The Class III Peroxidase Encoding Gene AtPrx62 Positively and Spatiotemporally Regulates the Low pH-Induced Cell Death in Arabidopsis thaliana Roots.

Jonathas Pereira Graças,Philippe Ranocha,Christophe Dunand,Bruno Savelli,Victor Alexandre Vitorello,Elisabeth Jamet,Vincent Burlat

doi:10.3390/ijms21197191

Abstract

Exogenous low pH stress causes cell death in root cells, limiting root development, and agricultural production. Different lines of evidence suggested a relationship with cell wall (CW) remodeling players. We investigated whether class III peroxidase (CIII Prx) total activity, CIII Prx candidate gene expression, and reactive oxygen species (ROS) could modify CW structure during low pH-induced cell death in Arabidopsis thaliana roots. Wild-type roots displayed a good spatio-temporal correlation between the low pH-induced cell death and total CIII Prx activity in the early elongation (EZs), transition (TZs), and meristematic (MZs) zones. In situ mRNA hybridization showed that AtPrx62 transcripts accumulated only in roots treated at pH 4.6 in the same zones where cell death was induced. Furthermore, roots of the atprx62-1 knockout mutant showed decreased cell mortality under low pH compared to wild-type roots. Among the ROS, there was a drastic decrease in O2●− levels in the MZs of wild-type and atprx62-1 roots upon low pH stress. Together, our data demonstrate that AtPrx62 expression is induced by low pH and that the produced protein could positively regulate cell death. Whether the decrease in O2●− level is related to cell death induced upon low pH treatment remains to be elucidated.

Highlights

Around 70% of arable soils are acidic [1]
We examined in wild-type roots (Col-0) exposed to low pH whether a spatial correlation occurred between (i) cell death, (ii) CIII Prx activity, and (iii) reactive oxygen species (ROS) (O2− and H2O2) distribution (stained with nitro blue tetrazolium chloride (NBT) and hydroxyphenyl fluorescein (HPF), respectively)
In control roots treated at pH 5.8 for 2 or 3 h, cell death did not occur (Figure 1A,I) and CIII Prx activity was detected along the entire root except in meristematic zone (MZ) (Figure 1C,K; Supplementary Materials Figure S1B)

Summary

Introduction

Around 70% of arable soils are acidic (pH < 5.5) [1] In these soils, a combination of unfavorable factors occurs for plant development, such as mineral toxicity and low nutrient level, especially for cations such as calcium [2]. A combination of unfavorable factors occurs for plant development, such as mineral toxicity and low nutrient level, especially for cations such as calcium [2] These factors contribute to decreased root growth with a worldwide negative impact on crop productivity [3]. The level of expression of genes encoding several CW-related enzymes, including class III peroxidases (CIII Prxs) is increased in EZ [12] After reaching their full size, the epidermis trichoblast cells start to differentiate and form root hairs which elongate through tip growth [10]

Methods

Results

Conclusion