A team of Chinese and British researchers have developed a new form of more resilient rice.
Dr Xiaorong Fan and Prof Guohua Xu, from Nanjing Agricultural University, in China, working with Dr Tony Miller, from the UK-based John Innes Centre, have developed rice crops with an improved ability to manage their pH levels, enabling them to take up significantly more nitrogen, iron and phosphorous from soil and increase yields,
The work is important because rice feeds 50% of the world’s population and has retained the ability to survive in varied conditions, including flooded paddy fields where the soggy, anaerobic conditions favour the availability of ammonium and much drier, drained soil, where increased oxygen means more nitrate is available. Another important reason why the work is significant is that nitrogen fertilizer is a major cost in growing many cereal crops and its over-use has a negative environmental impact.
The nitrogen that all plants need to grow is typically available in the form of nitrate or ammonium ions in the soil, which are taken up by the plant roots. For the plant to thrive, getting the right balance of nitrate and ammonium is important; too much ammonium and plant cells become alkaline, too much nitrate and they become acidic.
Upsetting the pH balance also means the plant’s enzymes do not work as well, affecting plant health and crop yield. The international team has been working out how rice plants can maintain pH under these changing environments.
They focused on a gene in rice called OsNRT2.3, which creates a protein involved in nitrate transport. The gene makes two slightly different versions of the protein OsNRT2.3a and OsNRT2.3b. Following tests to determine the role of both versions of the protein, the researchers found that OsNRT2.3b is able to switch nitrate transport on or off, depending on the internal pH of the plant cell.
When this ‘b’ protein was overexpressed in rice plants they were better able to buffer themselves against pH changes in their environment. This enabled them to take up much more nitrogen, as well as more iron and phosphorus. As a result, the plants gave a much higher yield of rice grain, up to 54% more yield in some trials, and their nitrogen use efficiency increased by up to 40%.
Dr Miller said: “Now that we know this particular protein found in rice plants can greatly increase nitrogen efficiency and yields, we can begin to produce new varieties of rice and other crops.
“These findings bring us a significant step closer to being able to produce more of the world’s food with a lower environmental impact.”
The new technology has been patented by PBL, the John Innes Centre’s innovation management company, and has already been licensed to three companies to develop new varieties of six different crop species. This study was funded by the Biotechnology and Biological Sciences Research Council (BBSRC) and grants from the Chinese Government.