Attenuation of Cf-mediated defense responses at elevated temperatures correlates with a decrease in elicitor-binding...

Area of Science:

• Plant Pathology
• Molecular Plant-Microbe Interactions
• Plant Immunity

Background:

• The interaction between tomato and Cladosporium fulvum involves a gene-for-gene system with specific resistance (Cf) and avirulence (Avr) genes.
• Plant defense responses like medium alkalization and oxidative burst are triggered by Avr elicitors in transgenic cells.

Purpose of the Study:

• To investigate the impact of elevated ambient temperatures on plant defense responses mediated by the Cf/Avr gene-for-gene system.
• To determine the temperature sensitivity of plant perception to fungal avirulence factors.

Main Methods:

• Utilized transgenic tobacco suspension cells expressing Cf genes and tomato seedlings expressing Cf/Avr genes.
• Assessed defense responses including medium alkalization, oxidative burst, and defense-related gene induction at different temperatures (20°C and 33°C).
• Quantified the abundance of the high-affinity binding site (HABS) for AVR9 on plasma membranes.

Main Results:

• Elevated temperatures (33°C) attenuated Cf/Avr-mediated defense responses in both cell suspensions and whole seedlings.
• Tomato seedlings showed systemic necrosis at normal temperatures but were rescued at 33°C.
• At 33°C, Cf/Avr-mediated defense gene induction was reversibly suppressed, and AVR-induced medium alkalization was inhibited.
• The amount of AVR9-HABS, a putative co-receptor, was significantly reduced at elevated temperatures.

Conclusions:

• Temperature sensitivity of Cf-mediated plant defense responses is linked to the perception of fungal avirulence factors.
• The reduction in AVR9-HABS at higher temperatures suggests impaired elicitor perception as the primary cause of suppressed immunity.