Pollen-stigma adhesion inArabidopsis:a species-specific interaction mediated by lipophilic molecules in the pollen exine

Abstract

To investigate the nature and role of cell adhesion in plants, we analyzed the initial step of pollination in Arabidopsis: the binding of pollen grains to female stigma cells. Here we show this interaction occurs within seconds of pollination. Because it takes place prior to pollen hydration, it also requires adhesion molecules that can act in a virtually dry environment. We developed assays that monitored adhesion of populations of pollen grains and individual cells. Adhesion between pollen and stigma cells is highly selective - Arabidopsis pollen binds with high affinity to Arabidopsis stigmas, while pollen from other species fails to adhere. Initial binding is independent of the extracellular pollen coat (tryphine), indicating that adhesion molecules reside elsewhere on the pollen surface, most likely within the exine walls. Immediately after pollination, the stigma surface becomes altered at the interface, acquiring a pattern that interlocks with the exine; this pattern is evident only with pollen from Arabidopsis and its close relatives. Purified exine fragments bind to stigma cells, and biochemical analyses indicate that this specific, rapid and anhydrous adhesion event is mediated by lipophilic interactions.

Encapsulation of erythromycin and bacitracin antibiotics into natural sporopollenin microcapsules: antibacterial, cytotoxicity,in vitroandin vivorelease studies for enhanced bioavailability

“…This is somewhat similar to the de novo contacts of pollen grains to the female stigma cells which was reported to be governed possibly by specific interactions involved the lipophilic molecules on the pollen exine. 57 …”

Overcoming Pre-Fertilization Barriers in Intertribal Crosses between Anemone coronaria L. and Ranunculus asiaticus L.

“…This appressorium-like 'foot' appears to glue the pollen to the stigma, after which hydration takes place [8,20]. In Arabidopsis, it has been shown that the strength of pollen adhesion is directly proportional to the genetic distance between species [34]. In our intertribal crosses, this pollen-pistil interaction was showing no abnormalities, resulting in pollen adhesion, hydration, germination and pollen tube penetration into the stylar tissue.…”

“…In Anemone and Ranunculus, the stigma is typically dry papillated [19]. As dry stigmas do not produce exudates, pollen adhesion is largely realized by the properties of the pollen surface [34]. Adhesion relies on the interaction between pollen coat proteins and receptors in the stigma [10].…”

Arabidopsis Novel Microgametophyte Defective Mutant 1 Is Required for Pollen Viability via Influencing Intine Development in Arabidopsis

“…In flowering plants, the pollen wall is important for the success of sexual reproduction as it both protects the microgametophyte from various biotic and abiotic stresses, and also functions in cell–cell recognition during pollination ( Zinkl et al, 1999 ; Edlund et al, 2004 ). In Arabidopsis, the mature pollen wall has an intricate multi-layered structure, including the intine, exine, and tryphine ( Owen and Makaroff, 1995 ; Yue et al, 2014 ; Shi et al, 2015 ).…”