General Understanding of Two-component Signal Transduction System

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(A): According to the well-documented scenario with regard to the cytokinin-mediated phosphorelay signal transduction in Arabidopsis thaliana, certain members of the type-B ARR family are crucially implicated in the regulatory networks that are primarily propagated by the cytokinin-receptors (AHKs) in response to cytokinin. Here we focused on a pair of highly homologous ARR10 and ARR12 genes by constructing an appropriate arr10 and arr12 double null mutant. The results suggested (A) that ARR10 and ARR12 are the prominent players that act redundantly in the AHK-dependent cytokinin signaling in roots.(B) : In Arabidopsis thaliana, the flowering time is regulated through the circadian clock that measures day-length and modulates the photoperiodic CO-FT output pathway in accordance to the external coincidence model. Nevertheless, little is known about the genetic linkage between the major clock associated TOCJ, CCAI, and LHY genes and the . canonical CO-FT flowering pathway. By employing a … More set of mutants including an extremely early flowering tocl ccal thy triple mutant, here we showed that CCAI and LHY act redundantly as negative regulators for the photoperiodic flowering pathway. The results of this study suggested that the circadian clock might open an exit for a photoperiodic output pathway during daytime.(C) : For a model filamentous fungi, Aspergillus nidulans, here we first compiled a whole list of His-Asp phosphorelay components, uncovering 15 genes for His-kinase (HK), 4 genes for response regulator (RR), and only one for histidine-containing phosphotransfer intermediate (HPt) . For all of these RR genes, a set of deletion mutants was constructed so as to create a null allele for each. When examined these mutant strains, two of them (designated as AsskA and AsrrA) showed a marked phenotype of hypersensitivity to oxidative stresses (particularly, hydrogen peroxide) .These results together are indicative of a physiological importance of the His-Asp phosphorelay signaling network involving the SskA and SrrA response regulators. Less