Beneficial bacterium helps plants stay fertile in the heat

How does heat affect plants?

Plants can withstand a certain amount of heat, but when temperatures become extreme, their cells begin to struggle. High temperatures can damage cell membranes, disrupt the structure of proteins, and interfere with the enzymes that plants rely on to carry out essential biological processes. Prolonged heat stress can impair the plant’s metabolism, cause harmful oxidative damage and, in severe cases, lead to cell death. 

Even a modest rise in temperature can stress plants if it lasts long enough. The consequences extend beyond plant growth: elevated temperatures can interfere with the development and viability of pollen, making fertilization more difficult. This can reduce the formation of seeds and fruits and ultimately lower crop yields. 

Beneficial bacteria associated with plants may offer additional protection by helping plants take up nutrients, regulating growth, and limiting cellular damage caused by heat. 

“Plants may survive an increase in temperature but still lose reproductive capacity,” said Anam Fatima, a KAUST PhD student and the study’s first author. “We wanted to understand whether a beneficial bacterium could protect not only plant growth under elevated temperature but also the reproductive processes that determine yield.” 

Symbiosis against heat stress 

In experiments with Arabidopsis thaliana, a small flowering plant commonly used as a model in laboratory research, the KAUST team found that plants colonized by the beneficial bacterium Enterobacter sp. SA187 performed better at elevated temperatures than plants grown without the bacterium. The colonized plants maintained stronger growth, showed 48% higher pollen viability, and exhibited improved pollen germination and reproductive performance.  

The researchers found that the bacterium helps plants respond to heat through a process involving ethylene, a gaseous plant hormone that acts as a chemical signal. Ethylene activates an enzyme called REF6, which helps regulate chromatin — the material made of DNA and proteins that packages DNA inside cells and helps control which genes are switched on. By changing chromatin structure and making it more open, REF6 can make certain genes more accessible and help activate the plant’s response to heat.  

Further experiments confirmed the importance of this pathway. Plants with disrupted ethylene signaling or lacking functional REF6 could not benefit from the bacterium. 

“What is especially interesting is that a microorganism can influence plant performance through chromatin regulation,” said KAUST Professor Heribert Hirt, who co-led the study with Kirti Shekhawat, a former research scientist in his lab. “The bacterium connects an external biological signal with the machinery that determines which plant genes are switched on.”  

The findings reveal another way beneficial bacteria can help plants cope with heat: by influencing how their genes respond to rising temperatures. Understanding these mechanisms could inform future approaches to crop protection as heat waves become more frequent. Further research is needed to determine how this strategy can translate to agricultural plants and field conditions.