Abstract
Plant defence responses to adverse environmental conditions include different stress signalling, allowing plant acclimation and survival. Among these responses one of the most common, immediate, and effective is the modulation of the stomatal aperture, which integrates different transduction pathways involving hydrogen peroxide (H2O2), calcium (Ca2+), nitric oxide (NO), phytohormones and other signalling components. The Arabidopsis thaliana copper amine oxidases β (AtCuAOβ) encodes an apoplastic CuAO expressed in guard cells and root protoxylem tissues which oxidizes polyamines to aminoaldehydes with the production of H2O2 and ammonia. Here, its role in stomatal closure, signalled by the wound-associated phytohormone methyl-jasmonate (MeJA) was explored by pharmacological and genetic approaches. Obtained data show that AtCuAOβ tissue-specific expression is induced by MeJA, especially in stomata guard cells. Interestingly, two Atcuaoβ T-DNA insertional mutants are unresponsive to this hormone, showing a compromised MeJA-mediated stomatal closure compared to the wild-type (WT) plants. Coherently, Atcuaoβ mutants also show compromised H2O2-production in guard cells upon MeJA treatment. Furthermore, the H2O2 scavenger N,N1-dimethylthiourea (DMTU) and the CuAO-specific inhibitor 2-bromoethylamine (2-BrEtA) both reversed the MeJA-induced stomatal closure and the H2O2 production in WT plants. Our data suggest that AtCuAOβ is involved in the H2O2 production implicated in MeJA-induced stomatal closure.
Highlights
Growing anthropogenic pressure, ongoing climate changes and the intensification of extreme events expose plant organisms to unusual and unpredictable environmental conditions, subjecting them to intense abiotic stresses, greatly varying in intensity, frequency and duration
AtCuAOβ encodes an apoplastic CuAO expressed at the early stages of vascular tissue differentiation in root, as well as in stomata guard cells [8,9]
To integrate information from previous reported data, AtCuAOβ expression pattern has been analysed in seedlings and in leaves, flowers and siliques of AtCuAOβ-promoter::GFPGUS Arabidopsis adult transgenic plants
Summary
Growing anthropogenic pressure, ongoing climate changes and the intensification of extreme events expose plant organisms to unusual and unpredictable environmental conditions, subjecting them to intense abiotic stresses, greatly varying in intensity, frequency and duration. In the current context of dramatic environmental changes, such as the increase in atmospheric CO2 , which is strongly responsible for the rise in temperature and the decrease in water resources, the understanding of the modulation of stomata responses is of great importance in the design of sustainable agriculture, which requires new varieties with improved growth-water loss trade-off. Stomatal movement is a complex physiological event evolved to regulate gas exchanges and thermoregulation, finely modulated by different exogenous factors, such as light, temperature, drought, and pathogens. In this context, mechanical stresses caused by atmospheric agents or biotic factors, such as herbivorous animals, leaf-chewing or sucking insects and root nematodes, lead to tissue damage, requiring an immediate array of molecular responses to limit the injury damage and/or leading to increased defence capacity towards pests
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