Mechanism of kinetin-induced death of Vicia faba ssp. minor root cortex cells

Abstract

Cell death (CD) may be induced by endogenous or exogenous factors and contributes to all the steps of plant development. This paper presents results related to the mechanism of CD regulation induced by kinetin (Kin) in the root cortex of Vicia faba ssp. minor. To explain the process, 6-(2-hydroxy-3-methylbenzylamino)purine (PI-55), adenine (Ad), 5′-amine-5′-deoxyadenosine (Ado) and N-(2-chloro-4-piridylo)-N′-phenylurea (CPPU) were applied to (i) block cytokinin receptors (CKs) and inhibit the activities of enzymes of CK metabolism, i.e., (ii) phosphoribosyltransferase, (iii) kinases, and (iv) oxidases, respectively. Moreover, ethylene glycol-bis(β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid (EGTA), lanthanum chloride (LaCl3), ruthenium red (RRed) and cyclosporine A (CS-A) were applied to (i) chelate extracellular calcium ions (Ca2+) as well as blocks of (ii) plasma-, (iii) endoplasmic reticulum- (ER) membrane Ca2+ ion channels and (iv) mitochondria- (MIT) Ca2+ ions release by permeability transition por (PTP), respectively. The measured physiological effectiveness of these factors was the number of living and dying cortex cells estimated with orange acridine (OA) and ethidium bromide (EB), the amounts of cytosolic Ca2+ ions with chlortetracycline (CTC) staining and the intensity of chromatin and Ca2+-CTC complex fluorescence, respectively. Moreover, the role of sorafenib, an inhibitor of RAF kinase, on the vitality of cortex cells and ethylene levels as well as the activities of RAF-like kinase and MEK2 with Syntide-2 and Mek2 as substrates were studied. The results clarified the previously presented suggestion that Kin is converted to appropriate ribotides (5′-monophosphate ribonucleotides), which cooperate with the ethylene and Ca2+ ion signalling pathways to transduce the signal of kinetin-programmed cell death (Kin-PCD). Based on the present and previously published results related to Kin-PCD, the crosstalk between ethylene and MAP kinase signalling, as well as inhibitors of CK receptors and enzymes of their metabolism, is proposed.

Kinetin induces microtubular breakdown, cell cycle arrest and programmed cell death in tobacco BY-2 cells

“…A study on kinetin-induced cell death in the V. faba ssp. minor system (Kaźmierczak et al 2021 ) showed an increase of cytosolic calcium, which was accentuated by Ruthenium Red, suggesting that this calcium originates from internal stores, which is consistent with the current study. However, in the V. faba system, the elevated cytosolic calcium in presence of Ruthenium Red was accompanied by reduced cell death, which was also seen in the lace plant (Fraser et al 2020 ).…”

“…Based on the ligand affinity patterns of different cytokinins, this receptor was also suggested to be involved in kinetin-induced cell death in V. faba ssp. minor roots (Kaźmierczak et al 2021 ). Generally, cytokinin receptors deploy signalling through mobile response regulators, and some of those connect with G-protein signalling (Wang et al 2017 ), which also would explain findings, where overexpression of a trimeric G-protein leads to a higher sensitivity against cytokinins (Plakidou-Dymock et al 1998 ).…”

“…A study on kinetin-induced cell death in the V. faba ssp. minor system (Kaźmierczak et al 2021) showed an increase of cytosolic Fig. 10 Effect of kinetin on actin filaments visualised by the marker FABD2-GFP and followed by spinning-disc confocal microscopy through days 3 until 7.…”

“…However, cortical actin, subtending the plasma membrane, is rapidly depleted during HR (Chang et al 2015 ), whilst the developmental PCD during vascular differentiation goes along with a specific bundling and elimination of cortical microtubules (Iakimova and Woltering 2017 ). Aerenchymatic cells as well as vascular bundles differentiate from parenchymatic precursors and undergo terminal differentiation in response to specific plant hormones, such as auxin and kinetin (Byczkowska et al 2013 ), involving ROS and ethylene as well (Evans 2003 ; Kaźmierczak et al 2021 ).…”

Hormonal Signaling during dPCD: Cytokinin as the Determinant of RNase-Based Self-Incompatibility in Solanaceae

“…An analysis of distinctive features (DNA fragmentation, the condensation of nuclear chromatin, and the release of cytochrome c from mitochondria) revealed a programmed character of induced cell death [60]. Kaźmierczak et al [63] describe the mechanism of kinetin-induced death of Vicia faba ssp. minor root cortex cells.…”