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Correlation between a loss of auxin signaling and a loss of proliferation in maize antipodal cells.

Chettoor AM, Evans MM - Front Plant Sci (2015)

Bottom Line: In contrast to auxin signaling, cytokinin signaling is absent in the embryo sac and instead occurs adjacent to but outside of the antipodal cells.Mutant analysis shows a correlation between a loss of auxin signaling and a loss of proliferation of the antipodal cells.The leaf polarity mutant Laxmidrib1 causes a lack of antipodal cell proliferation coupled with a loss of DR5 and PIN1a expression in the antipodal cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Biology, Carnegie Institution for Science Stanford, CA USA.

ABSTRACT
The plant life cycle alternates between two genetically active generations: the diploid sporophyte and the haploid gametophyte. In angiosperms the gametophytes are sexually dimorphic and consist of only a few cells. The female gametophyte, or embryo sac, is comprised of four cell types: two synergids, an egg cell, a central cell, and a variable number of antipodal cells. In some species the antipodal cells are indistinct and fail to proliferate, so many aspects of antipodal cell function and development have been unclear. In maize and many other grasses, the antipodal cells proliferate to produce a highly distinct cluster at the chalazal end of the embryo sac that persists at the apex of the endosperm after fertilization. The antipodal cells are a site of auxin accumulation in the maize embryo sac. Analysis of different families of genes involved in auxin biosynthesis, distribution, and signaling for expression in the embryo sac demonstrates that all steps are expressed within the embryo sac. In contrast to auxin signaling, cytokinin signaling is absent in the embryo sac and instead occurs adjacent to but outside of the antipodal cells. Mutant analysis shows a correlation between a loss of auxin signaling and a loss of proliferation of the antipodal cells. The leaf polarity mutant Laxmidrib1 causes a lack of antipodal cell proliferation coupled with a loss of DR5 and PIN1a expression in the antipodal cells.

No MeSH data available.


Related in: MedlinePlus

PIN gene family of maize. Phylogenetic relationships of maize and Arabidopsis PIN genes. Maize PIN genes up-regulated two-fold in the embryo-sac-enriched samples (and over 0.1 FPKM) compared to the surrounding ovule tissue are indicated in red, while genes with higher expression in the surrounding ovule tissue than the embryo sac are indicated in blue. Genes indicated in orange have higher expression in the embryo sac than the surrounding ovule but either fall below the 0.1 FPKM cutoff or are only 1.5 to 2.0 fold higher in the embryo sac compared to the ovule. Gene names are according to Forestan et al. (2012).
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Figure 2: PIN gene family of maize. Phylogenetic relationships of maize and Arabidopsis PIN genes. Maize PIN genes up-regulated two-fold in the embryo-sac-enriched samples (and over 0.1 FPKM) compared to the surrounding ovule tissue are indicated in red, while genes with higher expression in the surrounding ovule tissue than the embryo sac are indicated in blue. Genes indicated in orange have higher expression in the embryo sac than the surrounding ovule but either fall below the 0.1 FPKM cutoff or are only 1.5 to 2.0 fold higher in the embryo sac compared to the ovule. Gene names are according to Forestan et al. (2012).

Mentions: To analyze the pattern of auxin signaling in the maize embryo sac, the expression pattern of two fluorescent reporters in maize were studied: a transcriptional reporter of auxin levels, DR5::RFP, and a fluorescent protein fusion for a auxin efflux carrier (GRMZM2G098643_ZmPIN1a) expressed from its native promoter, pPIN1a::PIN1a-YFP (Gallavotti et al., 2008). Maize whole embryo sac RNA-Seq data was mined to determine whether this PIN gene is likely to be expressed in the embryo sac. RNA-Seq of embryo-sac-enriched samples (with some attached nucellus) was compared to the remainder of the ovule lacking the embryo sac (Chettoor et al., 2014). ZmPIN1a, along with three other maize PIN genes, is up-regulated in the embryo sac (defined as having 2-fold higher expression in the embryo sac enriched sample compared to the surrounding ovule tissue and expression above 0.1FPKM) (Table 1 and Table S1). These four maize PIN genes fall into three different groups, 1, 10, and 8 (using the nomenclature of Forestan et al., 2012) (Figure 2). Two additional genes are two-fold higher in the embryo sac compared to the surrounding ovule but have expression below the 0.1 FPKM threshhold. One gene, GRMZM2G074267 in the clade with ZmPIN1a and AtPIN1, has the reverse expression pattern with higher expression in the surrounding ovule than the embryo sac.


Correlation between a loss of auxin signaling and a loss of proliferation in maize antipodal cells.

Chettoor AM, Evans MM - Front Plant Sci (2015)

PIN gene family of maize. Phylogenetic relationships of maize and Arabidopsis PIN genes. Maize PIN genes up-regulated two-fold in the embryo-sac-enriched samples (and over 0.1 FPKM) compared to the surrounding ovule tissue are indicated in red, while genes with higher expression in the surrounding ovule tissue than the embryo sac are indicated in blue. Genes indicated in orange have higher expression in the embryo sac than the surrounding ovule but either fall below the 0.1 FPKM cutoff or are only 1.5 to 2.0 fold higher in the embryo sac compared to the ovule. Gene names are according to Forestan et al. (2012).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4374392&req=5

Figure 2: PIN gene family of maize. Phylogenetic relationships of maize and Arabidopsis PIN genes. Maize PIN genes up-regulated two-fold in the embryo-sac-enriched samples (and over 0.1 FPKM) compared to the surrounding ovule tissue are indicated in red, while genes with higher expression in the surrounding ovule tissue than the embryo sac are indicated in blue. Genes indicated in orange have higher expression in the embryo sac than the surrounding ovule but either fall below the 0.1 FPKM cutoff or are only 1.5 to 2.0 fold higher in the embryo sac compared to the ovule. Gene names are according to Forestan et al. (2012).
Mentions: To analyze the pattern of auxin signaling in the maize embryo sac, the expression pattern of two fluorescent reporters in maize were studied: a transcriptional reporter of auxin levels, DR5::RFP, and a fluorescent protein fusion for a auxin efflux carrier (GRMZM2G098643_ZmPIN1a) expressed from its native promoter, pPIN1a::PIN1a-YFP (Gallavotti et al., 2008). Maize whole embryo sac RNA-Seq data was mined to determine whether this PIN gene is likely to be expressed in the embryo sac. RNA-Seq of embryo-sac-enriched samples (with some attached nucellus) was compared to the remainder of the ovule lacking the embryo sac (Chettoor et al., 2014). ZmPIN1a, along with three other maize PIN genes, is up-regulated in the embryo sac (defined as having 2-fold higher expression in the embryo sac enriched sample compared to the surrounding ovule tissue and expression above 0.1FPKM) (Table 1 and Table S1). These four maize PIN genes fall into three different groups, 1, 10, and 8 (using the nomenclature of Forestan et al., 2012) (Figure 2). Two additional genes are two-fold higher in the embryo sac compared to the surrounding ovule but have expression below the 0.1 FPKM threshhold. One gene, GRMZM2G074267 in the clade with ZmPIN1a and AtPIN1, has the reverse expression pattern with higher expression in the surrounding ovule than the embryo sac.

Bottom Line: In contrast to auxin signaling, cytokinin signaling is absent in the embryo sac and instead occurs adjacent to but outside of the antipodal cells.Mutant analysis shows a correlation between a loss of auxin signaling and a loss of proliferation of the antipodal cells.The leaf polarity mutant Laxmidrib1 causes a lack of antipodal cell proliferation coupled with a loss of DR5 and PIN1a expression in the antipodal cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Biology, Carnegie Institution for Science Stanford, CA USA.

ABSTRACT
The plant life cycle alternates between two genetically active generations: the diploid sporophyte and the haploid gametophyte. In angiosperms the gametophytes are sexually dimorphic and consist of only a few cells. The female gametophyte, or embryo sac, is comprised of four cell types: two synergids, an egg cell, a central cell, and a variable number of antipodal cells. In some species the antipodal cells are indistinct and fail to proliferate, so many aspects of antipodal cell function and development have been unclear. In maize and many other grasses, the antipodal cells proliferate to produce a highly distinct cluster at the chalazal end of the embryo sac that persists at the apex of the endosperm after fertilization. The antipodal cells are a site of auxin accumulation in the maize embryo sac. Analysis of different families of genes involved in auxin biosynthesis, distribution, and signaling for expression in the embryo sac demonstrates that all steps are expressed within the embryo sac. In contrast to auxin signaling, cytokinin signaling is absent in the embryo sac and instead occurs adjacent to but outside of the antipodal cells. Mutant analysis shows a correlation between a loss of auxin signaling and a loss of proliferation of the antipodal cells. The leaf polarity mutant Laxmidrib1 causes a lack of antipodal cell proliferation coupled with a loss of DR5 and PIN1a expression in the antipodal cells.

No MeSH data available.


Related in: MedlinePlus