The two sides of plant resistance: growth and defense
Plants need to delicately balance growth and defense on a daily basis in order to survive. Now, Michigan State University scientists’ research displays how genes responsible for plant defense influence plant growth.
The team, led by Ian Major from the lab of plant scientist Gregg Howe, MSU Foundation professor at the MSU-DOE Plant Research Laboratory, found that a group of defense genes, called MYCs, is connected with seemingly unrelated plant developmental processes.
Plant defenses are typically kept at bay by a set of repressor genes, which saves energy and promotes growth when enemies are not present. This defense restraint is removed when a plant detects, for example, a caterpillar munching on a leaf.
Subsequently, MYC defense genes are unleashed, producing molecules that give the equivalent of indigestion, which is enough to stop most herbivores from finishing their meal.
When the scientists genetically removed MYCs from a lab plant, plant defenses went offline, which was expected. However, the plant’s leaves and roots grew faster than normal, in addition to having slightly higher photosynthesis rates.
“I think that MYCs are bona fide growth controllers themselves – they seem to slow it down,” Major said. “We are still not sure how they connect defense and growth functions.”
Part of the study’s long-term goal is to increase public understanding of plant defense systems, in order to develop tougher crops.
The USDA estimates that annual US crop losses to pests are significant, with some estimates showing up to 79 percent in lost harvest. Annual pesticide use is in the hundreds of millions of pounds, a financial drain with environmental consequences.
It has also been found that defense molecules that are harmful to caterpillars are useful for humans.
“Take flavonoids, they are antioxidants for humans,” Major said. “Other defense compounds are used in chemotherapy drugs. Then there are substances like nicotine, caffeine, or morphine. All these are managed by similar plant defense mechanisms in which MYCs play a key role.”
“Perhaps we could someday grow entire plants, stimulate their defenses and then harvest some compound for mass production.”