Identification of genes expressed in the Arabidopsis female gametophyte

Abstract

SummaryThe angiosperm female gametophyte typically consists of one egg cell, two synergid cells, one central cell, and three antipodal cells. Each of these four cell types has unique structural features and performs unique functions that are essential for the reproductive process. The gene regulatory networks conferring these four phenotypic states are largely uncharacterized. As a first step towards dissecting the gene regulatory networks of the female gametophyte, we have identified a large collection of genes expressed in specific cells of the Arabidopsis thaliana female gametophyte. We identified these genes using a differential expression screen based on reduced expression in determinant infertile1 (dif1) ovules, which lack female gametophytes. We hybridized ovule RNA probes with Affymetrix ATH1 genome arrays and validated the identified genes using real-time RT-PCR. These assays identified 71 genes exhibiting reduced expression in dif1 ovules. We further validated 45 of these genes using promoter::GFP fusions and 43 were expressed in the female gametophyte. In the context of the ovule, 11 genes were expressed exclusively in the antipodal cells, 11 genes were expressed exclusively or predominantly in the central cell, 17 genes were expressed exclusively or predominantly in the synergid cells, one gene was expressed exclusively in the egg cell, and three genes were expressed strongly in multiple cells of the female gametophyte. These genes provide insights into the molecular processes functioning in the female gametophyte and can be used as starting points to dissect the gene regulatory networks functioning during differentiation of the four female gametophyte cell types.

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

“…These results indicate that expression of the pBiP1::BiP1 construct complemented the defect in fusion of the polar nuclei, and that this defect arose from the bip1 bip2 double mutation. We produced BiP1 cDNA constructs driven by the promoters of various genes expressed in specific cells of the female gametophyte (15) and used the constructs to transform b1/+ b2/b2 plants. We found that BiP1 expression in the central cell, but not in other female gametophytic cells, suppressed the seed abortion phenotype (Table S3).…”

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

“…A primary transcriptomic comparison of UP, ovules, and siliques enriched the UP and ovule data sets for stage-specific transcripts by excluding common sporophyte-expressed genes potentially involved in carpel and ovule determination, such as SEEDSTICK (STK; Rounsley et al, 1995) and SHATTERPROOF1 (SHP1; Flanagan et al, 1996), a phosphogluconolactonase (At5g24420) that is expressed in ovule integuments and in the ovary wall (Scutt et al, 2003), as well as genes involved in later stages of seed development, such as MEDEA (MEA; Vielle-Calzada et al, 1999), FERTILIZATION INDE-PENDENT SEED2 (Luo et al, 1999), and FLOWERING WAGENINGEN (Kinoshita et al, 2004). Using the parameters outlined in "Materials and Methods" and further comparison with publicly available data sets (Zimmermann et al, 2004;Tung et al, 2005;Yu et al, 2005;Steffen et al, 2007;Borges et al, 2008;Wang et al, 2008;Qin et al, 2009;Wuest et al, 2010), a total of 42 genes were considered enriched or preferentially expressed in ovules (Supplemental File S1). 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).…”

“…Using the parameters outlined in "Materials and Methods" and further comparison with publicly available data sets (Zimmermann et al, 2004;Tung et al, 2005;Yu et al, 2005;Steffen et al, 2007;Borges et al, 2008;Wang et al, 2008;Qin et al, 2009;Wuest et al, 2010), a total of 42 genes were considered enriched or preferentially expressed in ovules (Supplemental File S1). 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.…”

“…The transcriptional profiles of pollen (Becker et al, 2003;Twell, 2003, 2004;Pina et al, 2005; for review, see Becker and Feijó , 2007), embryo sac (Yu et al, 2005;Johnston et al, 2007;Jones-Rhoades et al, 2007;Steffen et al, 2007), pistil (Scutt et al, 2003;Tung et al, 2005), and embryo or seed developmental stages (Chen et al, 2001;Hennig et al, 2004;Yoshida et al, 2005, Le et al, 2010 were recently analyzed. More notably, recent progress in the isolation of Arabidopsis (Arabidopsis thaliana) gametes allowed genomewide expression profiling of purified sperm cells (Borges et al, 2008) as well as of isolated egg and central cells (Wuest et al, 2010).…”

AP1G mediates vacuolar acidification during synergid-controlled pollen tube reception

“…To confirm that synergid degeneration was not properly executed upon pollen tube arrival by AP1G loss of function, we expressed NLS-YFP under a synergid-specific promoter Pro DD39 (27). Synergid nuclei were labeled in both unfertilized wild-type and ap1g/+ ovules ( Fig.…”