Researchers at the RIKEN Center for Sustainable Resource Science in Japan have discovered a protein which is critical for regulating plant responses to periods of dehydration. The study, published in the Proceedings of the National Academy of Sciences, shows how the protein — called NGA1 — controls transcription of a key gene without which plants would perish in the absence of water far quicker.
NGA1 is the same protein that helps your houseplants survive when you forget to water them for a couple of weeks. While you may think your plants survive your forgetfulness due to sheer resilience, their survival depends on a complex biological process involving a plant hormone called ABA. It is necessary for ABA to accumulate during early periods of dehydration and act to prevent water loss by closing pores in the plant’s leaves.
This hormone and its function are well known to modern science. However, it is not known what mechanism allows ABA to accumulate in the initial periods of dehydration. To address this, the team at RIKEN screened 1,670 transgenic plants and performed a series of tests. Their method involved using a library of plant lines created with chimeric repressor silencing technology to identify novel transcription factors in plant genetic science. This means they were looking for plants with characteristics similar to ABA-deficient mutants.
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The researchers discovered a plantline in which overexpression of NGA with a chimeric repressor domain resulted in reduced levels of the enzyme NCED3 during dehydration stress. Plants need NCED3 to produce ABA. This lead to the hypothesis that NGA was a transcription factor that could control the production of NCED3 and the synthesis of ABA.
It was eventually found that there is a whole family of NGA variants, all of which bind to the NCED3 gene that triggers its transcription. However, things get more complex from here. The RIKEN researchers also discovered that NGA proteins are found in different parts of plants and exhibit different expression patterns when the plant is dehydrated.
“Several studies have shown that increasing ABA levels can improve drought tolerance in plants,” notes Hikaru Sato, the study’s lead author. “Our finding that NGA1 is necessary for ABA biosynthesis will thus likely be helpful for developing new ways to increase drought-stress tolerance.”
The study adds that additional experiments are necessary to discover other mechanisms involved in this whole process. The team at RIKEN plans to study how changes in genetic makeup affect the molecular function of NGA1 and what factors affect its responses to varying levels of plant dehydration.