Gender-determinng Genes In The Male And Female Shrub Willows (Salix Suchowensis)

Although in animals, especially in higher vertebrates, the genetic mechanism of sexdetermination has been relatively clear, but the genetic mechanism of sex determination in theplant is not entirely clear. Flowers are the reproductive organs of angiosperms, which morevaried than any other group of organisms, because of this variation, interest in plant sexualdiversity has a long and venerable history in biology. However in many sexually reproducingplant species, the majority of plants are cosexuals. The dioecious system, with separate male andfemale individuals, is of course the rule in animals, but is found in only4%of angiospermspecies. The determinants of sexual phenotype in plants are diverse. The sex determinationevolution progress which has done in mammals is something can be tracing in plants. GenusPopulus and genus Salix are members of the Salicaceae. Populus is considered as a model genusfor genetic and genomic studies in forest trees with available resource of the genome sequence ofPopulus trichocarpa. According to the studies, high degree of synteny was found between willowand poplars. Studies about populous show there is a sex determinate location on the19thchromosome, while there is no such sex chromosome diverges in morphology. Shrub kind willowjust needs2years to finish the vegetative growth and enter the reproductive stage, which is muchfaster than the genus populous which needs several years to flower. All the characteristic ofSalicaceae shows a great model for the missing pieces of sex determinate evolution.We used molecular markers to identify the relationship between willows. We developed19pairs of SSR primers,24ISSR primers,14RAPD primers at last. Results showed that theexperimental materials we picked from Xinyi closely related, and most of them were cuttingmaterial.Totally,1,201,931high quality reads were obtained, with an average length of389bp and atotal length of467.96Mb. The ESTs were assembled into29,048contigs, and132,709singletons.These unigenes were further functionally annotated by comparing their sequences to differentproteins and functional domain databases and assigned with Gene Ontology (GO) terms. Abiochemical pathway database containing291predicted pathways was also created based on theannotations of the unigenes. Digital expression analysis identified806differentially expressedgenes between the male and female flower buds. And33of them located on the incipient sexchromosome of Salicaceae, among which,12genes might involve in plant sex determinationempirically. These genes were worthy of special notification in future studies.In this study, a large number of EST sequences were generated from the flower buds of amale and a female shrub willow. We also reported the differentially expressed genes between thetwo sex-type flowers. This work provides valuable information and sequence resources for uncovering the sex determining genes and for future functional genomics analysis of Salicaceaespp.