The Apoplastic Copper AMINE OXIDASE1 Mediates Jasmonic Acid-Induced Protoxylem Differentiation in Arabidopsis Roots

The MeJA-inducible copper amine oxidase AtAO1 is expressed in xylem tissue and guard cells

“…We have recently demonstrated, by pharmacological and forward/reverse genetic approaches, that AtAO1-driven H 2 O 2 production has a key role in the early protoxylem differentiation occurring in the primary root apex upon treatment with the wound-signal MeJA. 8 In this regard, it has been shown that in roots of MeJA-treated seedlings, fully differentiated protoxylem vessels, in addition to display higher AtAO1 expression levels, appear closer to the root apex with respect to roots from control plants. Conversely, Atao1 loss-of-function mutants have been shown to be unresponsive to the MeJA-induced early protoxylem differentiation.…”

“…[3][4][5] Cellwall resident AOs show high levels of expression in root vascular tissues of different plant species, especially in developing xylem tissues. [7][8][9][10] In this regard, it has been suggested that PA-derived H 2 O 2 may play a role in maturation of xylem cells by triggering the peroxidase-driven polymerisation of lignin and by signaling developmental programmed cell death (PCD) in differentiating xylem precursors. Growing evidence allows us to hypothesize that apoplastic PA-derived H 2 O 2 has a role in inducing xylem differentiation under stress conditions, while its involvement under physiological conditions needs to be further explored.…”

“…Growing evidence allows us to hypothesize that apoplastic PA-derived H 2 O 2 has a role in inducing xylem differentiation under stress conditions, while its involvement under physiological conditions needs to be further explored. 8,[10][11][12] The Arabidopsis thaliana At4g14940 gene (AtAO1) encodes for an apoplastic MeJAinducible CuAO that has been revealed to be expressed in root protoxylem and metaxylem precursors. We have recently demonstrated, by pharmacological and forward/reverse genetic approaches, that AtAO1-driven H 2 O 2 production has a key role in the early protoxylem differentiation occurring in the primary root apex upon treatment with the wound-signal MeJA.…”

“…The involvement of AtAO1 in this event is further supported by the reduction of the levels of the AtAO1 substrate putrescine in roots of MeJA-treated wild type (WT) plants. 8 A key role in MeJAinduced early differentiation of root protoxylem has been ascribed to the AtAO1-produced H 2 O 2 considering that the effect observed in roots of MeJA-treated WT plants is reversible upon H 2 O 2 removal and that an accumulation of H 2 O 2 at the site of appearance of protoxylem cells with fully developed secondary walls has been revealed in the same roots. 8 Early protoxylem differentiation was also induced in AtAO1 overexpressing plants and in WT plants upon treatment with putrescine.…”

Role of Reactive Oxygen Species during Cell Expansion in Leaves

“…Both amine and oxalate oxidases have a major impact on apoplastic H 2 O 2 production (Kärkönen and Kuchitsu, 2015). Two types of amine oxidases, copper-containing oxidases and polyamine oxidases, catalyze the oxidative deamination of di-and polyamines, resulting in the formation of H 2 O 2 (Ghuge et al, 2015). To what extent these enzymes contribute to growth regulation during development still needs to be further explored.…”