Ethylene negatively regulates peach gummosis caused by Lasiodiplodia
theobromae by modulating the jasmonic, salicylic acid and UDP-sugar
Peach gummosis caused by Lasiodiplodia theobromae is one of the most
detrimental diseases in southern China. This disease is characterized
with necrosis and gum exudation in shoots. Ethylene (ET) is known to
induce gum formation, however its role in defense against peach fungal
gummosis and regulatory mechanism remain unclear. Here, the ET effect on
gummosis progression was investigated in peach shoots treated with ET or
ET inhibitors before L. theobromae inoculation. Peach shoot infection
induced ET production and the transcription of related genes; ET
application increased gum formation whereas ET inhibitors repressed it.
Additionally, ET treatment significantly reduced jasmonic (JA) level and
downregulated OPRs transcript, but increased salicylic acid (SA) content
and upregulated PAL expression. ET application increased arabinose
content, but decreased glucose and fructose levels. Transcripts of genes
related to UDP-sugar metabolism, sugar transporters, and cell wall
degradation were upregulated upon ET treatment, and reduced by ET
inhibitors. Therefore, ET negatively regulates symptom development in L.
theobromae-infected shoots, likely by modulating the JA/SA response and
promoting UDP-sugar metabolism and transport, and cell wall degradation
during gummosis. Our findings shed light on the molecular mechanism by
which ET orchestrates plant defense and gum formation in peach during L.