Insights into uptake, accumulation, and subcellular distribution of selenium among eight wheat (Triticum aestivum L.) cultivars supplied with selenite and selenate

Authors: WANG, MIN - Northwest A&f University; ALI, FAYAZ - Northwest A&f University; QI, MINGXING - Northwest A&f University; PENG, QIN - Northwest A&f University; WANG, MENGKE - Northwest A&f University; Banuelos, Gary; MIAO, SHUYIN - Northwest A&f University; LI, ZHE - Northwest A&f University; DINH, QUANG TOAN - Northwest A&f University; LIANG, DONGLI - Northwest A&f University

Submitted to: Ecotoxicology and Environmental Safety
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/20/2020
Publication Date: 11/4/2020
Citation: Wang, M., Ali, F., Qi, M., Peng, Q., Wang, M., Banuelos, G.S., Miao, S., Li, Z., Dinh, Q., Liang, D. 2020. Insights into uptake, accumulation, and subcellular distribution of selenium among eight wheat (Triticum aestivum L.) cultivars supplied with selenite and selenate. Ecotoxicology and Environmental Safety. 207. Article 111544. https://doi.org/10.1016/j.ecoenv.2020.111544.
DOI: https://doi.org/10.1016/j.ecoenv.2020.111544

Interpretive Summary: Worldwide, there are between 0.5-1 billion people who are affected by some level of selenium (Se) deficiency. Selenium intake becomes a health issue when the daily intake of Se falls below the recommended daily allowance (50-200 µg), especially in wheat-dependent Asian countries. Selenium deficiencies can result in a range of health disorders, such as myxedematous endemic cretinism, growth retardation, impaired bone metabolism, and abnormalities in thyroid function. Consequently, enhancing Se content in cereal grains like wheat, a staple crop to more than one-third of the world’s population, has become a focus of research to combat malnutrition of Se in humans. Although wheat is considered a non-Se accumulator, biofortification of wheat with application of Se has been practiced with success. In this study, we evaluated eight different wheat cultivars for their abilities to take up Se when exposed to different forms of Se added at high and low rates. Grain yield, distribution of Se, tissue Se accumulation, and speciation of Se were all examined after 8 weeks of growth after supplementation. For all cultivars, results showed increased uptake of Se with increased application rate of Se, especially with selenate. Gain yields were, however, lower at higher rate of application of Se, irrespective of Se form added. In the selenite treatment, Se was mostly accumulated in roots and grains, whereas in the selenate treatment, Se was mostly accumulated in leaves and straw. Most Se was stored in the vacuole and to a lesser extent in the cell wall. This study demonstrated that wheat cultivars and Se sources are the key factors that influence Se uptake and translocation in wheat. Importantly, the isolation of Se in the vacuole played an important role in wheat’s tolerance and accumulation of Se. Further studies are needed to elucidate the bioavailability of Se from Se-enriched wheat consumed by humans.

Technical Abstract: Selenium (Se) is an essential micronutrient, however, up to 0.5-1 billion people worldwide are affected by Se deficiency. Selenium intake becomes a health issue when the daily intake of Se falls below the recommended daily allowance (50-200 µg), especially in wheat-dependent Asian countries. Improving the quality and Se concentrations in Se-enriched wheat should be a priority for any Se biofortification strategy related to cereal grains. Improvements can include managing the subcellular distribution and speciation of Se in wheat by altering Se sources and selecting more Se responsive cultivars. To evaluate for potential improvements in wheat Se biofortification, a pot experiment was conducted to investigate Se uptake and its distribution when Se was applied as selenite or selenate at low and high rates (1 and 10 mg kg-1, respectively) to eight wheat cultivars (Hengmai-5229, Jimai-22, Shaanmai-979, Shixin-618, Wanmai-52, Xiaoyan-22, Xumai-30, and Zhengmai-9023. For each cultivar, selenium’s impact was also investigated on grain yield and plant biomass. After 8 weeks of growth with added Se, results showed that biomass and grain yield significantly decreased with the application of both selenite and selenate at the high rate of application in almost all the cultivars. The grain yield and the biomass of ZM-9023 significantly (p < 0.05) increased by about 15% when a low rate of selenite was applied. The application of selenite and selenate increased the uptake of Se in each part of the wheat, especially with selenate, irrespective of the rate of application. Selenium mostly accumulated in the grain and root of wheat under selenite treatment, while more Se accumulated in leaves and straw under selenate treatment. Further investigation on the subcellular distribution of Se showed that the proportion of Se in vacuoles was significantly higher in organelle and cell walls. Meanwhile, Se6+ was the main species found in vacuoles, whereas SeMet and MeSeCys were the species predominantly stored in the organelle. This study demonstrated that wheat cultivars and Se sources as selenite or selenite are key factors that influence Se uptake and translocation in wheat. Moreover, the isolation of Se in the vacuole played an important role in Se tolerance and accumulation in wheat. In conclusion, ZM-9023 was the best cultivar to use for producing Se biofortified wheat.