Cytogenetics of plant cell and tissue cultures and their regenerates
ABSTRACT After a short introduction, the cytogenetics of plant cell and tissue cultures and their regenerates will be discussed. In the first section discussion will focus on cytogenetic conditions “in vivo”, i.e., in the original explant: (I) widespread ocurrence of polysomaty as a consequence of endoreduplication; (2) aneusomaty, an important, though rare, cause of chromosome number variation in vivo; (3) occurrence of chromosome structural changes in differentiated tissues, especially in association with aging; (4) mixoploidy and/or gene mutations, either nuclear or organellar, present as mosaics or periclinal chimeras, especially in vegetatively propagated plants. In section two the discussion will follow with nuclear processes at and during callus induction: (1) mitosis induction in diploid (haploid) and endoreduplicated cells and initiation of cell lines with different ploidy levels; (2) chromosome endoreduplication prior to mitosis induction as a mechanism of polyploidization; (3) nuclear fragmentation (amitosis) followed by mitosis, a mechanism responsible for wide chromosome number variation in cultured cells. In the third section the discussion will consider cytogenetic conditions in medium‐ and long‐term culture: (1) stability at the diploid level with emphasis on the genetic makeup of the species; (2) polyploidy, both existing and originated during culture, and its competitive ability in chromosomally heterogeneous cultures; (3) haploidy: origin and fate; (4) aneuploidy: origin, selective advantage of particular karyotypes, etc.; (5) chromosomal and gene” mutations: preexisting vs. induced during culture. In section four the discussion will focus on cell fusion and somatic hybrid cell lines. The two main aspects of protoplast fusion: (1) for gene (cytoplasm) transfer or exchange; and (2) for the production of somatic hybrids by nuclear fusion, will be treated in detail. Section five will consider cytogenetic conditions in regenerated plants. How much of the genetic variation present in in vitro cultures may be incorporated into regenerated plants? In trying to answer this question, the discussion will concern: (I) cell selection during the regeneration process via adventitious shoots or somatic embryos; (2) polyploidy and aneuploidy in regenerates; (3) chromosome number rnosaicism (aneusomaty) a rather frequent occurrence in plants regenerated via adventitious shoots and intrasomatic cell selection; (4) haploidy, diploidy, and polyploidy in pollen‐derived plants; (5) other genetic variation in regenerates; (6) an analysis of the somatic hybrid plants produced so far. Finally, section six will cover ensuring genetic stability: micropropagation. After stressing the genetic continuity of the meristem cell line in higher plants, papers will be discussed which show maintenance of genetic stability in plants developed in vitro from shoot apex cultures, from axillary buds and latent meristems in some plant parts. The review will end with concluding remarks.
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- "According to the hypothesis of Maletskii and Maletskaya (1996), plant tissue mixoploidy underlies gametophytic agamos� permy, i.e. the presence of tetraploid cell admix� tures among the bulk of diploid cells. The exist� ence of mixoploidy has been demonstrated in many plants, especially in the Chenopodiaceae including the genus Beta (Gentcheff & Gustafs� son 1939, D'Amato 1985, Carvalheira 2000). Reductional division of admixed tetraploid cells results in the formation of a diploid embryo sac with cells capable of embryogenesis. "
ABSTRACT: Astragalus gilvanensis Ranjbar & Nouri sp. nova (Fabaceae) is described and illustrated. It belongs to Astragalus sect. Incani and is endemic to Iran. Its morphological characters, meiotic chromosome number and meiotic behavior were studied. It is a mixoploid plant with the ploidy levels 2n = 2x = 16 and 2n = 4x = 32, consistent with the proposed base number of x = 8. Although the species displayed regular bivalent pairing and chromosome segregation at meiosis, some meiotic abnormalities were observed. The meiotic irregularities included the occurrence of varied degrees of sticky chromosomes in diakinesis to metaphase, laggard chromosomes in anaphase, cytomixis in prophase to telophase, asynchronous nuclei, and binuclear cells.Annales Botanici Fennici 01/2012; 48(Aug 2011):343-351. DOI:10.5735/085.048.0406 · 0.70 Impact Factor
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- "The mechanism of the somaclonal variation is poorly understood . Polyploidy is considered as a possible cause for somaclonal variation in tissue cultures , but how polyploidy is generated during tissue culture is unclear [39,42]. The presence of systemic endopolyploidy and DNA content variation within different tissues of S. plicata as revealed in this study suggests that endopolyploidy and DNA content variation in explants might be a cause for somaclonal variation in tissue culture derived orchid plantlets. "
ABSTRACT: Endopolyploidy is developmentally regulated. Presence of endopolyploidy as a result of endoreduplication has been characterized in insects, mammals and plants. The family Orchidaceae is the largest among the flowering plants. Many of the members of the orchid family are commercially micropropagated. Very little has been done to characterize the ploidy variation in different tissues of the orchid plants during development. The DNA contents and ploidy level of nuclei extracted from various tissues of a tropical terrestrial orchid Spathoglottis plicata were examined by flow cytometry. Sepals, petals and ovary tissues were found to have only a 2C (C, DNA content of the unreplicated haploid chromosome complement) peak. Columns, floral pedicels of newly open flowers and growing flower stems were observed to have an endopolyploid 8C peak in addition to 2C and 4C peaks. In developing floral pedicels, four peaks were observed for 2C, 4C, 8C and 16C. In root tips, there were 2C, 4C and 8C peaks. But in the root tissues at the region with root hairs, only a 2C peak was observed. Nuclei extracted from young leaves shown three peaks for 2C, 4C and 8C. A similar pattern was found in the vegetative tissues of both greenhouse-grown plants and tissue-cultured plantlets. In mature leaves, a different pattern of ploidy level was found at different parts of the leaves. In the leaf tips and middle parts, there were 2C and 4C peaks. Only at the basal part of the leaves, there were three peaks for 2C, 4C and 8C. Systemic variation of cellular endopolyploidy in different tissues during growth and development of Spathoglottis plicata from field-grown plants and in vitro cultures was identified. The implication of the findings was discussed.BMC Cell Biology 10/2004; 5(1):33. DOI:10.1186/1471-2121-5-33 · 2.34 Impact Factor
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- "All rights reserved. PII: S 0 1 6 8 -9 4 5 2 ( 0 0 ) 0 0 2 5 0 -8 spread among angiosperms  "
ABSTRACT: Large numbers of viable protoplasts were isolated and cultured from five pea genotypes. Calluses obtained (percent final plating efficiency (% FPE)=0.65-2.82% of initially plated protoplasts) exhibited great differences in proliferation and regeneration competence between and within genotypes. Flow cytometric analyses showed the occurrence of endoreduplication processes correlated with such differences, and could serve as a tool for the early prediction of plant regeneration competence from protoplasts. Fertile plants were produced only from calluses with a normal DNA level.Plant Science 08/2000; 156(2):177-183. DOI:10.1016/S0168-9452(00)00250-8 · 3.61 Impact Factor