Formation of pollen apertures in Arabidopsis requires an interplay between male meiosis, development of INP1-decorated plasma membrane domains, and the callose wall

Abstract

In most plant species, surfaces of pollen grains display characteristic patterns of apertures, formed by the gaps in the pollen wall exine. The aperture patterns are species-specific and tend to be very precise, with pollen of each species usually developing a certain number of apertures placed at distinct positions and acquiring specific morphology. The precision with which pollen apertures are produced suggests that developing pollen grains possess robust mechanisms that allow them to specify particular membrane domains as the future-aperture sites and to protect these sites from exine deposition. Recently, we demonstrated that formation of apertures in Arabidopsis depends on certain membrane domains attracting a novel protein, INP1, that assembles into punctate lines and helps to anchor these membrane domains to the overlying callose wall. Here we show that in the absence of male meiosis the ability of INP1 to assemble into lines at the pollen surface is compromised. However, INP1 still arrives to the pollen surface and mediates the interactions between the plasma membrane and the callose wall, potentially contributing to the formation of grossly abnormal patterns on pollen surface.

Arabidopsis Protein Kinase D6PKL3 Is Involved in the Formation of Distinct Plasma Membrane Aperture Domains on the Pollen Surface

“…INP1 exhibits diffuse cytoplasmic staining in the early stages of microsporogenesis and only starts assembling into three longitudinal punctate lines at the microspore periphery in tetrad-stage cells (Dobritsa and Coerper, 2012;Dobritsa and Reeder, 2017;Dobritsa et al, 2018). To understand the mechanism of aperture formation and the role of D6PKL3 in this process, we compared the dynamics of D6PKL3-YFP and INP1 expression and localization during pollen development.…”

“…We recently proposed that the punctate lines of INP1 might form at the outer side of the PM at the aperture domains, where INP1 may interact with both the PM and callose wall, although determining the exact subcellular locations of INP1 complexes is difficult (Dobritsa and Reeder, 2017;Dobritsa et al, 2018). To try to determine subcellular localization of the D6PKL3 puncta, we performed plasmolysis experiments on D6PKL3-YFP-expressing tetrads by incubating them in a solution of 25% sucrose.…”

Faculty Opinions recommendation of Arabidopsis protein kinase D6PKL3 is involved in the formation of distinct plasma membrane aperture domains on the pollen surface.

“…Three pieces of evidence support the conclusion that these PM domains correspond to the aperture domains. First, the positions of the lines of D6PKL3-YFP signal coincided with the positions of membrane protrusions characteristic of aperture domains (Dobritsa et al, 2018) INP1 exhibits diffuse cytoplasmic staining in the early stages of microsporogenesis and only starts assembling into three longitudinal punctate lines at the microspore periphery in tetrad-stage cells (Dobritsa and Coerper, 2012;Dobritsa and Reeder, 2017;Dobritsa et al, 2018). To understand the mechanism of aperture formation and the role of D6PKL3 in this process, we compared the dynamics of D6PKL3-YFP and INP1 expression and localization during pollen development.…”

“…Although compared with both the wild-type D6PKL3 and the D6PKL3 S415A mutant, the activity of D6PKL3 S415D toward PIN1 indeed considerably increased, it still showed no interaction with INP1 (Figure 7C). We recently proposed that the punctate lines of INP1 might form at the outer side of the PM at the aperture domains, where INP1 may interact with both the PM and callose wall, although determining the exact subcellular locations of INP1 complexes is difficult (Dobritsa and Reeder, 2017;Dobritsa et al, 2018). To try to determine subcellular localization of the D6PKL3 puncta, we performed plasmolysis experiments on D6PKL3-YFP-expressing tetrads by incubating them in a solution of 25% sucrose.…”

Sequential Deposition and Remodeling of Cell Wall Polymers During Tomato Pollen Development

“…Unlike the exine, which is composed primarily of specialized sporopollenin, the composition of intine is similar to that of other plant cell types with major components, including cellulose, pectin, and cell wall-associated proteins (Hess, 1993;Suárez-Cervera et al, 2002;Persson et al, 2007;Fang et al, 2008). The apertures, which will serve as possible sites for pollen tube initiation and pollen germination, develop a unique pollen wall, completely or partially lacking exine and, in some species, highly elaborating the intine into a specialized structure called the "Zwischenkörper" (Picken, 1984;El-Ghazaly and Jensen, 1986;Dobritsa and Reeder, 2017).…”