CZ.1.07/2.3.00/ Employment of Newly Graduated Doctors of Science for Scientific Excellence 2 nd Postdoc Presentation Day Name of the postdoc: Markéta Žďárská

Project title: The role of cytokinin-ethylene signaling crosstalk in plant development Mentor: doc. RNDr. Jan Hejátko, Ph.D. Faculty/Department/Research group: CEITEC-MU, Research group Functional Genomics and Proteomics of Plants Start date of postdoc (in the project): May 1st,

Introduction Cytokinin-ethylene crosstalk knowledge (Zdarska et al, 2013) 3  First connections: exogenous CK application inhibited the elongation and formation of lateral roots in etiolated seedlings (Bertell and Eliasson, 1992).  CK stimulates ethylene production (Cary et al., 1995).  CK stabilizes proteins of ACC synthase: ACS5 and ACS9 (Kakimoto et al, 1998; Hansen et al, 2009).  CK mediates ethylene biosynthesis in roots (Zdarska et al, 2013).

Research aims  Analysis of molecular mechanisms involved in the CK- mediated regulation of ethylene biosynthesis  Inspection of the potential crosstalk between CK- and ethylene-mediated MSP  Identification of the molecular nature of conditional switch leading to changes between CK and ethylene signaling

Cytokinin and ethylene signaling pathways ETR 1 (Schaller et al, 2012) ETR1 reveals both STK and HK activity and embody high levels of similarity to HK acting in the MSP (Schaller et al, 2011). ETR1 interacts with AHP1, AHP3 and ARR4 (Urao et al, 2000). ETR1 interacts with AHP1-3 and AHP5-6 (Hrdinová, unpublished) Ethylene receptors (STK activity) (Etheridge et al., 2006)

Cross-talk at signaling pathways ACC application regulates ARRs-A differentially in Col-0: upregulation of ARR3, 5, 6 and 15 in shoots downregulation of ARR5, 6, 8 and 15 in roots ACC treatment does not activate MSP in ahk2 ahk3 6 EXPRESSION ANALYSIS OF ARR-A (qRT-PCR) (D‘ Agostino, 2000) Cytokinin response regulators ARR-A

Cross-talk at signaling pathways ahk2 ahk4 - upregulation of several ARRs-A in shoots and almost no effect in roots 7 ahk3 ahk4 – dowregulation of ARRs-A in shoots and generally no effect in roots 1. Overall, these data suggest that AHK2 and AHK3 receptors modulate ethylene dependent activation of MSP output - AHK2 in roots and AHK3 in both tissues.

 almost all ARRs-A are induced by BAP (aromatic CK) treatment in shoots and roots of Col-0 and etr1-1 (unable to bind ethylene - constitutively active)  enhanced inducibity of ARR3, 5 and 16 in roots of etr1-1 than in Col-0 (denoted by red triangles above bars) 8 2. ETR1 interferes with CK in the regulation of MSP activity

CK and ethylene crosstalk model suggestion in the root CK treatment upregulates several proteins involved in the ethylene biosynthesis, resulting in prompt ethylene upregulation as an effect of root-specific ACC accumulation (Zdarska et al., 2013). AHK2 and AHK3 receptors modulate ethylene dependent activation of MSP output. Ethylene binds to ETR1 that interacts via ETR1 RD with AHP proteins (AHP1-3,5) and modulates MSP output at the level of expression ARRs-A. Ethylene signaling plays a role in the CK- dependent regulation of RAM size. 9 Overall, these data show the integration of both CK and ethylene signaling and its display as a mutual CK-ethylene response.

Future prospects  Publication: The role of cytokinin-ethylene signaling crosstalk in plant development  e.g. Plant Physiology or Plant Journal (2014)  Internship at Caltech, CA – laboratory of prof. Meyerowitz  September 2014 – February 2015  publication e.g. Plant Physiology or Plant Cell (2015) 10 Thank you for attention!