Induction of auxin biosynthesis and WOX5 repression mediate changes in root development in Arabidopsis exposed to chitosan

Federico Lopez-Moya,David Esteve-Bruna,Ernesto A Zavala-Gonzalez,David Alabadí,Luis V Lopez-Llorca,Miguel A Blázquez,Nuria Escudero

doi:10.1038/s41598-017-16874-5

Abstract

Chitosan is a natural polymer with applications in agriculture, which causes plasma membrane permeabilisation and induction of intracellular reactive oxygen species (ROS) in plants. Chitosan has been mostly applied in the phylloplane to control plant diseases and to enhance plant defences, but has also been considered for controlling root pests. However, the effect of chitosan on roots is virtually unknown. In this work, we show that chitosan interfered with auxin homeostasis in Arabidopsis roots, promoting a 2–3 fold accumulation of indole acetic acid (IAA). We observed chitosan dose-dependent alterations of auxin synthesis, transport and signalling in Arabidopsis roots. As a consequence, high doses of chitosan reduce WOX5 expression in the root apical meristem and arrest root growth. Chitosan also propitiates accumulation of salicylic (SA) and jasmonic (JA) acids in Arabidopsis roots by induction of genes involved in their biosynthesis and signalling. In addition, high-dose chitosan irrigation of tomato and barley plants also arrests root development. Tomato root apices treated with chitosan showed isodiametric cells respect to rectangular cells in the controls. We found that chitosan causes strong alterations in root cell morphology. Our results highlight the importance of considering chitosan dose during agronomical applications to the rhizosphere.

Highlights

Soil-borne pathogens cause some of the most serious diseases of cultivated crops and pose a serious threat to global food security[1]
To investigate the possible effects on root growth of chitosan applied to the rhizosphere, we examined the phenotype of Arabidopsis plants (Col-0) treated with increasing doses of chitosan (Fig. 1A and B)
Arabidopsis roots exposed to 1 mg ml−1 chitosan solution for 2 h showed an accumulation of reactive oxygen species (ROS) (Fig. S1)

Summary

Introduction

Soil-borne pathogens cause some of the most serious diseases of cultivated crops and pose a serious threat to global food security[1]. Infections caused by soil borne organisms such as nematodes, fungi or bacteria can result in crop losses of more than $120 billion dollars per year in the USA only[2] These losses together with the restriction in the use of fungicides, bactericides and nematicides justify the need to study and develop more sustainable methods of control. Baque et al.[27] found that chitosan applied to adventitious root cultures enhances secondary metabolite production and decreases root growth on Morindia plants. Still the direct effect of chitosan on plant root at physiological and cellular levels is not known. In this study we investigate the effect of chitosan on root development trying to establish the basis for its application in agriculture. We have determined the effect of chitosan on plant growth and apical root meristem cell dynamics. This work provides a better understanding of the mode of action of chitosan on root development, focusing on hormone homeostasis

Methods

Results

Conclusion