Sex determination in plants
Evolutionary transitions happened gradually from hermaphroditism to monoec in which multiple sex determining genes are involved which include male-sterility and female-sterility factors. There should not be any recombination between different loci which is the pivotal reason for the genetic degeneration of Y chromosomes. There are several theories attached to Y chromosome degeneration that are reviewed recently .
Introduction: why are plant sex chromosomes of particular interest? Sex inheritance and sex chromosomes in plants are similar to those in animals. In many sexually reproducing plant species all individuals are 'sexually monomorphic' or hermaphroditic.The term 'cosexual' is used when individual plants have both sex functions, whether present within each flower (hermaphrodite), or in separate male and female flowers (monoecious). Dioecious species are 'sexually polymorphic', with separate males and females but their hermaphrodite relatives have rudiments of opposite sex structures in flowers of each sex,suggesting recent evolution of unisexual flowers. The low frequency and scattered taxonomic distribution of dioecy and sex chromosomes indicates cosexuality is the ancestral angiosperm state and sex chromosomes evolved repeatedly and quite recently.
In Silene ( Family Caryophyllaceae) some species are gynodioecious and others are hermaphroditic. ITS sequences of nuclear ribosomal RNA genes of Silene species indicates two origins of dioecy.Molecular clock datas suggest an age of < 20 million years for the heteromorphic sex chromosomes of the species Silene latifolia and S. dioica which means separate sexes may have evolved more than 100 times in the flowering plants, given that 160 families have dioecious members and they have short evolutionary lives.
The genetics of sex determination in plants, and plant sex chromosomes In dioecious plants, males are 'inconstant', ie produce occasional...
Please join StudyMode to read the full document