Origin and function of stomata in the moss Physcomitrella patens

Area of Science:

• Plant Biology
• Evolutionary Developmental Biology
• Genetics

Background:

• Stomata, crucial for plant gas exchange and hydration, evolved over 400 million years ago.
• The genetic regulation of stomatal development in non-vascular plants remains poorly understood.
• The precise function of stomata in early land plants has been debated for a century.

Purpose of the Study:

• To investigate the genetic machinery controlling stomatal development in the moss Physcomitrella patens.
• To identify key genes homologous to those regulating stomatal development in flowering plants.
• To understand the evolutionary conservation of stomatal development pathways.

Main Methods:

• Gene knockout studies in Physcomitrella patens targeting PpSMF1 and PpSCRM1.
• Protein-protein interaction assays to study PpSMF1 and PpSCRM1 binding.
• Gene complementation experiments between moss and flowering plants (Arabidopsis thaliana).

Main Results:

• PpSMF1 and PpSCRM1 are essential for stomata formation in P. patens sporophytes.
• These moss genes are orthologous to Arabidopsis transcriptional regulators of stomatal development.
• PpSMF1 and PpSCRM1 form a heterodimer, indicating conserved function in transcriptional activation.
• Mutants lacking stomata showed delayed sporophyte dehiscence, suggesting a role for stomata in this process.

Conclusions:

• The heterodimeric unit of SMF1 and SCRM1 proteins is functionally conserved for stomatal development from mosses to flowering plants.
• This study provides critical insights into the ancient genetic toolkit for stomatal formation.
• Stomata may have played a role in dehiscence in early land plant sporophytes.