Ureide Permease 5 (AtUPS5) Connects Cell Compartments Involved in Ureide Metabolism

LESCANO, IGNACIO; BOGINO, MARÍA FLORENCIA; MARTINI, CAROLINA; TESSI, TOMÁS MARÍA; GONZÁLEZ, CLAUDIO ALEJANDRO; SCHUMACHER, KARIN; DESIMONE, MARCELO

PLANT PHYSIOLOGY.

AMER SOC PLANT BIOLOGISTS

Año: 2020 vol. 182 p. 1310 - 1325

0032-0889

Allantoin is a purine oxidative product involved in long distance transport of organic nitrogen in nodulating legumes and wasrecently shown to play a role in stress tolerance in other plants. The subcellular localization of enzymes that catalyze allantoinsynthesis and degradation indicates that allantoin is produced in peroxisomes and degraded in the endoplasmic reticulum (ER).Although it has been determined that allantoin is mostly synthesized in roots and transported to shoots either for organicnitrogen translocation in legumes or for plant protection during stress in Arabidopsis (Arabidopsis thaliana), the mechanism andmolecular components of allantoin export from root cells are still unknown. AtUPS5 (Arabidopsis UREIDE PERMEASE 5) is atransmembrane protein that transports allantoin with high affinity when expressed in yeast. The subcellular fate of splicingvariants AtUPS5L (long) and AtUPS5S (short) was studied by tagging them with fluorescent proteins in their cytosolic loops.The capability of these fusion proteins to complement the function of the native proteins was demonstrated by nutritional andsalt stress experiments. Both variants localized to the ER, but the AtUPS5L variant was also detected in the trans-Golgi network/early endosome and at the plasma membrane. AtUPS5L and AtUPS5S localization indicates that they could have different rolesin allantoin distribution between subcellular compartments. Our data suggest that under nonstress conditions UPS5L and UPS5Smay function in allantoin degradation for nutrient recycling, whereas under stress, both genes may be involved in vesicularexport allowing allantoin translocation from roots to shoots.