The function of an autonomous pathway component in flowering time control in Arabidopsis and barley
The circadian clock regulated glycine-rich RNA-binding protein AtGRP7 (Arabidopsis thaliana gylcine-rich RNA binding protein 7) promotes floral transition in the long day plant Arabidopsis thaliana. We will compare the role of this glycine-rich RNA-binding protein in flowering time (FTi) control in Arabidopsis thaliana and the role of a homologue, HvGR-RBP1 in Hordeum vulgare. AtGRP7 is associated with several of the known flowering pathways in Arabidopsis. Global profiling of small RNAs by RNA-seq identified a suite of miRNAs including miRNAs associated with FTi control that were differentially expressed in AtGRP7-ox plants vs. wt plants. While the level of these miRNAs was reduced in AtGRP7-ox plants, the levels of the corresponding precursors were elevated, indicating that AtGRP7 affects the processing of microRNA precursor transcripts. In line with this, we could show that AtGRP7 interacts with pri-miRNAs in vivo. We will investigate in detail the impact of AtGRP7 on these FTi-related miRNAs during floral transition. The relevance of the miRNAs and their corresponding targets for the effect of AtGRP7 on FTi will be investigated. Furthermore, we will monitor differences in expression of other types of small RNAs including siRNAs in plants with altered AtGRP7 level during floral transition. In barley, we have obtained TILLING lines with mutations in HvGR-RBP1. We will characterize the flowering behaviour of these lines both in defined light-dark cycles and in the field. Furthermore, we will take a candidate gene approach to identify potential downstream targets of HvGR-RBP1 including FTi related miRNAs and provide insights into the signalling pathways through which HvGR-RBP1 influences FTi. We will address whether the role of AtGRP7 at the intersection between clock control, FTi and pathogen defense in Arabidopsis is conserved for HvGR-RBP1. Overall, the project contributes to the development of a functional cross-species network of FTi regulators, the major strategic aim of SPP1530.
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