The Mechanism of Selenite Uptake by Rice Uncovered

Selenium (Se) is one of essential micronutrients for humans and animals, it is involved in a number of physiological functions in humans, such as anti-oxidants, cancer protection, and immune responses. Se is obtained primarily from plant foods, especially cereal foods, therefore, its accumulation by crop plants is of great interest.

A team led by Prof. Chengcai Chu of the State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, including the scientists from Henan University of Science and Technology, recently revealed the molecular mechanism of selenite uptake in rice.

 

The uptake of Se by plants is governed by many factors, such as the chemical state of Se in the soil, soil properties such as pH, clay content, soil mineralogy, and the concentration of competitive ions. The chemical form of Se in soil is a very important factor in the ability of plants to acquire it. The selenate form (SeO₄^2-), which mostly presents in well-aerated, neutral pH soils, is rather soluble and readily taken up by plants through sulphur transporters. However, the selenite form (SeO₃^2-), which is typically found in poor-aerated soil with acid to neutral pH, such as rice paddy field, is much more reactive with various soil minerals than selenate, making it less soluble in the soil solution. The mechanism of selenite uptake so far is not well understood.

 

Chu and colleagues found that ltn1, a rice mutant previously shown to have increased phosphate (Pi) uptake, exhibits higher selenite uptake than the wild-type, and further revealed that phosphate transporters are involved in selenite uptake.

 

Their analysis showed that the OsPT2, the most abundantly expressed Pi transporter in the roots, plays a crucial role in selenite uptake, and Se content in rice grains can be significantly increased in OsPT2-overexpressing plants. This demonstrates that selenite and Pi share similar uptake mechanisms.

 

"Rice is one of the most important staple food crops in China, application of Se foliage fertilizer is normally employed to boost the Se concentration in grains, which not only increases the production cost of Se-enriched foods, but also has a potential risk since the range between Se deficiency and toxicity for humans and animals is fairly small," says Dr. Lianhe Zhang, the first author of this paper. "Our work provides a potential strategy for breeding Se-enriched rice varieties, and also other crops."

 

Zhang L, Hu B, Li W, Che R, Deng K, Li H, Yu F, Ling H, Li Y, Chu C (2013) OsPT2, a phosphate transporter, is involved in active uptake of selenite in rice. New Phytologist. doi: 10.1111/nph.12596.