New Phytol. 2016 Sep 2
Hybrid necrosis is a common type of hybrid incompatibility in plants. This phenomenon is caused by deleterious epistatic interactions, resulting in spontaneous activation of plant defenses associated with leaf necrosis, stunted growth and reduced fertility in hybrids. Specific combinations of alleles of ACCELERATED CELL DEATH 6 (ACD6) have been shown to be a common cause of hybrid necrosis in Arabidopsis thaliana. Increased ACD6 activity confers broad-spectrum resistance against biotrophic pathogens but reduces biomass production. We generated 996 crosses among individuals derived from a single collection area around Tübingen (Germany) and screened them for hybrid necrosis. Necrotic hybrids were further investigated by genetic linkage, amiRNA silencing, genomic complementation and metabolic profiling. Restriction site associated DNA (RAD)-sequencing was used to understand genetic diversity in the collection sites containing necrosis-inducing alleles. Novel combinations of ACD6 alleles found in neighbouring stands were found to activate the A. thaliana immune system. In contrast to what we observed in controlled conditions, necrotic hybrids did not show reduced fitness in the field. Metabolic profiling revealed changes associated with the activation of the immune system in ACD6-dependent hybrid necrosis. This study expands our current understanding of the active role of ACD6 in mediating trade-offs between defense responses and growth in A. thaliana.
We also celebrated the three freshly minted PhD graduates, Diep Tran (starting as a postdoc with Lionel Navarro at the ENS in Paris), Jorge Kageyama (starting as a postdoc with Barbara Treutlein at the MPI-EVA in Leipzig) and Cris Zaidem (starting in 2017 as a postdoc with Michael Purugganan at NYU)
Polina Yu Novikova, Nora Hohmann, Viktoria Nizhynska, Takashi Tsuchimatsu, Jamshaid Ali, Graham Muir, Alessia Guggisberg, Tim Paape, Karl Schmid, Olga M Fedorenko, Svante Holm, Torbjörn Säll, Christian Schlötterer, Karol Marhold, Alex Widmer, Jun Sese, Kentaro K Shimizu, Detlef Weigel, Ute Krämer, Marcus A Koch & Magnus Nordborg
The notion of species as reproductively isolated units related through a bifurcating tree implies that gene trees should generally agree with the species tree and that sister taxa should not share polymorphisms unless they diverged recently and should be equally closely related to outgroups. It is now possible to evaluate this model systematically. We sequenced multiple individuals from 27 described taxa representing the entire Arabidopsis genus. Cluster analysis identified seven groups, corresponding to described species that capture the structure of the genus. However, at the level of gene trees, only the separation of Arabidopsis thaliana from the remaining species was universally supported, and, overall, the amount of shared polymorphism demonstrated that reproductive isolation was considerably more recent than the estimated divergence times. We uncovered multiple cases of past gene flow that contradict a bifurcating species tree. Finally, we showed that the pattern of divergence differs between gene ontologies, suggesting a role for selection.
September 26, 3 pm
MPH Lecture Hall
October 5, 3 pm
Room 7E02, Uni - Hörsaalzentrum
October 10, 1 pm
Room 7E02, Uni - Hörsaalzentrum