Location: Corn Host Plant Resistance ResearchTitle: Aboveground to belowground herbivore defense signaling in maize: A two-way street?) Author
Submitted to: Plant Signaling and Behavior
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/2010
Publication Date: 1/1/2011
Citation: Luthe, D., Gill, T., Zhu, L., Lopez, L., Pechanova, O., Shivaji, R., Ankala, A., Williams, W.P. 2011. Aboveground to belowground herbivore defense signaling in maize: A two-way street?. Plant Signaling and Behavior. 6:126-129. Interpretive Summary: USDA-ARS scientists working at Mississippi State University developed and released several corn germplasm lines, including Mp708, that are resistant to damage by southwestern corn borer and fall armyworm. A toxic protein, a cysteine protease called Mir1-CP, rapidly accumulates in whorl leaves of Mp708 plants in response to larval feeding. When larvae ingest the protein, it damages the midgut and retards larval growth. Feeding by larvae on the leaves also causes the protein to accumulate in the roots. The roots serve as a reservoir of Mir1-CP that can be mobilized to the whorl in response to feeding by southwestern corn borer, fall armyworm, or other caterpillars. Understanding the underlying basis of plant resistance traits such as Mir1-CP enhances their value in breeding for resistant hybrids and ultimately reducing insect damage to important crop plants.
Technical Abstract: Insect pests that attempt to feed on the caterpillar-resistant maize genotype Mp708 encounter a potent, multi-pronged defense system that thwarts their invasion. First, these plants are on “constant alert” due to constitutively elevated levels of the phytohormone jasmonic acid that signals the plant to activate its defenses. The higher jasmonic acid levels trigger the expression of defense genes prior to herbivore attack so the plants are “primed” and respond with a faster and stronger defense. The second defense is the rapid accumulation of a toxic cysteine protease called Mir1-CP in the maize whorl in response to caterpillar feeding. When caterpillars ingest Mir1-CP, it damages the insect’s midgut and retards their growth. In this article, we discuss a third possible defense strategy employed by Mp708. We have shown that foliar caterpillar feeding causes Mir1-CP and defense gene transcripts to accumulate in its roots. We propose that caterpillar feeding aboveground sends a signal belowground via the phloem that results in Mir1-CP accumulation in the roots. We also postulate that the roots serve as a reservoir of Mir1-CP that can be mobilized to the whorl in response to caterpillar assault.