Scientists at the Japan-based RIKEN Center for Sustainable Resource Science (CSRS), in collaboration with the International Center for Tropical Agriculture (CIAT), Colombia, and the Japanese International Research Center for Agricultural Sciences (JIRCAS) have developed strains of rice resistant to drought. This transgenic rice was modified with a gene, AtGolS2, from the Arabidopsis plant, which is expressed in response to drought and salinity stress.
The study reports that transgenic rice modified with a gene from the Arabidopsis plant yield more rice than unmodified rice when subjected to stress brought by natural drought. Normally, plants adapt to drought-related stress by producing osmoprotectants — molecules like soluble sugars that help prevent water from leaving cells. Galactinol synthase (GolS) is an enzyme needed to produce one these important sugars called galactinol. In previous work, RIKEN scientists showed that Arabidopsis plants express the AtGolS2 gene in response to drought and salinity stress. “The Arabidopsis GolS2 gene was first identified with basic research at RIKEN,” explains RIKEN scientist Fuminori Takahashi. “Using it, we were able to improve resistance to drought-related stress, and increased the grain yield of rice in dry field conditions. This is one of the best model cases in which basic research knowledge has been successfully applied toward researching a resolution to a food-related problem.” he explained.
Several lines of transgenic Brazilian and African rice were created for this study that overexpress this gene and tested how well the rice grew in different conditions in different years. The results were very promising. First, they grew the different rice lines in greenhouse conditions and showed that the modified Brazilian and African rice did indeed show higher levels of galactinol than the unmodified control rice. Next, they tested tolerance to drought during the seedling growth period because this period often overlaps with seasonal drought. In order to precisely control this part of the experiment, it was conducted in a rainout shelter that allowed them to artificially create drought-like conditions. After three weeks, the modified strains had grown taller and showed less leaf-rolling, a common response to drought stress.
Drought tolerance was also confirmed at the reproductive stage in three rainout field trials in Colombia. These trials were during different seasons and different locations. Yet transgenic lines in both species of rice showed higher yield, greater biomass, lower leaf-roll over and greater fertility than the unmodified rice. Closer examination showed that five of the most promising strains had greater relative water content during drought conditions, and also used more light for photosynthesis, and contained more chlorophyll. Finally, they tested the transgenic rice over a three-year period in different natural environments. Again, several of the transgenic strains showed higher grain yield under mild and severe natural drought. In response to the timing of the availability of this rice in the market, Mr. Takahashi said, “Now, we have begun our next collaborative project, in which we will generate useful rice without GM technology. It might take 5-10 years to reach our goal, but we must keep pressing forward because droughts and climate change might get worse in the future.”
Source: sciencedaily.com (Edited)