Two functionally interchangeable Vps9 isoforms mediate pollen tube penetration of style

Area of Science:

• Plant reproductive biology
• Cellular and molecular biology
• Genetics

Background:

• Pollen tube penetration of the style is crucial for plant reproduction.
• Rab5 small GTPases are essential for this process in Arabidopsis.
• The guanine nucleotide exchange factor (GEF) Vps9a's role in pollen transmission was unclear due to functional redundancy.

Purpose of the Study:

• To investigate the function of Arabidopsis Vps9b in pollen tube growth.
• To elucidate the redundant mechanisms regulating pollen tube penetration.
• To understand the molecular basis of pollen tube growth failure.

Main Methods:

• Genetic analysis of Vps9a and Vps9b mutants.
• Cytological observation of pollen tube growth and cellular structures.
• Molecular analysis of protein trafficking and cellular homeostasis.

Main Results:

• Arabidopsis Vps9b is a pollen-preferential gene that functions redundantly with Vps9a.
• Vps9b is functionally interchangeable with Vps9a, with distinct expression profiles contributing to functional specialization.
• Loss of both Vps9a and Vps9b leads to mis-targeting of Rab5-dependent proteins, impaired vacuolar biogenesis, altered vesicle distribution, increased turgor, cytosolic acidification, and actin cytoskeleton disruption.
• These cellular defects collectively cause pollen tube penetration failure.

Conclusions:

• Vps9a and Vps9b form a redundant GEF system essential for pollen tube penetration.
• Disruption of this system impacts multiple cellular processes, including protein trafficking, vacuolar function, and cytoskeletal organization.
• Understanding this redundancy provides insights into plant reproductive success and potential targets for agricultural applications.