Caged Phytohormones: From Chemical Inactivation to Controlled Physiological Response

Abstract

Plant hormones, also called phytohormones, are small signaling molecules regulating a wide range of growth and developmental processes. These unique compounds respond to both external (light, temperature, water, nutrition, or pathogen attack) and internal factors (e.g., age) and mediate signal transduction leading to gene expression with the aim of allowing plants to adapt to constantly changing environmental conditions. Within the regulation of biological processes, individual groups of phytohormones act mostly through a web of interconnected responses rather than linear pathways, making elucidation of their mode of action in living organisms quite challenging. To further progress with our knowledge, the development of novel tools for phytohormone research is required. Although plenty of small molecules targeting phytohormone metabolic or signaling pathways (agonists, antagonists, and inhibitors) and labeled or tagged (fluorescently, isotopically, or biotinylated) compounds have been produced, the control over them in vivo is lost at the time of their administration. Caged compounds, on the other hand, represent a new approach to the development of small organic substances for phytohormone research. The term “caged compounds” refers to light-sensitive probes with latent biological activity, where the active molecule can be freed using a light beam in a highly spatio/temporal-, amplitude-, or frequency-defined manner. This review summarizes the up-to-date development in the field of caged plant hormones. Research progress is arranged in chronological order for each phytohormone regardless of the cage compound formulation and bacterial/plant/animal cell applications. Several known drawbacks and possible directions for future research are highlighted.

BdGUCD1 and Cyclic GMP Are Required for Responses of Brachypodium distachyon to Fusarium pseudograminearum in the Mechanism Involving Jasmonate

“…Moreover, there is still much missing information and gaps in the understanding of the interactions between cGMP and hormones in response to pathogen infection. There is evidence that cGMP, GCs [ 4 , 5 , 14 ], and hormones are involved in the plant response to pathogen infection [ 15 , 16 , 17 , 18 ]. Therefore, it is worth exploring whether and how these molecules cooperate.…”

o-Nitrobenzyl-Based Caged exo-16,17-Dihydro-gibberellin A5-13-acetate for Photocontrolled Release of Plant Growth Regulators

“…Silica gel was used for flash column chromatography. The 1 H and 13 C spectra were recorded in CDCl 3 using Bruker spectrometers at 500 and 125 MHz, respectively. The UV/vis absorption spectra were recorded on a Persee UV−vis spectrophotometer.…”

“…Although various articles and reviews related to caged PGRs have been reported, 15,16,36−39 most of them focused on the strategy of using PRPGs as "switches" to trigger biological activity release. In this report, to potentiate bioefficacy and costeffectiveness, a series of caged DHGA 5 derivatives were designed 13 Caged compounds are metabolically inert after being applied to the biological system, while light exposure leads to the release of active molecules that trigger the expected physiological response. based on o-nitrobenzyl (oNB), and phototriggered active DHGA 5 release could be achieved through ester bond cleavage.…”

“…Photoactivation processes offer the advantage of high spatiotemporal resolution due to light specific intensity and wavelength (Figure B) . Consequently, the utilization of PRPGs to control the release of bioactive compounds, including plant growth regulators (PGRs), has become a subject of increasing interest in various applications. − …”

“…(A) Photocaged compounds including nucleotides, small molecules, sugar signals, and PGRs in previous reports. ,,− (B) Principles of photocontrolled release of caged compounds and compounds reported in previous work . Caged compounds are metabolically inert after being applied to the biological system, while light exposure leads to the release of active molecules that trigger the expected physiological response.…”