Preliminary Study On Reproductive Genetics Of Ulva Prolifera

Ulva prolifera belongs to Ulva, Ulvaceae, Ulvales, Chlorphyta, Chlorphyceae,which is worldwide distributed and is predominantly composition of “green tide”. Inrecent years, the “green tide”-Ulva prolifera has gradually aroused worldwideattention and research with the scope and frequency of the occurrence of the greentide shows an increasing trend.In this paper, a total of135Ulva samples (46populations), including Ulvaprolifera and Ulva linza were collected from the northern Jiangsu sea area between2009-2011. Single algaes were selected to do the germ cells diffuse and statistics, andwe determined the generation-type by counting flagellum number. We found that (1)both sporophyte generation and gametophyte generation existed in one Ulva proliferagroup or Ulva linza group, and we believed that unisexual reproduction and gametesfuse reproduction caused it.(2) Quantity ratio of thalli in sporophyte generation andgametophyte generation was different in different place and time, thus we think thatthere is a continuous reproductive phenomenon in these groups.In this paper, we found a new haploid life history in Ulva prolifera. A sporophytemarked200910096were found and it can released reproductive cells with fourflagellum and negative phobophototaxis characteristic. When the thalli were mature,they could release reproductive cells with four flagellum and negativephobophototaxis whose reproductive cells can grow into haploid with out mixingtogether, by which way form a periodic life history. In this paper,(1) we determinedgerm cells’ flagellum number and phototaxis of the4generations, and found thatthese reproductive cells have four flagellum and negative phobophototaxis.(2) Wedetermined karyotype of every offspring-generation thalli, and found these thalli wereall haploid (n=8).(3) We sequenced the ITS sequence of every offspring-generationthalli, and found that all ITS sequences were the same. This study indicated that thislife history was stable, and was different with life histories found previously. In this paper, we used7Ulva prolifera groups (4single thalli in one group) toresearch their sexual reproductive pattern. We extracted genomic DNA and amplifiedrbcL sequences and ITS sequences. Four clonings were obtained in every single thallifor senqencing. In the end, we acquired142rbcL sequences and130ITS sequences,and we counted the length, variation points, information points and genetic distancewithin the group. We found that (1) rbcL sequences and ITS sequences in Ulvaprolifera have different genetypes, and clonings from a same single thalli can begathered into several branches.(2) The rbcL sequences and ITS sequences havediversity in different thalli,and they can be gathered into two main branches.Reseaches about rbcL sequences showed that amphilepsis in plastome existed duringgenerative propagation. Analysis about ITS sequences showed that amphilepsis inplastome came from karyogamy reproduction in group and between groups.