Rice phenolics efflux transporter 2 (PEZ2) plays an important role in solubilizing apoplasmic iron

Abstract

Iron (Fe) is an essential micronutrient for plants; however, despite its abundance in soils it is not readily available in neutral to alkaline soils. Plants secrete phenolics, such as protocatechuic acid (PCA) and caffeic acid (CA), to absorb and utilize precipitated apoplasmic Fe from root surfaces. However, the synthesis and secretion of phenolics have not been well characterized in plants. We have identified and characterized a rice (Oryza sativa L.) mutant with reduced amounts of PCA and CA in xylem sap and root exudates; hence we named it phenolics efflux zero 2 (pez2). PEZ2 localized to the plasma membrane in onion (Allium cepa L.) epidermal cells and transported PCA when expressed in Xenopus laevis oocytes. PEZ2 expression was observed in whole root near root tips. Similarly, strong expression was observed in leaves. In line with reduced amounts of PCA and CA in xylem sap, the xylem Fe concentration was also low in pez2 plants. These results suggest that PEZ2 is involved in solubilization of apoplasmic Fe in rice.

The Phytosiderophore Efflux Transporter TOM2 Is Involved in Metal Transport in Rice

“…These results suggest that metal translocation was aberrant in TOM2 RNAi plants. Previously, phenolics efflux zero 1 and 2 (PEZ1 and PEZ2), the efflux transporters of protocatechuic acid, have been reported to contribute to the long-distance transport of iron through the solubilization of precipitated apoplasmic iron in the root xylem (58,59), suggesting that some transporters are necessary to mobilize metals accumulated in the apoplasm to transport them to sinks in plants.…”

Putrescine Alleviates Iron Deficiency via NO-Dependent Reutilization of Root Cell-Wall Fe in Arabidopsis

“…However, under certain conditions Fe is not readily available, and Fe is difficult to mobilize; thus, Fe stored in the plant needs to be reutilized. For example, phenolics are secreted to remobilize the root apoplastic Fe and improve Fe nutrition in red clover (Trifolium pratense) and rice (Oryza sativa) (Jin et al, 2007;Bashir et al, 2011). Moreover, Lei et al (2014) reported that the cell wall can be an important Fe source during periods of limited Fe supply.…”

Iron deficiency regulated OsOPT7 is essential for iron homeostasis in rice

“…For GSH uptake experiments oocytes of Xenopus laevis frogs were injected with either capped complementary RNA encoding OsOPT7 or water and incubated at 17 °C for 48 h (Kato et al 2001). Then oocytes were placed in Barth-MES; pH 5, 6 or 7) containing 100 µM GSH, (20 nM 3 H-labeled GSH) After 10 h incubation, oocytes were washed with 100 µl Barth-MES solution, followed by the addition of 100 µl of 10 % SDS, vortexed briefly and radioactivity of the oocytes was measured in a liquid scintillation analyzer as described previously Bashir et al 2011b). For NA and DMA transport experiments, OsOPT7 was cloned into pGEM-3zf(+) vector and substrate transport activity for NA and DMA was measured in oocytes at −80 and −100 mV, as described previously (Koike et al 2004).…”

“…The genes involved in MA biosynthesis have been characterized, and most of these genes are regulated by the Fe status of plants Lingam et al 2011;Kobayashi and Nishizawa 2012;Bashir et al 2010). After acquisition from soil, Fe is transported to leaves and developing seeds through a complex and complicated molecular mechanisms (Bashir et al 2013a;Ishimaru et al 2011b;Bashir et al 2011b;Yokosho et al 2009;Yamaji and Ma 2014). Moreover, cellular distribution of Fe is also very important and disturbance in cellular Fe homeostasis results in significant alteration in cellular metabolism (Bashir et al , c, 2013bKim et al 2006;Nozoye et al 2014a, b;Zhang et al 2012).…”