iP & OEIP – Cytokinin Micro Application Modulates Root Development with High Spatial Resolution

Abstract

which potentially allows electronic control of their local concentrations by precise hormone delivery. Organic electronic ion pumps (OEIPs) are a novel technology that enables the highly controlled transport of various organic substances with unprecedented spatial and temporal resolution. [1] Ions are transported from a pump reservoir to a target matrix through a delivery channel carrying ion (cation/anion) exchange membranes (IEMs) with a high density of fixed charged groups. Flow-free and highly selective transport of the ions is achieved by the application of a controlled electric current, resulting in a steep concentration gradient at the delivery channel outlet. In addition, simple manipulation of the electrical parameters (voltage/current) can precisely fine-tune the amounts of molecules delivered to the target tissue. [1] The OEIP approach was primarily developed for biomedical applications for precise delivery of small neurosignaling inorganic ions, such as K + , Na + , Cl − , and Ca 2+ , [2] and smaller organic compounds, such as γ-aminobutyric acid (GABA), [3,4] glutamate (Glu) [3] and acetylcholine (ACh). [5][6][7] Further optimization of IEM materials has resulted in the development of hyperbranched membranes (dendrolytes) enabling the transport of larger aromatic substances, such as the plant hormones indole-3-acetic acid (IAA) [8] or abscisic acid (ABA). [9] State-of-the-art technology based on organic electronics can be used as a flow-free delivery method for organic substances with high spatial resolution. Such highly targeted drug micro applications can be used in plant research for the regulation of physiological processes on tissue and cellular levels. Here, for the first time, an organic electronic ion pump (OEIP) is reported that can transport an isoprenoid-type cytokinin, N 6 -isopentenyladenine (iP), to intact plants. Cytokinins (CKs) are plant hormones involved in many essential physiological processes, including primary root (PR) and lateral root (LR) development. Using the Arabidopsis thaliana root as a model system, efficient iP delivery is demonstrated with a biological output -cytokinin-related PR and LR growth inhibition. The spatial resolution of iP delivery, defined for the first time for an organic compound, is shown to be less than 1 mm, exclusively affecting the OEIP-targeted LR. Results from the application of the high-resolution OIEP treatment method confirm previously published findings showing that the influence of CKs may vary at different stages of LR development. Thus, OEIP-based technologies offer a novel, electronically controlled method for phytohormone delivery that could contribute to unraveling cytokinin functions during different developmental processes with high specificity.

Flexible Organic Electronic Ion Pump for Flow‐Free Phytohormone Delivery into Vasculature of Intact Plants

“…[ 10 ] The OEIP was initially developed by Berggren and co‐workers [ 11 ] and has been applied in numerous in vitro biomedical studies [ 12 , 13 , 14 ] and also in vivo interfacing with animal models for controlling neural activity. [ 15 , 16 ] Moreover, the OEIP has been applied to plants, for controlled delivery of the phytohormones auxin [ 17 ] and cytokinin [ 18 ] at the proximity of the root of Arabidopsis thaliana , demonstrating bioelectronic control of root growth. Typically, the OEIP consists of a polyelectrolyte channel that connects source and target electrolytes.…”

Synergism of vesicle trafficking and cytoskeleton during regulation of plant growth and development: A mechanistic outlook

“…The creation of plant shapes, uniqueness of meristems, and growth responses are regulated by the growth hormone auxin. This hormone is primarily synthesized in the shoot apex and subsequently transported towards the base, establishing a concentration gradient [ 72 ].…”