cGMP in ozone and NO dependent responses

Area of Science:

• Plant Physiology
• Molecular Biology
• Biochemistry

Background:

• Ozone (O3) inhibits mitochondrial respiration and activates the alternative oxidase (AOX) pathway, specifically AOX1a, in tobacco.
• Ozone exposure induces mitochondrial hydrogen peroxide (H2O2), nitric oxide (NO), and ethylene (ET) accumulation, but not jasmonic acid or 12-oxo-phytodienoic acid.
• Both NO and ET pathways mediate O3-induced AOX1a transcription, and AOX is involved in reducing reactive oxygen species (ROS) linked to plant stress.

Purpose of the Study:

• To investigate the specific cyclic guanosine monophosphate (cGMP) signatures and induction pathways downstream of ozone and nitric oxide.
• To determine the role of cGMP in the transcription of AOX1a and other downstream responses to ozone and nitric oxide.

Main Methods:

• Analysis of ozone-induced signaling pathways in tobacco plants.
• Measurement of reactive oxygen species (ROS), nitric oxide (NO), ethylene (ET), and cyclic guanosine monophosphate (cGMP) levels.
• Quantification of gene expression, including AOX1a and phenylalanine lyase (PAL) transcripts.

Main Results:

• Ozone (O3) induces AOX1a transcription via nitric oxide (NO) and ethylene (ET) dependent pathways.
• Early (<2 h) ozone and NO-induced AOX1a transcription is independent of cyclic guanosine monophosphate (cGMP).
• Late (>3 h) nitric oxide (NO) responses, such as phenylalanine lyase (PAL) transcript accumulation, are critically dependent on cGMP.

Conclusions:

• Ozone triggers distinct signaling pathways for early and late responses in plants.
• AOX1a induction by ozone is an early, cGMP-independent event.
• Later NO-mediated responses, including PAL transcript accumulation, are regulated by cGMP, highlighting its role in sustained stress signaling.