Exploring Plants’ Complex Metabolic Networks

Plants have developed intricately complex metabolic networks. Over the years, researchers have concentrated on unraveling the processes through which plants generate secondary metabolites—compounds produced to bolster their defense and survival mechanisms.

Only recently we started appreciating that the genes involved in making those specialized, secondary metabolites are being regulated. They are turned on when plants need to make secondary metabolites. And they are turned off when plants will no longer need to make them.”

Ying Li, Associate Professor, Horticulture and Landscape Architecture, Purdue University

Purdue’s Natalia Dudareva, Distinguished Professor of Biochemistry and Horticulture and Landscape Architecture, stated, “Also, secondary metabolites are often toxic to cells when they accumulate to high levels, as we saw when we manipulated the resistance of the barriers that volatile secondary metabolites have to pass through to be released into the atmosphere. However, cells sense the accumulation of these toxic compounds and downregulate genes responsible for the formation of precursors for these volatiles.”

Li and Dudavera underscore the significance of specialized metabolites in controlling the genes involved in the synthesis of chemical compounds in plants within a distinct edition of the journal Trends in Plant Science.

Dudareva serves as the Director, while Li is an affiliate of Purdue’s Center for Plant Biology, which is dedicated to advancing the comprehension of processes influencing plant biology.

We saw initial hints that the secondary metabolites themselves can be the signal to say, ‘OK, now we need to turn those genes on and off. And we almost know nothing about how metabolites are sensed by the plants and then lead to the genes turning on and off.”

Ying Li, Associate Professor, Horticulture and Landscape Architecture, Purdue University

Unraveling the intricacies of secondary metabolism poses challenges due to its high specificity to each distinct plant lineage.

In certain instances, only particular cells produce secondary metabolites at specific times for a particular plant species. Additionally, plants frequently generate metabolites in limited quantities, rendering their detection challenging. Researchers also face the task of assessing how these metabolites interact with proteins.

That allows you to say which protein can sense and bind to these metabolites. You have to be able to assay gene expression. And that is enabled by the next-generation sequencing toolkit.”

Ying Li, Associate Professor, Horticulture and Landscape Architecture, Purdue University

Li stated that gene regulation was also involved.

While a particular plant generates its distinct metabolites, “Next-gene sequencing in the last 20 years allows us to look at the genome activity of any plants,” stated Li.

Similar to numerous plant scientists, Li directed a significant portion of her research toward primary metabolism, particularly nitrogen metabolism, crucial for plant growth.

The extent of specialization in secondary metabolism was a surprising discovery for her. Despite the distinctions between primary and secondary metabolism, she noted that they appear to adhere to similar molecular-level principles.

“Secondary metabolites are important for a plant to adapt to a stressful situation. For example, during drought or pathogen attack, secondary metabolites help to fight off those stresses,” stated Li.

The significance of secondary metabolism extends to the success of pollination. While flowers attract insects, the impact of climate change raises concerns about the sustainability of the pollinator-plant relationship.

Li added, “For these reasons, there is always a dream of being able to do metabolic engineering to make plants produce more of the specialized metabolites that are good for plant survival, better resistance to a stress condition, to make medicine, or attract pollinators better,” she said.

Scientists must gain a deeper understanding of how an excess production of metabolites can disturb gene regulation. However, if this process can be appropriately disrupted at a specific location, “then we can safely produce a lot of metabolites because it doesn’t trigger the feedback regulation,” Li said.