3 years ago

Type B response regulators act as central integrators in transcriptional control of the auxin biosynthesis enzyme TAA1.

Tao, Zhao, Li, Wang, Liu, Yan, Yang, Ljung
During embryogenesis and organ formation, establishing proper gradient is critical for auxin function, which is achieved through coordinated regulation of both auxin metabolism and transport. Expression of auxin biosynthetic genes is often tissue specific and is regulated by environmental signals. However, the underlying regulatory mechanisms remain elusive. Here, we investigated the transcriptional regulation of a key auxin biosynthetic gene, TAA1 (L-Tryptophan aminotransferase of Arabidopsis 1). A canonical and a novel ARR (Arabidopsis response regulators) binding site were identified in the promoter and the second intron of TAA1, which were required for its tissue specific expression. C-terminals of a subset of the type B ARRs selectively bind to one or both cis-elements and activate the expression of TAA1. We further demonstrated that the ARRs not only mediate the transcriptional regulation of TAA1 by cytokinins, but also mediate its regulation by ethylene, light and developmental signals. Through direct protein-protein interactions, the transcriptional activity of ARR1 is enhanced by ARR12, DELLAs and EIN3. Our study thus revealed the ARR proteins act as key node that mediate the regulation of auxin biosynthesis by various hormonal, environmental and developmental signals through transcriptional regulation of the key auxin biosynthesis geneTAA1.

Publisher URL: http://doi.org/10.1104/pp.17.00878

DOI: 10.1104/pp.17.00878

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