The globe will experience considerably higher temperatures as a result of global warming. Plants are particularly susceptible to these temperature variations since they cannot control their body temperature.
Plants respond to increased temperatures by instructing their root systems to develop more quickly. This results in lengthy roots that penetrate the soil to take up more nutrients and water. Although this reaction might benefit the plants in the short run, recent research indicates that it may be detrimental to people in the long run and unsustainable for the plants.
Thermomorphogenesis refers to how plants adapt their growth and development programs to high ambient temperatures.
Researchers at the Salk Institute have found that some plants respond to high temperatures by growing their roots quickly. Still, in the process, they are lowering the amounts of two critical nutrients: phosphorus and nitrogen. This means that the plants are less nutritious when eaten. Simultaneously, plants revert to slower root growth and inadequate response to higher temperatures if the soil is deficient in these nutrients.
Salk Professor Wolfgang Busch, the study’s senior author, said, “Global warming will lead to significantly increased temperatures on Earth, and plants are inevitably going to respond. The fact that higher temperatures deplete these important nutrients in plants is a real concern for the future of human and animal diets, and certainly, something we want to account for as we work to design more resilient crops.”
The process of thermomorphogenesis is how changes in environmental temperature affect plant growth and development. To learn more about this mechanism, Salk researchers examined Arabidopsis thaliana, a tiny flowering plant in the mustard family. Early research revealed that exposure to intense heat caused the shoot—the portion of the plant that is above ground—to grow longer. The Salk team was curious to know how these temperatures affected the roots of the plant and whether other crop plants, such as soybeans or rice, may react similarly.
The researchers increased the temperature and observed the roots of Arabidopsis, rice, and soybean plants to provide answers to these questions. The growth of the rice and soybean roots, as well as the roots of Arabidopsis, all accelerated in response to high temperatures. There was a catch, though: the quick growth required the soil to have enough phosphate and nitrogen.
Sanghwa Lee, first author of the study and a postdoctoral researcher in Busch’s lab, said, “Nitrogen and phosphorus are crucial for plant growth, development, and reproduction, so they are already in most fertilizers. Having connected the dots between these nutrients and thermomorphogenesis, we can now work to engineer plants and optimize fertilizers that ensure growth isn’t limited by lack of nitrogen and phosphorus in future higher temperatures.”
Two proteins in Arabidopsis, HY5, and NRT1.1, were critical in the connection between increased root growth and levels of nitrogen and phosphorus. Transcription factors, including HY5, are proteins that control when particular genes are switched “on” or “off.” The protein NRT1.1 senses nitrogen and is involved in controlling phosphorus levels and coordinating the growth of plant roots. Its genetic instructions are supervised by HY5.
HY5 and NRT1.1 cooperate to carry out thermomorphogenesis at high temperatures. However, root growth slows down when HY5 decreases NRT1.1 expression in response to a drop in nitrogen and phosphorus levels.
Both rice and soybean have similar proteins that share a common genetic ancestor with HY5 and NRT1.1. Busch says the rice and soybean versions of HY5 and NRT1.1 will require more investigation but will likely affect root growth and nutrient uptake similarly to Arabidopsis’ HY5 and NRT1.1.
“It is now clear that nitrogen and phosphorous are key in controlling root growth under the stress of higher temperatures,” says Busch. “This is going to be crucial to consider as we work to overcome the challenges that global warming poses on the large-scale production of nutritious food for a growing global population.”
To find out if the HY5 and NRT1.1 protein lookalikes in rice, soybeans, and other crops behave similarly, the researchers will examine these crops in greater detail in the future. Additionally, they will investigate methods for explicitly targeting these proteins to create crops whose roots can continue to grow without available phosphate and nitrogen.
Journal Reference:
- Lee, S., Showalter, J., Zhang, L. et al. Nutrient levels control root growth responses to high ambient temperature in plants. Nat Commun 15, 4689 (2024). DOI: 10.1038/s41467-024-49180-6