Allantoin accumulation mediated by allantoinase down-regulation and transport by Ureide Permease 5 (UPS5) confers salt stress tolerance to Arabidopsis plants.

IGNACIO LESCANO; CAROLINA MARTINI; TOMÁS TESSI; CLAUDIO GONZÁLEZ; MARCELO DESIMONE

Foz do Iguaçu

Congreso; 11th International Congress of Plant Molecular Biology.; 2015

Tropical legumes use the ureides allantoin and allantoate as major nodule-to-shoot nitrogen transport compounds. Since the complete enzyme set for ureide synthesis and several ureide permeases are widely distributed in the plant kingdom, it has been suggested that they participate in physiological processes not properly characterized yet. Recent studies associated allantoin with plant response to water stress in Arabidopsis thaliana. We observed that salt stress enhances allantoin accumulation in Arabidopsis plants in a process mediated by downregulation of the allantoin degrading enzyme allantoinase (AtALN). To study the physiological relevance of downregulation of AtALN during salt stress, the phenotypes of two independent T-DNA insertion lines aln-1 and aln-2, and stress-inducible AtALN transgenic lines (RD29A::ALN/aln-1) were comparatively characterized. Aln-1 and aln-2 plants showed elevated concentrations of allantoin and a significantly higher growth than wt plants under salt stress. RD29A::ALN/aln-1 plants were not able to accumulate allantoin and were severely damaged by salt. In addition, we analyzed the role of the Ureide Permease AtUPS5 in allantoin transport in response to salt stress by using two independent T-DNA insertion lines ups5-1 and ups5-2. The allantoin content in shoots was significantly lower in ups5 than in wt plants, while the allantoin content in roots was -2-fold higher in ups5 than in wt plants. Ups5 seedlings showed a reduced growth respect to wt plants under salt stress. This suggests that allantoin transport mediated by AtUPS5 is a necessary event in salt stress alleviation.