Ubogoeva, E. | Search bioRxiv

bioRxiv2024

Cytokinin-inducible DIRIGENT13 involved in lignan synthesis and ROS accumulation promotes root growth and abiotic stress tolerance in Arabidopsis

Dirigent (DIR) proteins mediate regio- and stereoselectivity of phenoxy radical coupling of monolignols for (neo)lignan or lignin synthesis. However, the role of DIR proteins and lignans in plant development and response to environmental stresses remains elusive. Here, we provide a functional characterization of the cytokinin-responsive DIRIGENT13 (DIR13) in Arabidopsis thaliana. DIR13 was localized to the root endodermis and at the margins of lateral root primordia and lateral roots. While not necessary for Casparian strip formation, DIR13 promoted both main and lateral root growth. Untargeted metabolomics and imaging mass spectrometry analyses unveiled the role of DIR13 in facilitating (neo)lignan synthesis in primary and lateral roots. Interestingly, DIR13 activated the production of putative oxomatairesinol and matairesinol-cysteine which are oxidative derivatives of the lignan matairesinol. Our data also identified DIR13 as an enhancer of salt and drought tolerance. Particularly, DIR13 attenuated salt stress-mediated inhibition of germination and root growth. Moreover, DIR13 activated reactive oxygen species (ROS) accumulation both under control and salt stress conditions, and cytokinin further enhanced the salt-induced ROS production specifically in the DIR13 overexpressing line. Our results uncover a role for DIR13-produced lignans in the priming of ROS accumulation, mediating both abiotic stress tolerance and the control of root architecture.

plant biology↗

bioRxiv2021

AHK5 mediates ETR1-initiated multistep phosphorelay in Arabidopsis

Plants, like other sessile organisms, need to sense many different signals, and in response to them, modify their developmental programs to be able to survive in a highly changing environment. The multistep phosphorelay (MSP) in plants is a good candidate for a response mechanism that integrates multiple signal types both environmental and intrinsic in origin. Recently, ethylene was shown to control MSP activity via the histidine kinase (HK) activity of ETHYLENE RESPONSE 1 (ETR1)1,2, but the underlying molecular mechanism still remains unclear. Here we show that although ETR1 is an active HK, its receiver domain (ETR1RD) is structurally and functionally unable to accept the phosphate from the phosphorylated His in the ETR1 HK domain (ETR1HK) to initiate the phosphorelay to ARABIDOPSIS HISTIDINE-CONTAINING PHOSPHOTRANSMITTERs (AHPs), the next link downstream members in MSP signaling. Instead, ETR1 interacts with another HK ARABIDOPSIS HISTIDINE KINASE 5 (AHK5) and transfers the phosphate from ETR1HK through the receiver domain of AHK5 (AHK5RD), and subsequently to AHP1, AHP2 and AHP3, independently of the HK activity of AHK5. We show that AHK5 is necessary for ethylene-initiated, but not cytokinin-initiated, MSP signaling in planta and that it thus mediates hormonal control of root growth.

plant biology↗