Coronatine inhibits mesocotyl elongation by promoting ethylene production in etiolated maize seedlings

Abstract

Maize (Zea mays L.) is one of the most important cereal crops in the world. In order to survive, plants must regulate their growth in response to multiple developmental and environmental cues, including modulating lodging stress. Coronatine is a chlorosis-inducing non-host-specific phytotoxin produced by several members of the Pseudomonas syringe group of pathovars, which can lead to leaf chlorosis, anthocyanin production, and growth inhibition. In this study, we investigated the physiological mechanism for coronatine during maize mesocotyl growth and development. Using ethephon as a positive control, we found that coronatine inhibited the elongation of mesocotyls in maize B73 etiolated seedlings which was related to ethylene production. Both coronatine and ethephon increased mesocotyls coarsening by increasing the cell diameter and shortened it by inhibiting cell elongation. Coronatine also thickened cell walls in longitudinal and transverse sections by increasing the expression of the cellulose lignin synthesis gene ZmEXT. To further verify the correlation between coronatine and ethephon during mesocotyl growth, we detected the release of endogenous ethylene and the expression of ZmACOs and ZmACSs. We found that coronatine increased the ethylene production while inhibiting auxin synthesis, thereby inhibiting mesocotyl growth.