Leaf-Wounding Long-Distance Signaling Targets AtCuAOβ Leading to Root Phenotypic Plasticity.

Ilaria Fraudentali,Alessandra Cona,Riccardo Angelini,Paraskevi Tavladoraki,Renato A Rodrigues-Pousada

doi:10.3390/plants9020249

Ilaria Fraudentali, Alessandra Cona + Show 3 more

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https://doi.org/10.3390/plants9020249

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Abstract

The Arabidopsis gene AtCuAOβ (At4g14940) encodes an apoplastic copper amine oxidase (CuAO) highly expressed in guard cells of leaves and flowers and in root vascular tissues, especially in protoxylem and metaxylem precursors, where its expression is strongly induced by the wound signal methyl jasmonate (MeJA). The hydrogen peroxide (H2O2) derived by the AtCuAOβ-driven oxidation of the substrate putrescine (Put), mediates the MeJA–induced early root protoxylem differentiation. Considering that early root protoxylem maturation was also induced by both exogenous Put and leaf wounding through a signaling pathway involving H2O2, in the present study we investigated the role of AtCuAOβ in the leaf wounding-induced early protoxylem differentiation in combination with Put treatment. Quantitative and tissue specific analysis of AtCuAOβ gene expression by RT-qPCR and promoter::green fluorescent protein-β-glucuronidase fusion analysis revealed that wounding of the cotiledonary leaf induced AtCuAOβ gene expression which was particularly evident in root vascular tissues. AtCuAOβ loss-of-function mutants were unresponsive to the injury, not showing altered phenotype upon wounding in comparison to wild type seedlings. Exogenous Put and wounding did not show synergy in inducing early root protoxylem maturation, suggesting their involvement in a shared signaling pathway.

Highlights

Efficient plant resistance to environmental stresses relies on rapid stimulus perception and transmission within and among cells
Considering that AtCuAOβ expression is induced by the wound-signal hormone methyl jasmonate (MeJA), especially in the root vascular tissues [11], here, AtCuAOβ gene expression profile upon cotyledonary leaf wounding was investigated by AtCuAOβ-promoter::GFP-GUS transgenic analysis and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) (Figure 1)
The tissue-specific pattern revealed after wounding was similar to that observed in unwounded seedlings after prolonged staining (24 h) (Figure 1c,f), showing a similar pattern to that previously revealed in 4-day-old plants [11]

Summary

Introduction

Efficient plant resistance to environmental stresses relies on rapid stimulus perception and transmission within and among cells. Bidirectional extensive root-shoot communication allows plants to respond as whole organisms, coordinating and integrating reversible rapid physiological responses to phenotypic plasticity expression in different tissues. Wounding-induced long-distance signaling ensures defense responses throughout the plant body, preparing distal tissues for arriving chewing herbivores. The rapid systemic accumulation of the wound/herbivore signal jasmonic acid (JA) is triggered by leaf-to-leaf [3,4,5]. The wound-induced burst of JA occurs at a much lower extent than in leaf [7,8], possibly due to the lower level of α-linoleic acid in root plastid membranes [9], and JA accumulation mainly depends on locally [1] or systemically-induced [6] JA biosynthesis in shoots.

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