Location and comparison of the structure of SIAP3 and SIWUS genes on the sex chromosomes of Silene latifolia

Silene latifolia is a dioecious plant that has X and Y sex chromosomes. Male plants (XY) develops staminate flowers, while female plants (XX) develops pistillate flowers. The S. latifolia homologs of AP3 and WUS, which are related with the floral development in Arabidopsis thaliana, were identified to investigate the possibility of linkage to the sex chromosome. For using the DNA polymorphism of two deferent ecotypes, a male plant of K-line and a female plant of Berlin-line were crossed to obtain twenty of F1 generations. There are two copies of SIAP3 genes in S. latiolia. Using K-line specific primers for each copy, PCR was performed to reveal that they are encoded on the X chromosome (SIAP3X) and the Y chromosome (SIAP3Y), respectively. SIAP3A is 1.7kb in whole and consists of 6 exons and 5 introns. On the other hand, SIAP3Y consists of 7 exons and 6 introns and the 2nd intron stretches for 24kb in the whole gene of 26kb. The STS analysis using the large number of Y-chromosome deletion lines and FISH analysis revealed that SIAP3Y is located on the centromeric region of the q arm of the Y chromosome. A Dot plot comparing the genomic sequence between SIAP3X and SIAP3Y indicated that the sequence difference between SIAP3Y and SIAP3X is more striking than that between SIY1 and SIX1, which are neighboring to the pseudo autosomal regions (PAR). There are also two copies of SIWUS in the genome of S latifolia. Genetic and cytological mapping of SIWUS is in progress.