A secreted Ustilago maydis effector promotes virulence by targeting anthocyanin biosynthesis in maize.

The biotrophic fungus Ustilago maydis causes smut disease in maize with characteristic tumor formation and anthocyanin induction. Here, we show that anthocyanin biosynthesis is induced by the virulence promoting secreted effector protein Tin2. Tin2 protein functions inside plant cells where it interacts with maize protein kinase ZmTTK1. Tin2 masks a ubiquitin-proteasome degradation motif in ZmTTK1, thus stabilizing the active kinase. Active ZmTTK1 controls activation of genes in the anthocyanin biosynthesis pathway. Without Tin2, enhanced lignin biosynthesis is observed in infected tissue and vascular bundles show strong lignification. This is presumably limiting access of fungal hyphae to nutrients needed for massive proliferation. Consistent with this assertion, we observe that maize brown midrib mutants affected in lignin biosynthesis are hypersensitive to U. maydis infection. We speculate that Tin2 rewires metabolites into the anthocyanin pathway to lower their availability for other defense responses. DOI: http://dx.doi.org/10.7554/eLife.01355.001.

Electrophysiological correlates of encoding and retrieving emotional events.

This study examined the impact of emotional content on encoding and retrieval processes. Event-related potentials were recorded in a source recognition memory task. During encoding, a posterior positivity for positive and negative pictures (250-450 ms) that presumably reflects attentional capturing of emotionally valenced stimuli was found. Additionally, positive events, which were also rated as less arousing than negative events, gave rise to anterior and posterior slow wave activity as compared with neutral and negative events and also showed enhanced recognition memory. It is assumed that positive low-arousing events enter controlled and elaborated encoding processes that are beneficial for recognition memory performance. The high arousal of negative events may interfere with controlled encoding mechanisms and attenuate item recognition and the quality of remembering. Moreover, topographically distinct late posterior negativities were obtained for the retrieval of the context features location and time that support the view that this component reflects processes in service of reconstructing the study episode by binding together contextual details with an item and that varies with the kind of episodic detail to be retrieved.