Against the backdrop of global climate change, the frequency and intensity of drought events are on the rise, posing a severe threat to global food production and security. To address this challenge, scientists are exploring biotechnological approaches to enhance crop drought resistance. When plants face drought, they typically adopt two strategies: the “water waster” strategy, which involves maximizing growth by absorbing and utilizing as much water as possible when it is abundant, and the “water saver” strategy, which aims to prolong survival by reducing water absorption and evaporation under drought conditions. These two strategies have their own advantages and disadvantages in different environments and circumstances.
Recently, the research team led by Mohammadhossein Ravanbakhsh from Utrecht University in the Netherlands, in collaboration with Professor Xiong Wu from Nanjing Agricultural University, published a paper titled “Deletion of ACC Deaminase in Symbionts Converts the Host Plant From Water Waster to Water Saver” in the journal Plant, Cell & Environment. This study reveals that genes encoded by microorganisms may shape plant drought tolerance by regulating plant hormone balance. The research team used Arabidopsis thaliana as a model plant and a bacterium called Pseudomonas putida UW4 as a symbiotic microorganism. They constructed a simplified symbiotic model consisting of Arabidopsis and two different bacteria (wild-type and a mutant lacking ACC deaminase). ACC deaminase is an enzyme that can break down the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC), and ethylene is a key hormone in plant responses to drought. The results showed that plants symbiotic with wild-type bacteria grew faster when water was sufficient, but under drought conditions, these plants had a faster water consumption rate, leading to a shortened growth cycle and eventual death. In contrast, plants symbiotic with the mutant bacteria lacking ACC deaminase were able to reduce water consumption by closing stomata under drought conditions, thereby maintaining growth and prolonging survival. This enabled the plants to survive in severely water-deficient situations.
The research results also indicated significant differences in ethylene concentration between the two bacterial treatments. The ethylene concentration in plants lacking ACC deaminase was higher than that in the uninoculated control, and the ethylene content in the uninoculated control was higher than that in plants inoculated with wild-type bacteria. Therefore, the deletion of a single ACC deaminase gene reversed the effect of bacteria on the plant phenotype (ethylene). In addition, different bacterial treatments had significant differences in other drought resistance factors such as root-to-shoot ratio, water consumption, relative stomatal aperture, biomass per unit of water use, and stable isotopes.
This study unveils the crucial role of plant root symbiotic microorganisms in regulating plant water use strategies. Modifying the genes of symbiotic microorganisms through genetic engineering can significantly alter plant water use strategies and enhance plant drought resistance. This discovery not only provides a new perspective for plant drought resistance research but also paves a new path for the development of agricultural biotechnology.
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