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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

Maize ovules with mature embryo sacs. (A) Fixed and cleared ovule stained with Acriflavine (Red) and Propidium Iodide (Green). Inset shows higher magnification of antipodal cell region. (B) Live cell imaging of an ovule expressing pHistoneH1B::HISTONEH1B-YFP. (C,D) Fixed and cleared ovules stained with Acriflavine (Red) and fluorescence from formaldehyde fixation and autofluorescence (Green). a, antipodal cells; cc, central cell; e, egg cell; n, nucellus; pn, polar nuclei; s, synergid. Scale bar = 100 μm.
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Figure 1: Maize ovules with mature embryo sacs. (A) Fixed and cleared ovule stained with Acriflavine (Red) and Propidium Iodide (Green). Inset shows higher magnification of antipodal cell region. (B) Live cell imaging of an ovule expressing pHistoneH1B::HISTONEH1B-YFP. (C,D) Fixed and cleared ovules stained with Acriflavine (Red) and fluorescence from formaldehyde fixation and autofluorescence (Green). a, antipodal cells; cc, central cell; e, egg cell; n, nucellus; pn, polar nuclei; s, synergid. Scale bar = 100 μm.

Mentions: In maize and other grasses the antipodal cells are unique among embryo sac cells in proliferating after cellularization. This is one of the distinguishing features of grass embryo sacs compared to Arabidopsis, in which the antipodal cells do not proliferate. Analysis of mature embryo sacs reveals that the mature antipodal cells also have fundamental differences from other embryo sac cells. Nuclei of the antipodal cells are very distinct from those of the central cell or egg cell (the synergids have typically degenerated by maturity) and more closely resemble the surrounding nucellar cell nuclei (Figure 1). Egg cell nuclei and particularly polar nuclei have large prominent nucleoli, which stain with Acriflavine as a Periodic Acid Schiff reagent, and the nuclei overall stain faintly with Propidium Iodide. The antipodal cell nuclei, in contrast, lack prominent nucleoli and have an intense speckled staining pattern with Propidium Iodide. Additionally, the Histone H1B gene, GRMZM2G164020, is expressed in the antipodal cells and the nucellus, but not in mature central cells or egg cells (Figure 1B). Based on nuclear staining properties, nucleoli appearance, and Histone H1B expression, the antipodal cell nuclei are much more similar to the nucellar nuclei than they are to the other embryo sac nuclei.


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

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

Maize ovules with mature embryo sacs. (A) Fixed and cleared ovule stained with Acriflavine (Red) and Propidium Iodide (Green). Inset shows higher magnification of antipodal cell region. (B) Live cell imaging of an ovule expressing pHistoneH1B::HISTONEH1B-YFP. (C,D) Fixed and cleared ovules stained with Acriflavine (Red) and fluorescence from formaldehyde fixation and autofluorescence (Green). a, antipodal cells; cc, central cell; e, egg cell; n, nucellus; pn, polar nuclei; s, synergid. Scale bar = 100 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 1: Maize ovules with mature embryo sacs. (A) Fixed and cleared ovule stained with Acriflavine (Red) and Propidium Iodide (Green). Inset shows higher magnification of antipodal cell region. (B) Live cell imaging of an ovule expressing pHistoneH1B::HISTONEH1B-YFP. (C,D) Fixed and cleared ovules stained with Acriflavine (Red) and fluorescence from formaldehyde fixation and autofluorescence (Green). a, antipodal cells; cc, central cell; e, egg cell; n, nucellus; pn, polar nuclei; s, synergid. Scale bar = 100 μm.
Mentions: In maize and other grasses the antipodal cells are unique among embryo sac cells in proliferating after cellularization. This is one of the distinguishing features of grass embryo sacs compared to Arabidopsis, in which the antipodal cells do not proliferate. Analysis of mature embryo sacs reveals that the mature antipodal cells also have fundamental differences from other embryo sac cells. Nuclei of the antipodal cells are very distinct from those of the central cell or egg cell (the synergids have typically degenerated by maturity) and more closely resemble the surrounding nucellar cell nuclei (Figure 1). Egg cell nuclei and particularly polar nuclei have large prominent nucleoli, which stain with Acriflavine as a Periodic Acid Schiff reagent, and the nuclei overall stain faintly with Propidium Iodide. The antipodal cell nuclei, in contrast, lack prominent nucleoli and have an intense speckled staining pattern with Propidium Iodide. Additionally, the Histone H1B gene, GRMZM2G164020, is expressed in the antipodal cells and the nucellus, but not in mature central cells or egg cells (Figure 1B). Based on nuclear staining properties, nucleoli appearance, and Histone H1B expression, the antipodal cell nuclei are much more similar to the nucellar nuclei than they are to the other embryo sac nuclei.

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