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The FRK1 mitogen-activated protein kinase kinase kinase (MAPKKK) from Solanum chacoense is involved in embryo sac and pollen development.

Lafleur E, Kapfer C, Joly V, Liu Y, Tebbji F, Daigle C, Gray-Mitsumune M, Cappadocia M, Nantel A, Matton DP - J. Exp. Bot. (2015)

Bottom Line: The fertilization-related kinase 1 (ScFRK1), a nuclear-localized mitogen-activated protein kinase kinase kinase (MAPKKK) from the wild potato species Solanum chacoense, belongs to a small group of pMEKKs that do not possess an extended N- or C-terminal regulatory domain.Megagametogenesis and microgametogenesis were affected, as megaspores did not progress beyond the functional megaspore (FG1) stage and the microspore collapsed around the first pollen mitosis.The ScFRK1 MAPKKK is thus involved in a signalling cascade that regulates both male and female gamete development.

View Article: PubMed Central - PubMed

Affiliation: Institut de recherche en biologie végétale, Département de sciences biologiques, Université de Montréal, 4101 rue Sherbrooke est, Montréal, QC H1X 2B2, Canada.

No MeSH data available.


Related in: MedlinePlus

Comparative cytological analyses of WT and Scfrk1-S1 pollen. Late prophase II/metaphase II showing 12 chromosomes in WT (A) and in transgenics plants (B). Tetrads surrounded by callose from WT plants (C) and transgenics (D). Mononucleate microspores just released from the tetrads of WT plants (E) and transgenics (F). Young binucleate WT pollen stained with lacto-acetic orcein showing generative (dark) and vegetative (pale) nuclei (G), and initiation of starch accumulation, visualized with the iodine test (H). The same developmental stage as G and H in transgenics (I, J). WT pollen grains 3 d before anthesis (K, L). The same developmental stage as K and L in transgenics (M, N). Mature WT (O) and transgenic (P) pollen stained with iodine; by this time, starch hydrolysis has been completed. Note the collapsed pollen grains in the transgenic line surrounding one viable pollen grain (P). Scale bar=20 μm.
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Figure 6: Comparative cytological analyses of WT and Scfrk1-S1 pollen. Late prophase II/metaphase II showing 12 chromosomes in WT (A) and in transgenics plants (B). Tetrads surrounded by callose from WT plants (C) and transgenics (D). Mononucleate microspores just released from the tetrads of WT plants (E) and transgenics (F). Young binucleate WT pollen stained with lacto-acetic orcein showing generative (dark) and vegetative (pale) nuclei (G), and initiation of starch accumulation, visualized with the iodine test (H). The same developmental stage as G and H in transgenics (I, J). WT pollen grains 3 d before anthesis (K, L). The same developmental stage as K and L in transgenics (M, N). Mature WT (O) and transgenic (P) pollen stained with iodine; by this time, starch hydrolysis has been completed. Note the collapsed pollen grains in the transgenic line surrounding one viable pollen grain (P). Scale bar=20 μm.

Mentions: In order to determine precisely when the pollen started to collapse, a cytological analysis of developing pollen was conducted. Microscopic observations of PMCs both at late prophase II/metaphase II of meiosis (Fig. 6A, B) and at the tetrad stage (Fig. 6C, D) revealed no differences between the WT and the Scfrk1-S1 line. Similarly, the young mononucleate microspores from Scfrk1-S1 and the WT line appeared indistinguishable (Fig. 6E, F), suggesting that the defect occurred at later stages of development. This was indeed the case since at later stages of gametogenesis the two lines started to show substantial differences. Mitosis occurred normally in the microspores of the WT, and was followed by differentiation of the generative and vegetative nuclei (Fig. 6G). In contrast, in line Scfrk1-S1, <20% of the microspores underwent the first pollen mitosis (PMI), but <1% continued their development, leading to differentiation of the generative and vegetative nuclei (Fig. 6I). In S. chacoense, microsporogenesis proceeds similarly to the microsporogenesis reported in both tomato (de Nettancourt and Eriksson, 1968) and S. verrucosum (de Nettancourt and Dijstra, 1969). In these species, starch accumulation begins shortly after PMI, while starch hydrolysis begins 2 d before anthesis and is completed by the time the flower opens. In the present study, the iodine test was used to monitor starch accumulation and hydrolysis in developing pollen. The test revealed that almost all WT young pollen started to accumulate starch just after the pollen mitosis (Fig. 6H), and starch accumulation reached a maximum 3 d before anthesis. At this time, the pollen grains appeared almost black (Fig. 6L), and only the generative nucleus remained visible with the acetocarmine stain (Fig. 6K), the vegetative nucleus being completely hidden by the starch grains. In contrast, in Scfrk1-S1 pollen, starch started to accumulate only in a limited number (<1%) of the pollen grains (Fig. 6J), most probably in those where mitosis had been completed and differentiation of the generative and vegetative nuclei had occurred. Most probably these pollen grains continued their development in a similar way to the WT (Fig 6M, N). At anthesis, almost all WT pollen appeared viable, having completed starch hydrolysis (Fig. 6O). In line Scfrk1-S1, however, >99% of the pollen appeared shrunken, with only very few grains showing a normal appearance (Fig. 6P).


The FRK1 mitogen-activated protein kinase kinase kinase (MAPKKK) from Solanum chacoense is involved in embryo sac and pollen development.

Lafleur E, Kapfer C, Joly V, Liu Y, Tebbji F, Daigle C, Gray-Mitsumune M, Cappadocia M, Nantel A, Matton DP - J. Exp. Bot. (2015)

Comparative cytological analyses of WT and Scfrk1-S1 pollen. Late prophase II/metaphase II showing 12 chromosomes in WT (A) and in transgenics plants (B). Tetrads surrounded by callose from WT plants (C) and transgenics (D). Mononucleate microspores just released from the tetrads of WT plants (E) and transgenics (F). Young binucleate WT pollen stained with lacto-acetic orcein showing generative (dark) and vegetative (pale) nuclei (G), and initiation of starch accumulation, visualized with the iodine test (H). The same developmental stage as G and H in transgenics (I, J). WT pollen grains 3 d before anthesis (K, L). The same developmental stage as K and L in transgenics (M, N). Mature WT (O) and transgenic (P) pollen stained with iodine; by this time, starch hydrolysis has been completed. Note the collapsed pollen grains in the transgenic line surrounding one viable pollen grain (P). Scale bar=20 μm.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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Figure 6: Comparative cytological analyses of WT and Scfrk1-S1 pollen. Late prophase II/metaphase II showing 12 chromosomes in WT (A) and in transgenics plants (B). Tetrads surrounded by callose from WT plants (C) and transgenics (D). Mononucleate microspores just released from the tetrads of WT plants (E) and transgenics (F). Young binucleate WT pollen stained with lacto-acetic orcein showing generative (dark) and vegetative (pale) nuclei (G), and initiation of starch accumulation, visualized with the iodine test (H). The same developmental stage as G and H in transgenics (I, J). WT pollen grains 3 d before anthesis (K, L). The same developmental stage as K and L in transgenics (M, N). Mature WT (O) and transgenic (P) pollen stained with iodine; by this time, starch hydrolysis has been completed. Note the collapsed pollen grains in the transgenic line surrounding one viable pollen grain (P). Scale bar=20 μm.
Mentions: In order to determine precisely when the pollen started to collapse, a cytological analysis of developing pollen was conducted. Microscopic observations of PMCs both at late prophase II/metaphase II of meiosis (Fig. 6A, B) and at the tetrad stage (Fig. 6C, D) revealed no differences between the WT and the Scfrk1-S1 line. Similarly, the young mononucleate microspores from Scfrk1-S1 and the WT line appeared indistinguishable (Fig. 6E, F), suggesting that the defect occurred at later stages of development. This was indeed the case since at later stages of gametogenesis the two lines started to show substantial differences. Mitosis occurred normally in the microspores of the WT, and was followed by differentiation of the generative and vegetative nuclei (Fig. 6G). In contrast, in line Scfrk1-S1, <20% of the microspores underwent the first pollen mitosis (PMI), but <1% continued their development, leading to differentiation of the generative and vegetative nuclei (Fig. 6I). In S. chacoense, microsporogenesis proceeds similarly to the microsporogenesis reported in both tomato (de Nettancourt and Eriksson, 1968) and S. verrucosum (de Nettancourt and Dijstra, 1969). In these species, starch accumulation begins shortly after PMI, while starch hydrolysis begins 2 d before anthesis and is completed by the time the flower opens. In the present study, the iodine test was used to monitor starch accumulation and hydrolysis in developing pollen. The test revealed that almost all WT young pollen started to accumulate starch just after the pollen mitosis (Fig. 6H), and starch accumulation reached a maximum 3 d before anthesis. At this time, the pollen grains appeared almost black (Fig. 6L), and only the generative nucleus remained visible with the acetocarmine stain (Fig. 6K), the vegetative nucleus being completely hidden by the starch grains. In contrast, in Scfrk1-S1 pollen, starch started to accumulate only in a limited number (<1%) of the pollen grains (Fig. 6J), most probably in those where mitosis had been completed and differentiation of the generative and vegetative nuclei had occurred. Most probably these pollen grains continued their development in a similar way to the WT (Fig 6M, N). At anthesis, almost all WT pollen appeared viable, having completed starch hydrolysis (Fig. 6O). In line Scfrk1-S1, however, >99% of the pollen appeared shrunken, with only very few grains showing a normal appearance (Fig. 6P).

Bottom Line: The fertilization-related kinase 1 (ScFRK1), a nuclear-localized mitogen-activated protein kinase kinase kinase (MAPKKK) from the wild potato species Solanum chacoense, belongs to a small group of pMEKKs that do not possess an extended N- or C-terminal regulatory domain.Megagametogenesis and microgametogenesis were affected, as megaspores did not progress beyond the functional megaspore (FG1) stage and the microspore collapsed around the first pollen mitosis.The ScFRK1 MAPKKK is thus involved in a signalling cascade that regulates both male and female gamete development.

View Article: PubMed Central - PubMed

Affiliation: Institut de recherche en biologie végétale, Département de sciences biologiques, Université de Montréal, 4101 rue Sherbrooke est, Montréal, QC H1X 2B2, Canada.

No MeSH data available.


Related in: MedlinePlus