Jasmonic Acid Methyl Ester Induces Xylogenesis and Modulates Auxin-Induced Xylary Cell Identity with NO Involvement

Abstract

In Arabidopsis basal hypocotyls of dark-grown seedlings, xylary cells may form from the pericycle as an alternative to adventitious roots. Several hormones may induce xylogenesis, as Jasmonic acid (JA), as well as indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) auxins, which also affect xylary identity. Studies with the ethylene (ET)-perception mutant ein3eil1 and the ET-precursor 1-aminocyclopropane-1-carboxylic acid (ACC), also demonstrate ET involvement in IBA-induced ectopic metaxylem. Moreover, nitric oxide (NO), produced after IBA/IAA-treatments, may affect JA signalling and interact positively/negatively with ET. To date, NO-involvement in ET/JA-mediated xylogenesis has never been investigated. To study this, and unravel JA-effects on xylary identity, xylogenesis was investigated in hypocotyls of seedlings treated with JA methyl-ester (JAMe) with/without ACC, IBA, IAA. Wild-type (wt) and ein3eil1 responses to hormonal treatments were compared, and the NO signal was quantified and its role evaluated by using NO-donors/scavengers. Ectopic-protoxylem increased in the wt only after treatment with JAMe(10 μM), whereas in ein3eil1 with any JAMe concentration. NO was detected in cells leading to either xylogenesis or adventitious rooting, and increased after treatment with JAMe(10 μM) combined or not with IBA(10 μM). Xylary identity changed when JAMe was applied with each auxin. Altogether, the results show that xylogenesis is induced by JA and NO positively regulates this process. In addition, NO also negatively interacts with ET-signalling and modulates auxin-induced xylary identity.

Peroxisomal PEX7 Receptor Affects Cadmium-Induced ROS and Auxin Homeostasis in Arabidopsis Root System

“…Thus, it is possible that also IBA contributes to improve the plant defense to the pollutant toxicity, with its levels remaining as high as those of IAA, because it is not being used for the LRs. The high levels of the two endogenous auxins might result in their reduced use for the biosynthesis of stress- and auxin-related hormones, such as ethylene and jasmonates, whose roles as root inducers have been demonstrated [ 22 , 24 , 83 ]. In accordance with this, increased levels of the two auxins have been detected in different plant species after the exposure to different stresses, such as drought [ 84 ], osmotic [ 85 ], or toxic metals [ 86 ].…”

“…In plant, the auxin pool comprises free IAA, IAA conjugates, and the IAA-precursor IBA [ 19 ]. In Arabidopsis thaliana , IBA activity completely depends on its conversion into IAA in the target cells [ 20 , 21 ]; however its formation occurs by a modulated conversion into IAA involving nitric oxide (NO) production, as demonstrated for AR formation [ 22 , 23 , 24 ].…”

Jasmonates, Ethylene and Brassinosteroids Control Adventitious and Lateral Rooting as Stress Avoidance Responses to Heavy Metals and Metalloids

“…In the pericycle cells of Arabidopsis basal hypocotyl, NO is detected at the early stages of both AR formation and xylogenesis, and its production is enhanced by MeJA [ 154 ]. Interestingly, the IBA/IAA-induced adventitious rooting is increased by MeJA to a similar extent as xylogenesis, suggesting a role for JA in modulating adventitious rooting and xylogenesis programs in the same target cells through an interaction with NO, whose signal is enhanced early by MeJA [ 154 ].…”

“…In the pericycle cells of Arabidopsis basal hypocotyl, NO is detected at the early stages of both AR formation and xylogenesis, and its production is enhanced by MeJA [ 154 ]. Interestingly, the IBA/IAA-induced adventitious rooting is increased by MeJA to a similar extent as xylogenesis, suggesting a role for JA in modulating adventitious rooting and xylogenesis programs in the same target cells through an interaction with NO, whose signal is enhanced early by MeJA [ 154 ]. Since ARs are induced in the Arabidopsis hypocotyl by auxin (through the induction of anticlinal ACDs) in competition with xylogenesis (occurring via periclinal ACDs) [ 32 ], it is possible that a NO-guided rearrangement of the cytoskeleton and of cell plate orientation occurs, thereby changing the developmental program.…”

“…Interestingly, the AR primordia of Arabidopsis do not need prolonged NO activity, perhaps because they are capable of sustaining their growth after the QC is established, which occurs at stage VII of development [ 10 ], i.e., exactly when the NO signal is quenched [ 154 ]. In accordance, it has been suggested that when NO production is auxin-dependent it may occur exclusively under specific temporal and spatial contexts [ 152 ].…”