Multiple developmental pathways leading to a single morph: monosulcate pollen (examples from the Asparagales)

Area of Science:

• Plant reproductive biology
• Developmental botany
• Monocot evolution

Background:

• Pollen aperture patterning is influenced by early microsporogenesis events like cytokinesis and cell wall formation.
• Monosulcate pollen, common in monocots, is often considered ancestral but can develop via different pathways.
• The Asparagales order provides a model clade for studying microsporogenesis and pollen evolution.

Purpose of the Study:

• To investigate the diversity of microsporogenesis pathways leading to monosulcate pollen in Asparagales.
• To determine if monosulcate pollen development is conserved or varied within the Asparagales clade.
• To re-evaluate the ancestral status of monosulcate pollen based on developmental pathways.

Main Methods:

• Light transmission and epifluorescence microscopy were used to examine microsporogenesis.
• Confocal microscopy confirmed centripetal cell plate formation in studied species.
• Comparative analysis across multiple Asparagales families.

Main Results:

• Microsporogenesis in Asparagales exhibits significant diversity, primarily between families.
• A conserved pattern of successive cytokinesis and centrifugal cell plate formation was confirmed for higher Asparagales.
• Centripetal cell wall formation, previously known only in eudicots, was observed in Tecophilaeaceae and Iridaceae.

Conclusions:

• Monosulcate pollen can evolve through multiple developmental routes, indicating homoplasy.
• The monosulcate character state should not be assumed ancestral without considering the specific developmental pathway.
• The ancestral developmental pathway for monosulcate pollen in monocots remains an open question.