Triploid block

Triploid block is a phenomenon describing the formation of nonviable progeny after hybridization of flowering plants that differ in ploidy. The barrier is established in the endosperm, a nutritive tissue in the seed supporting embryo growth.[1][2] Triploid block typically happens when autopolyploidy occurs in diploid plants as a form of post-zygotic incompatibility and is hypothesized to be a one of the primary forms of reproductive isolation driving speciation of polyploids.[1]

Triploid block arises due to imbalance of imprinted genes in the endosperm. The endosperm is a product of double fertilization and typically contains maternal and paternal genomic information at a ratio of 2:1.[3] Mating between plants of differing ploidy can disrupt this balance, resulting in improper endosperm development and seed abortion.[4] Direction of the cross can be important in regards to imprinted gene dosage as it has been shown that maternal excess in the endosperm is more tolerated than paternal excess, which is highly deleterious.[5]

Triploid bridge refers to the ability of plants to overcome triploid block and is a step to forming a stable tetraploid. It is hypothesized that viable triploids enable gene flow between diploids and tetraploids in mixed populations.[6]

Triploid block can be overcome in natural or synthetic ways. Chemical treatment with 5-Azacytidine has been shown to partially overcome triploid block[7]. Polyspermy, additional fertilization of the egg cell, can also bypass triploid block to produce polyploids.[8] Additionally, mutants in flavanoid biosynthesis components in the maternal seed coat tissue have been shown to partially rescue paternal excess triploid block, though the exact mechanism for this is unknown.[9][10]

References

  1. ^ a b Köhler, C; Mittelsten Scheid, O; Erilova, A (Mar 2010). "The impact of the triploid block on the origin and evolution of polyploid plants". Trends in Genetics. 26 (3): 142–8. doi:10.1016/j.tig.2009.12.006. PMID 20089326.
  2. ^ Marks, G. E. (1966). "The Origin and Significance of Intraspecific Polyploidy: Experimental Evidence from Solanum chacoense". Evolution. 20 (4): 552–557. doi:10.2307/2406589. JSTOR 2406589. PMID 28562905.
  3. ^ Johnston, S. A.; den Nijs, T. P. M.; Peloquin, S. J.; Hanneman, R. E. (January 1980). "The significance of genic balance to endosperm development in interspecific crosses". Theoretical and Applied Genetics. 57 (1): 5–9. doi:10.1007/BF00276002. ISSN 0040-5752. PMID 24302359.
  4. ^ Köhler, Claudia; Mittelsten Scheid, Ortrun; Erilova, Aleksandra (March 2010). "The impact of the triploid block on the origin and evolution of polyploid plants". Trends in Genetics. 26 (3): 142–148. doi:10.1016/j.tig.2009.12.006. PMID 20089326.
  5. ^ Lin, Bor-Yaw (1984-05-01). "Ploidy Barrier to Endosperm Development in Maize". Genetics. 107 (1): 103–115. doi:10.1093/genetics/107.1.103. ISSN 1943-2631. PMC 1202307. PMID 17246209.
  6. ^ Henry, Isabelle M; Dilkes, Brian P; Young, Kim; Watson, Brian; Wu, Helen; Comai, Luca (2005-08-01). "Aneuploidy and Genetic Variation in the Arabidopsis thaliana Triploid Response". Genetics. 170 (4): 1979–1988. doi:10.1534/genetics.104.037788. ISSN 1943-2631. PMC 1449780. PMID 15944363.
  7. ^ Huc, Jonathan; Dziasek, Katarzyna; Pachamuthu, Kannan; Woh, Tristan; Köhler, Claudia; Borges, Filipe (2022-03-04). "Bypassing reproductive barriers in hybrid seeds using chemically induced epimutagenesis". The Plant Cell. 34 (3): 989–1001. doi:10.1093/plcell/koab284. ISSN 1040-4651. PMC 8894923. PMID 34792584.
  8. ^ Mao, Yanbo; Gabel, Alexander; Nakel, Thomas; Viehöver, Prisca; Baum, Thomas; Tekleyohans, Dawit Girma; Vo, Dieu; Grosse, Ivo; Groß-Hardt, Rita (2020-02-06). "Selective egg cell polyspermy bypasses the triploid block". eLife. 9 e52976. doi:10.7554/eLife.52976. ISSN 2050-084X. PMC 7004562. PMID 32027307.
  9. ^ Zumajo-Cardona, Cecilia; Aguirre, Manuel; Castillo-Bravo, Rosa; Mizzotti, Chiara; Di Marzo, Maurizio; Banfi, Camilla; Mendes, Marta A.; Spillane, Charles; Colombo, Lucia; Ezquer, Ignacio (2023-01-24). "Maternal control of triploid seed development by the TRANSPARENT TESTA 8 (TT8) transcription factor in Arabidopsis thaliana". Scientific Reports. 13 (1) 1316. Bibcode:2023NatSR..13.1316Z. doi:10.1038/s41598-023-28252-5. ISSN 2045-2322. PMC 9873634. PMID 36693864.
  10. ^ Dilkes, Brian P; Spielman, Melissa; Weizbauer, Renate; Watson, Brian; Burkart-Waco, Diana; Scott, Rod J; Comai, Luca (2008-12-09). Weigel, Detlef (ed.). "The Maternally Expressed WRKY Transcription Factor TTG2 Controls Lethality in Interploidy Crosses of Arabidopsis". PLOS Biology. 6 (12): 2707–2720. doi:10.1371/journal.pbio.0060308. ISSN 1545-7885. PMC 2596861. PMID 19071961.


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