Male gametic cell-specific gene expression in flowering plants, Proc. Natl. Acad. Sci. USA 96, 2554-2558

Plant Molecular Biology and Biotechnology Laboratory, Institute of Land and Food Resources, University of Melbourne, Parkville, Victoria 3052, Australia.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 04/1999; 96(5):2554-8. DOI: 10.1073/pnas.96.5.2554
Source: PubMed


The role of the male gamete-the sperm cell-in the process of fertilization is to recognize, adhere to, and fuse with the female gamete. These highly specialized functions are expected to be controlled by activation of a unique set of genes. However, male gametic cells traditionally have been regarded as transcriptionally quiescent because of highly condensed chromatin and a very reduced amount of cytoplasm. Here, we provide evidence for male gamete-specific gene expression in flowering plants. We identified and characterized a gene, LGC1, which was shown to be expressed exclusively in the male gametic cells. The gene product of LGC1 was localized at the surface of male gametic cells, suggesting a possible role in sperm-egg interactions. These findings represent an important step toward defining the molecular mechanisms of male gamete development and the cellular processes involved in fertilization of flowering plants.

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    • "Several different patterns of gene expression in the male germ lineage have been elucidated. Expression 330 of LGC1 is restricted to generative cell and sperm cells (Xu et al., 1999). When LGC1 promoter was 331 truncated, male germline specificity was lost and expression became constitutive (Singh et al., 2003). "
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    ABSTRACT: Flowering plant sperm cells transcribe a divergent and complex complement of genes. To examine promoter function, we chose an isopentenyltransferase gene known as PzIPT1. This gene is highly selectively transcribed in one sperm cell morphotype (Svn) of Plumbago zeylanica, which preferentially fuses with the central cell during fertilization and is thus a founding cell of the primary endosperm. In transgenic Arabidopsis, PzIPT1 promoter displays activity in both sperm cells and upon progressive promoter truncation from the 5'-end results in a progressive decrease in reporter production, consistent with occurrence of multiple enhancer sites. Cytokinin-dependent protein binding (CPB) motifs are identified in the promoter sequence, which respond with stimulation by cytokinin. Expression of PzIPT1 promoter in sperm cells confers specificity independently of previously reported Germline Restrictive Silencer Factor (GRSF) binding sequence. Instead, a cis-acting regulatory region consisting of two duplicated 6-bp Male Gamete Selective Activation (MGSA) motifs occurs near the site of transcription initiation. Disruption of this sequence-specific site inactivates expression of a GFP reporter gene in sperm cells. Multiple copies of the MGSA motif fused with the minimal CaMV35S promoter elements confer reporter gene expression in sperm cells. Similar duplicated MGSA motifs are also identified from promoter sequences of sperm cell-expressed genes in Arabidopsis, suggesting selective activation is possibly a common mechanism for regulation of gene expression in sperm cells of flowering plants.
    Full-text · Article · Jan 2016 · Plant physiology
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    • "These epigenetic factors continue to be a major theme in modern work as well. Promoter analysis has revealed that there are male germlineselective promoters that are activated in the generative and sperm cells (Xu et al., 1999; Okada et al., 2005a). Whereas most promoters are positively controlled, there is also evidence for a complex silencing element that controls male germline expression through a repressor that is expressed in all but male germ cells (Haerizadeh et al., 2006). "
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    ABSTRACT: The male germline of flowering plants constitutes a specialized lineage of diminutive cells initiated by an asymmetric division of the initial microspore cell that sequesters the generative cell from the pollen vegetative cell. The generative cell subsequently divides to form the two male gametes (non-motile sperm cells) that fuse with the two female gametophyte target cells (egg and central cells) to form the zygote and endosperm. Although these male gametes can be as little as 1/800th of the volume of their female counterpart, they encode a highly distinctive and rich transcriptome, translate proteins, and display a novel suite of gamete-distinctive control elements that create a unique chromatin environment in the male lineage. Sperm-expressed transcripts also include a high proportion of transposable element-related sequences that may be targets of non-coding RNA including miRNA and silencing elements from peripheral cells. The number of sperm-encoded transcripts is somewhat fewer than the number present in the egg cell, but are remarkably distinct compared to other cell types according to principal component and other analyses. The molecular role of the male germ lineage cells is just beginning to be understood and appears more complex than originally anticipated.
    Full-text · Article · Mar 2015 · Frontiers in Plant Science
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    • "). In recent years, several cDNA libraries from mature anthers of tomato, pollen of Brassica campestris, and generative cells of lily were constructed, and library screenings with northern blot analysis led to the isolation of male-gamete-specific genes, such as LAT52 and LGC1 (Twell et al., 1989; Theerakulpisut et al., 1991; Xu et al., 1998, 1999). Since large scale EST (expressed sequence tag) sequencing was not applied in these studies, the information obtained about gene expression in the male gametes was still relatively limited. "
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    ABSTRACT: In higher plants, specific cell differentiation and fate decision are controlled by differential gene expression. Cell type-specific transcriptome analysis has become an important tool for investigating cell regulatory mechanisms. In recent years, many different techniques have been developed for the isolation of specific cells and the subsequent transcriptome analysis, and considerable data are available regarding the transcriptional profiles of some specific cells. These cell type-specific transcriptome analyses hold significant promise for elucidating the gene expression linked to cellular identities and functions, and are extraordinarily important for research in functional genomics and systems biology aimed toward basic understanding of molecular networks and pathway interactions. Moreover, to reveal the critical mechanisms about sexual plant reproduction, the gamete and embryo cells have long been treated as good subjects for cell-specific transcriptome analysis, and there has been important progress in recent decades. In this review, we summarize current technologies in cell type-specific transcriptome analysis and review the applications of these technologies in research into the mechanisms of sexual reproduction in higher plants.
    Full-text · Article · Feb 2011
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