Papaver S-determinants trigger mitochondrially derived ROS production and disrupt energy metabolism in incompatible...

Area of Science:

• Plant reproductive biology
• Molecular genetics
• Biochemistry

Background:

• Self-incompatibility (SI) is a genetic mechanism preventing inbreeding in flowering plants.
• Papaver rhoeas SI involves S-determinant interaction, Ca2+ signaling, and reactive oxygen species (ROS) production.
• Understanding SI mechanisms is crucial for crop breeding and plant reproduction.

Purpose of the Study:

• To investigate the early molecular and metabolic events triggered by SI in Papaver rhoeas pollen.
• To elucidate the role of mitochondrial metabolism and ROS in the SI response.
• To characterize the signaling network leading to pollen tube growth arrest and programmed cell death (PCD).

Main Methods:

• Expression of Papaver pollen S-determinant (PrpS) in Arabidopsis thaliana to model SI.
• Utilizing a genetically encoded hydrogen peroxide (H2O2) sensor (roGFP2-Orp1).
• Measuring mitochondrial metabolism, cytosolic Ca2+ ([Ca2+]cyt), and pH dynamics.

Main Results:

• Elevated [Ca2+]cyt and cytosolic acidification trigger mitochondrial H2O2 production, membrane depolarization, and ATP depletion.
• Oxidative inactivation of GAPDH inhibits glycolysis, impacting the TCA cycle and enhancing mitochondrial disruption.
• SI rapidly arrests pollen tube growth via NADPH oxidase (RBOH)-mediated superoxide production, preceding mitochondrial ROS generation.

Conclusions:

• Early mitochondrial disruption, driven by Ca2+, pH, and redox signaling, is central to the SI response.
• Distinct ROS signatures from NADPH oxidase and mitochondria drive separate processes in SI.
• This SI mechanism rapidly disrupts energy metabolism in incompatible pollen tubes before PCD occurs.