been widely accepted by ecologists and biologists.
Herbivore induced defences are likely to be species-specific. The specificity has been suggested to be mediated by herbivore associated elicitors (HAE), however, how such specificity evolved and what mechanisms are involved remain unknown. This project had two specific objectives: 1) to investigate the evolution of specificity in HAE-induced plant defences; and 2) to identify the genetic basis of the specificity in HAE-induced plant defence.
For the first objective, a comparative approach was used to investigate the induced defences among closely related Nicotiana species and elicitors from different insect oral secretions. The results showed that HAE-induced defences are highly specific among closely related Nicotiana species from three perspectives: 1) single Nicotiana species can elicit distinct responses to different HAEs; 2) one HAE can induce different defence responses among closely related Nicotiana species; 3) the effect of HAE-induced defences differ for the Solanaceae specialist M. sexta and the generalist S. littoralis.
For the second objective, the leaf transcriptomes of six Nicotiana species that were induced by different HAEs were sequenced (in total 60 RNA-seq libraries), and a key co-expression network was identified, which correlates with the specificity of HAE-induced defences in Nicotiana, both within species and between species. Functional analysis revealed that the identified co-expression network is indeed involved in HAE-induced early defence signalling. To understand the evolution of the identified co-expression network, a phylogenomics approach was used. The results showed that whole genome duplication events in Solanaceae contributed to the evolution of HAE-induced early signalling network in Nicotiana.
Although the IEF project funding is finished, Dr. Xu and his team will continue to work on the research direction and system developed during the IEF. Several new projects that aim at characterizing the function of individual genes in the co-expression network are ongoing. The newly identify herbivore induced early defense signalling network has paved the way for further explorations of the mechanisms and evolution of herbivore induced defences in plants. The identified herbivore induced co-expression network and the finding that genome-wide duplication significantly influences the evolution of herbivore induced defences may provide useful information for crop breeding. In addition, the new methods developed in the project are expected to be used by other researchers to rapidly identify genes involved in complex traits.
Herbivore induced defences are likely to be species-specific. The specificity has been suggested to be mediated by herbivore associated elicitors (HAE), however, how such specificity evolved and what mechanisms are involved remain unknown. This project had two specific objectives: 1) to investigate the evolution of specificity in HAE-induced plant defences; and 2) to identify the genetic basis of the specificity in HAE-induced plant defence.
For the first objective, a comparative approach was used to investigate the induced defences among closely related Nicotiana species and elicitors from different insect oral secretions. The results showed that HAE-induced defences are highly specific among closely related Nicotiana species from three perspectives: 1) single Nicotiana species can elicit distinct responses to different HAEs; 2) one HAE can induce different defence responses among closely related Nicotiana species; 3) the effect of HAE-induced defences differ for the Solanaceae specialist M. sexta and the generalist S. littoralis.
For the second objective, the leaf transcriptomes of six Nicotiana species that were induced by different HAEs were sequenced (in total 60 RNA-seq libraries), and a key co-expression network was identified, which correlates with the specificity of HAE-induced defences in Nicotiana, both within species and between species. Functional analysis revealed that the identified co-expression network is indeed involved in HAE-induced early defence signalling. To understand the evolution of the identified co-expression network, a phylogenomics approach was used. The results showed that whole genome duplication events in Solanaceae contributed to the evolution of HAE-induced early signalling network in Nicotiana.
Although the IEF project funding is finished, Dr. Xu and his team will continue to work on the research direction and system developed during the IEF. Several new projects that aim at characterizing the function of individual genes in the co-expression network are ongoing. The newly identify herbivore induced early defense signalling network has paved the way for further explorations of the mechanisms and evolution of herbivore induced defences in plants. The identified herbivore induced co-expression network and the finding that genome-wide duplication significantly influences the evolution of herbivore induced defences may provide useful information for crop breeding. In addition, the new methods developed in the project are expected to be used by other researchers to rapidly identify genes involved in complex traits.