Dr. Min Cao | 曹珉

Iron is a vital micronutrient for all living organisms—including animals, plants, and microbes—and it plays a key role in the interactions between plants and the microbes around them. However, iron in the environment is often limited, leading to competition between plants and microbes for this essential resource. For example, harmful bacteria have evolved various tactics to steal iron from plant cells in order to grow and spread. In response, plants can adjust their internal iron management systems as part of their immune defense, reducing iron availability to the invaders. This defense strategy is known as nutritional immunity.

Nutritional immunity is an emerging concept in plant science with great potential for improving crop yields and resistance to diseases. Still, we don’t fully understand how plants balance the need to take up enough iron for their own growth while also limiting iron access to harmful microbes.

In our recent research, we discovered that plants can suppress their response to iron deficiency in specific root cells that are vulnerable to bacterial infection through the key nexus peptide IMA1. By turning off the iron-deficiency signal IMA1 in these cells, plants avoid “feeding” the wrong microbes—highlighting a close connection between nutrient signaling and immune defense.

Figure legend: IMA1 is the nexus of iron dependent nutritional immunity. In -Fe, IMA1 highly accumulates in the ground tissue of the root under; roots actively lower the rhizosphere pH and increase iron availability, but this decreases PTI responsiveness. In -Fe and flg22 treatment, IMA1 is degraded in a BTSL dependent manner. The rhizosphere pH is not decreased. In the early differentiation zone, surface dwelling CHA0 bacteria don’t affect IMA1 levels; high IMA1 levels increase bacterial colonization on the surface. When CHA0 colonizes inner root tissues at lateral root primordia cracks, IMA1 decreases in cells adjacent to this colonization.

Our group uses Arabidopsis thaliana and soybean as model plants to study how plants sense and respond to iron availability. We combine tools from genetics, molecular biology, biochemistry, and cell biology to:

• Understand how iron deficiency is detected and how the signal moves between cells and tissues;
• Uncover how plants use iron regulation as part of their immune system;
• Explore how soybean roots interact with beneficial microbes like rhizobia in the presence of iron.

Our ultimate goal is to provide scientific insights that help guide the breeding of crops with better nutrition and stronger disease resistance.