NRT1.1B improves selenium concentrations in rice grains by facilitating selenomethinone translocation

Abstract

Summary Selenium (Se) is an essential trace element for humans and other animals, yet approximately one billion people worldwide suffer from Se deficiency. Rice is a staple food for over half of the world's population that is a major dietary source of Se. In paddy soils, rice roots mainly take up selenite. Se speciation analysis indicated that most of the selenite absorbed by rice is predominantly transformed into selenomethinone (SeMet) and retained in roots. However, the mechanism by which SeMet is transported in plants remains largely unknown. In this study, SeMet uptake was found to be an energy‐dependent symport process involving H + transport, with neutral amino acids strongly inhibiting SeMet uptake. We further revealed that NRT1.1B, a member of rice peptide transporter (PTR) family which plays an important role in nitrate uptake and transport in rice, displays SeMet transport activity in yeast and Xenopus oocyte. The uptake rate of SeMet in the roots and its accumulation rate in the shoots of nrt1.1b mutant were significantly repressed. Conversely, the overexpression of NRT1.1B in rice significantly promoted SeMet translocation from roots to shoots, resulting in increased Se concentrations in shoots and rice grains. With vascular‐specific expression of NRT1.1B , the grain Se concentration was 1.83‐fold higher than that of wild type. These results strongly demonstrate that NRT1.1B holds great potential for the improvement of Se concentrations in grains by facilitating SeMet translocation, and the findings provide novel insight into breeding of Se‐enriched rice varieties.

Quick selenium accumulation in the selenium-rich rice and its physiological responses in changing selenium environments

“…In contrast with the control Se-free rice which maintained a relatively stable expression of CAL1, its expression in the Se-rich rice decreased gradually to the lowest level in 40 μM of Se, indicating that CAL1 may negatively mediate the sensitiveness of Se application in the Se-rich rice. In addition, NRT1.1B, a member of the rice peptide transporter (PTR) family, is thought to improve the accumulation of Se in grains by facilitating selenomethinone (SeMet) translocation, provide novel insights into the breeding of Se-rich rice varieties [10]. In line with the previous report that roots of Se-hyper accumulator plants activate the expressions of ion transporters [49], the intervention on the expression activities of the abovementioned factors may contribute to the uptake capacity of Se for rice varieties.…”

“…Plant scientists believe that Se is a beneficial element, since it is involved in regulating plant growth and development, ranging from regulating plant photosynthesis and respiration, reducing free radicals damages, enhancing plant stress resistance, to alleviating the heavy metals-induced toxicity [1,6]. At the same time, it can increase the contents of chlorophyll and carotenoid leaves, reducing damages caused by ultraviolet-induced oxidative stresses [8][9][10]. It has been demonstrated that Se exhibits either beneficial or toxic effects on plant growth and development in a low or high concentration, respectively.…”

Quick selenium accumulation in selenium-rich rice and its physiological changes in selenium environment

“…It means CAL1 may do not appear to affect selenium accumulation in rice roots. In addition, it was reported that NRT1.1B, a member of rice peptide transporter (PTR) family , holds great potential for the improvement of Se concentrations in grains by facilitating SeMet translocation, and the findings provide novel insight into the breeding of selenium-rich rice varieties [9]. Roots of Se-hyperaccumulator species have constitutively high expression of these genes, which might account for their large selenate uptake capacity [39].…”

“…For plants, some scientists believe that selenium is a beneficial element because it has many effects on plant growth and development, including regulating plant photosynthesis and respiration, reducing free radicals damage to plants, enhancing plant stress resistance, and alleviating the toxicity of heavy metals to plants [1,7]. At the same time, it can increase chlorophyll and carotenoid content in plant leaves, reduce damage caused by ultraviolet-induced oxidative stress [8], stimulate plant growth, and enhance plant tolerance or stress resistance to abiotic or biotic stresses [9]. Low selenium concentration is believed to be beneficial to plant growth and development, while high selenium concentration may be toxic to plants [10].…”

Food Fortification as a Preventive Factor of Micronutrient Deficiency

“…По оценкам экспертов до миллиарда человек во всем мире страдают дефицитом селена [40]. Селенодефицит встречается крайне редко в странах Северной Америки, Японии и некоторых частях Южной Америки, тогда как в Европе, особенно Восточной, прослеживается умеренное потребление микроэлемента.…”