Affiliation:
1. State Key Laboratory of Rice Biology and Breeding, Ministry of Agriculture and Rural Affairs Key Lab of Molecular Biology of Crop Pathogens and Insect Pests, Zhejiang Key Laboratory of Biology and Ecological Regulation of Crop Pathogens and Insects, Institute of Insect Sciences, Zhejiang University, Hangzhou 310058, China.
2. LC-Bio Technology Co. Ltd., Hangzhou 310018, China.
Abstract
According to the plant vigor hypothesis, younger, more vigorous plants tend to be more susceptible to herbivores compared to older, mature plants, yet the molecular mechanisms underlying this dynamic remain elusive. Here, we uncover a hormonal cross-talk framework that orchestrates the age-related balance between plant growth and herbivore defense. We demonstrate that the accumulation of salicylic acid (SA), synthesized by
Nicotiana benthamiana
phenylalanine ammonia-lyase 6 (NbPAL6), dictates insect resistance in adult plants.
NbPAL6
expression is driven by the key transcription factor, NbMYB42, which is regulated by two interacting auxin response factors, NbARF18La/b. In juvenile plants, higher auxin levels activate
Nb
miR160c, a microRNA that simultaneously silences
NbARF18La/b
, subsequently reducing
NbMYB42
expression, lowering SA accumulation, and thus weakening herbivore defense. Excessive SA in juvenile plants enhances defense but antagonizes auxin signaling, impairing early growth. Our findings suggest a seesaw-like model that balances growth and defense depending on the plant’s developmental stage.
Publisher
American Association for the Advancement of Science (AAAS)