The Central Cell Plays a Critical Role in Pollen Tube Guidance inArabidopsis

Abstract

The sperm cell of flowering plants cannot migrate unaided and must be transported by the pollen tube cell of the male gametophyte to achieve successful fertilization. Long-distance pollen tube guidance is controlled by the seven-celled female gametophyte, the embryo sac. Previous reports showed that the synergid cell of the embryo sac is essential for pollen tube guidance. Here, we report the identification of a central cell guidance (ccg) mutant, which is defective in micropylar pollen tube guidance. CCG encodes a nuclear protein with an N-terminal conserved zinc β-ribbon domain that is functionally interchangeable with that of TFIIB in yeast. This suggests that CCG might act as a transcription regulator for pollen tube guidance. CCG is expressed in the central cell of the female gametophyte. Expression of CCG in the central cell alone is sufficient to restore the normal pollen tube guidance phenotype, demonstrating that the central cell plays a critical role in pollen tube guidance.

Truncation of a Protein Disulfide Isomerase, PDIL2-1, Delays Embryo Sac Maturation and Disrupts Pollen Tube Guidance inArabidopsis thaliana

“…Protein fusion reporter results also support that PDIL2-1 affects sporophytic tissues, since in ovules, PDIL2-1-YFP was expressed only in sporophytic tissues, but not in the embryo sac. The female gametophyte has been proposed as the source of a guidance signal for the pollen tube, and this is supported by genetic analysis and in vitro laser ablation experiments (Hulskamp et al, 1995;Ray et al, 1997;Higashiyama et al, 2003;Chen et al, 2007). The female gametophyte has no or a trivial effect on the development of surrounding sporophytic tissues, since ovules without embryo sacs had normal sporophyte structures (Bhatt et al, 1999;Yang et al, 1999).…”

“…The gametophytic phase, after the tube appears on the placental surface in the ovary, can be further divided into funicular guidance (Shimizu and Okada, 2000) and micropylar guidance (Higashiyama et al, 1998(Higashiyama et al, , 2001. Sporophytic tissues play some role in funicular guidance (Baker et al, 1997;Palanivelu et al, 2003), while the synergid cells (Higashiyama et al, 2001;Punwani et al, 2007) and central cell (Chen et al, 2007) are required for micropylar guidance.…”

BiP-mediated polar nuclei fusion is essential for the regulation of endosperm nuclei proliferation in Arabidopsis thaliana

“…Several A. thaliana mutants that are defective in the fusion of polar nuclei were also reported to be defective in other processes before fertilization (3,4,6). For example, pollen tube guidance into the ovule was affected in the maa mutants (3), and a role for the central cell in pollen tube guidance has been proposed (16). We therefore analyzed pollen tube guidance in b1/+ b2/b2 plants, using pollen from a transgenic line expressing a β-glucuronidase (GUS) construct driven by the BiP1 promoter, which is expressed in the pollen tubes.…”

Whole Genome Analysis of Gene Expression Reveals Coordinated Activation of Signaling and Metabolic Pathways during Pollen-Pistil Interactions in Arabidopsis

“…As anticipated, 27 out of 42 transcripts preferentially expressed in ovules and 96 out of 1,275 ovule-enriched transcripts were previously reported to be expressed specifically in the embryo sac or enriched in female gametophytic cells (Supplemental File S1; Yu et al, 2005;Johnston et al, 2007;Punwani et al, 2007;Steffen et al, 2007;Wuest et al, 2010). Ovule-expressed transcripts likely include plausible candidates for shortrange pollen tube attractants expressed in the embryo sac (Higashiyama et al, 2001(Higashiyama et al, , 2003Chen et al, 2007;Okuda et al, 2009) but also of other modulators expressed in the surrounding sporophytic tissues that could function as long-range pollen tube attractants. UP express the lowest number of enriched transcripts (340), due to the exclusion of overlapping transcript expression with mature siliques.…”