Impact of cytomixis on meiosis, pollen viability and pollen size in wild populations of Himalayan poppy (Meconopsis aculeata Royle). J Biosci

Department of Botany, Punjabi University, Patiala, India.
Journal of Biosciences (Impact Factor: 2.06). 10/2008; 33(3):371-80. DOI: 10.1007/s12038-008-0057-0
Source: PubMed


We report the occurrence of cytomixis in wild populations of Himalayan poppy (Meconopsis aculeata Royle),which is considered to be an important and threatened medicinal plant growing in the high hills of the Himalayas. The impact of cytomixis on meiotic behaviour, reduced pollen viability and heterogeneous-sized pollen grains was also studied. Cytological studies in the seven wild populations from the high hills of Himachal Pradesh revealed that all the Himalayan populations exist uniformly at the tetraploid level (2n=56) on x=14. The phenomenon of chromatin transfer among the proximate pollen mother cells (PMCs) in six populations caused various meiotic abnormalities. Chromatin transfer also resulted in the formation of coenocytes, aneuploid, polyploid and anucleated PMCs. Among individuals that showed chromatin transfer, chromosome stickiness and interbivalent connections were frequently observed in some PMCs. The phenomenon of cytomixis in the species seems to be directly under genetic control; it affects the meiotic course considerably and results in reduced pollen viability.

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Available from: Puneet Kumar, Ph.D.
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    • "The migration of chromatin from one cell to another directly interferes with its function and development. The increase or reduction of DNA content in PMCs may cause problems in microsporogenesis and consequently failure in the formation of balanced gametes (Bellucci et al. 2003; Singhal and Kumar 2008; Ferreira et al. 2009; Kumar et al. 2010). The most common abnormalities observed were condensed micronucleus, desynapsis, chromosome stickiness, incorrect pairing, unequal segregation, laggard chromosomes, precocious migration, and chromosome bridge (Lattoo et al. 2006) as was observed in a tetraploid accession of L. alba investigated here (Table 1; Fig. 1g). "
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    ABSTRACT: Lippia alba (Verbenaceae) is an aromatic shrub recently described as a new tropical polyploid species with five distinct chromosome numbers (2n = 30, 38, 45, 60, and 90) with 2n = 30, 45, and 60 being the most frequent ones. Cytomixis is a cellular process known as the migration of genetic material mainly between meiocytes through cytoplasmic connections or cytomictic channels. This phenomenon has been reported in various plant families such as Leguminosae, Brassicaceae, Poaceae, Apocynaceae, Liliaceae, Rutaceae, and others. The transference of genetic material between pollen mother cells (PMCs), by cytomictic channels, induces the formation of unbalanced and unreduced (2n) gametes, and is considered a possible source of aneuploid and polyploid plants. Here, we describe for the first time, the occurrence of cytomixis in meiotic cells of L. alba (tetraploid cytotype) analyzing data obtained from meiotic behavior assays. In addition, the pollen size and viability were also evaluated. A high index of irregularities during meiosis was observed as well as unviable pollen with heterogeneous size. Approximately 80 % of zygotene cells showed genetic material exchange. Considering that L. alba shows different chromosome numbers, the contribution of cytomixis to cytotypes formation is also discussed.
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    • "Cytomixis was observed at certain meiotic phases, or in all stages (de Souza and Paytomixis was observed at certain meiotic phases, or in all stages (de Souza and Pawas observed at certain meiotic phases, or in all stages (de Souza and Pas observed at certain meiotic phases, or in all stages (de Souza and Paobserved at certain meiotic phases, or in all stages (de Souza and Pacertain meiotic phases, or in all stages (de Souza and Paor in all stages (de Souza and Pan all stages (de Souza and Pastages (de Souza and Pastages (de Souza and Paand Pa- Pagliarini , 1997; Pierozzi and Benatti, 1998; Malallah and Attia, 2003), more frequently in the first division (Bellucci et al., 2003; Lattoo et al., 2006). The transfer of chromatin material during microsporogenesis was considered to cause various meiosis abnormalities, reduced pollen viability and heterogeneous-sized pollen grains (Singhal and Kumar, 2008a). Here, the occurrence of cytomixis in Pinellia only during first division with low frequency might also contribute to some of the meiotic abnormalities observed, such as univalents, chromosome laggards and bridges, micronuclei, low pollen stainability, and poor seed-set, because the transfer of different amounts of chromatin resulted in the unbalanced complements of the PMCs involved. "

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    • "Knight et al. 2010), cytology (e.g. Singhal & Kumar 2008) or ploidy level (e.g. Jacob & Pierret 2000; Pradeep & Jambhale 2000). "
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    ABSTRACT: This study undertook an investigation of an important problem, so far completely overlooked in the palynological literature - to determine the optimal sample size for pollen grain morphological studies. In other words, we investigated the number of pollen grains which should be measured in order to obtain a representative mean value of a given quantitative feature which, in consequence, would make it possible to more accurately describe the pollen of a given taxon. Investigations were conducted on a sample comprising 3850 Rosa canina L. pollen grains on the basis of the length of the polar axis (P), the equatorial diameter (E) and the P/E ratio, at the flower, specimen and population levels. The size of the pollen samples analysed reflected common sample numbers employed in previous pollen morphology studies, namely from five through 10, 20, 30, 50, 100 up to 200 pollen grains. The statistical analyses performed revealed a relatively low variability in pollen grain biometric features at the levels of flower, specimen and population. At the lowest level of variability analysed, it is sufficient to take measurements of several grains to obtain values satisfactorily representing the variability within the flower level. At the level of a specimen or population, the number of grains necessary to secure representative mean values should range from 15 to 20. However, when the research objective is not only information regarding mean values of pollen grain biometric features but also the analysis of their variability (min-max), then the sample size should include approximately 30 grains. The results obtained, apart from their significance in taxonomic studies, also possess important practical significance; measurements of pollen grain biometric features are very labour-intensive and costly and, sometimes, because of difficulties in obtaining satisfactory quantities of plant material (e.g. herbarium specimens, rare species, paleopalynological collections), also very sparse.
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