The Defense Phytohormone Signaling Network Enables Rapid, High-Amplitude Transcriptional Reprogramming during...

Area of Science:

• Plant biology
• Molecular plant pathology
• Genomics

Background:

• Plant immunity involves pattern-triggered immunity (PTI) and effector-triggered immunity (ETI).
• A phytohormone network (jasmonate, ethylene, PHYTOALEXIN-DEFICIENT4, salicylic acid) is vital for both PTI and ETI.
• The network's role in ETI transcriptional reprogramming remains largely unknown and poorly understood compared to PTI.

Purpose of the Study:

• To investigate the role of the phytohormone network in transcriptional reprogramming during effector-triggered immunity (ETI).
• To compare the network's function in ETI versus pattern-triggered immunity (PTI).
• To understand the temporal dynamics of transcriptional responses in Arabidopsis during bacterial pathogen challenge.

Main Methods:

• Generated time-series RNA-sequencing data from Arabidopsis thaliana wild-type and mutant plants.
• Challenged plants with virulent and avirulent strains of Pseudomonas syringae.
• Analyzed transcriptional reprogramming and gene coexpression network structures.

Main Results:

• Wild-type Arabidopsis showed high-amplitude transcriptional reprogramming within 4 hours of avirulent pathogen challenge.
• Mutant plants lacking key phytohormone network components exhibited similar transcriptional responses, but with a delay.
• Gene coexpression network structure was conserved between wild-type and mutant plants.

Conclusions:

• The phytohormone network is essential for rapid, high-amplitude transcriptional reprogramming during the early phase of ETI.
• In contrast to PTI, the phytohormone network's role in ETI is primarily temporal, affecting the speed rather than the qualitative nature of the response.