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Genetics of dioecy and causal sex chromosomes in plants

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Title Genetics of dioecy and causal sex chromosomes in plants
 
Creator Kumar, Sushil
Kumari, Renu
Sharma, Vishakha
 
Subject dioecy-mediated species evolution
plant unisexuality
sex-chromosome evolution
sex-ratio variation
XY–WZ transition
Y-chromosome degeneration
 
Description Accepted date: 5 September 2013
Dioecy (separate male and female individuals) ensures outcrossing and is more prevalent in animals than in plants. Although it is common in bryophytes and gymnosperms, only 5% of angiosperms are dioecious. In dioecious higher plants, flowers borne on male and female individuals are, respectively deficient in functional gynoecium and androecium. Dioecy is inherited via three sex chromosome systems: XX/XY, XX/X0 and WZ/ZZ, such that XX or WZ is female and XY, X0 or ZZ are males. The XX/XY system generates the rarer XX/X0 and WZ/ZZ systems. An autosome pair begets XY chromosomes. A recessive loss-of-androecium mutation (ana) creates X chromosome and a dominant gynoecium-suppressing (GYS) mutation creates Y chromosome. The ana/ANA and gys/GYS loci are in the sex-determining region (SDR) of the XY pair. Accumulation of inversions, deleterious mutations and repeat elements, especially transposons, in the SDR of Y suppresses recombination between X and Y in SDR, making Y labile and increasingly degenerate and heteromorphic from X. Continued recombination between X and Y in their pseudoautosomal region located at the ends of chromosomal arms allows survival of the degenerated Y and of the species. Dioecy is presumably a component of the evolutionary cycle for the origin of new species. Inbred hermaphrodite species assume dioecy. Later they suffer degenerate-Y-led population regression. Cross-hybridization between such extinguishing species and heterologous species, followed by genome duplication of segregants from hybrids, give rise to new species.
Grateful thanks are due to Indian National Science Academy for the
grant of position of Honorary Scientistship to SK.
 
Date 2015-12-17T09:16:33Z
2015-12-17T09:16:33Z
2014
 
Type Article
 
Identifier J. Genet., 93(1): 241-277
0022-1333
http://172.16.0.77:8080/jspui/handle/123456789/426
http://www.ias.ac.in/listing/articles/jgen/093/01
 
Language en_US
 
Publisher Indian Academy of Sciences