ESCRT components ISTL1 andLIP5 are required for tapetal function and pollen viability

Area of Science:

• Plant Biology
• Cell Biology
• Molecular Genetics

Background:

• Pollen wall assembly is vital for plant fertility, involving the delivery of sporopollenin and tryphine by tapetal cells.
• The precise mechanisms of membrane trafficking in tapetal cells during pollen development remain largely uncharacterized.

Purpose of the Study:

• To investigate the roles of late-acting endosomal sorting complex required for transport (ESCRT) components, ISTL1 and LIP5, in Arabidopsis thaliana tapetal cell function.
• To elucidate the contribution of ISTL1 and LIP5 to pollen wall formation and plant fertility.

Main Methods:

• Utilized Arabidopsis thaliana as a model organism.
• Characterized the phenotypes of plants lacking ISTL1 and LIP5, focusing on pollen exine patterns and fertility.
• Analyzed tapetal cell exocytosis, endosomal trafficking, and morphology in wild-type and mutant plants.

Main Results:

• Mutants lacking ISTL1 and LIP5 exhibited aberrant pollen exine patterns and partial pollen lethality.
• ISTL1 and LIP5 are crucial for the exocytosis of plasma membrane and secreted proteins in tapetal cells during the free microspore stage.
• These proteins are also involved in intralumenal vesicle concatenation within multivesicular endosomes and affect early endosomes/trans-Golgi networks.

Conclusions:

• ISTL1 and LIP5 play a significant, non-canonical role in tapetal exocytosis, essential for proper pollen wall development and tryphine deposition.
• The findings suggest a broader function for late ESCRT components beyond endosomal trafficking, extending to exocytosis and early endosomal pathways.