A putative tetrasporophyte-specific gene,designated as SSH466(GenBank accession No. DQ019223) ,was one of the genes identified in this work using suppression subtractive hybridization(SSH) method in Gracilaria lemaneiformis. The full length of the gene was obtained using SMART RACE strategy. Sequence analysis revealed that the gene had 1 019 nucleotides,including an open reading frame of 498 nucleotides encoding 166 amino acid residues,158 nucleotides of 5' untranslated region and 363 nucleotides of 3' non-coding region. Protein motif and secondary structure prediction showed that there existed a transmembrane domain with a unique β-sheet. Thus,SSH466 protein might be a cross-membrane protein. Sequence homology search in the public GenBank databases did not reveal any significant match with SSH466. Virtual Northern blot analysis confirmed that it was a tetrasporophyte-specific gene.
Reproductive apparatus of Gracilaria/Gracilariopsis lemaneiformis collected from Qingdao city were studied with a light and a transmission electron microscope. The special superficial arrangement of spermatangium for this species was clearly observed, and the ultrastructure of spermatangial devel-opment revealed the similar cytodynamic pattern followed by all the Gracilariaceae members devel-oped from spermatangial mother cells to spermatangium. The female reproductive apparatus before fertilization was also observed and trichogyne was found protruding above the cortex, contrary to the earlier reports. Tetrasporangium was formed by an outer cortical cell and the tetraspores became spherical and expended after being released.
XU Di1, ZHU JianYi2, HE Yang1, CHENG XiaoJie1, ZHANG WenYan1 & ZHANG XueCheng1 1 College of Life Sciences, Ocean University of China, Qingdao 266003, China
