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The 2009 ASHS Annual Conference

1917:
Cloning and Characterizing Two PpSFBB-Alpha Genes In Chinese Sand Pear (Pyrus pyrifolia Nakai.)

Saturday, July 25, 2009: 5:30 PM
Laclede (Millennium Hotel St. Louis)
Lin Zhang, The key Lab. of Non-wood Forest Product of Forestry Ministry, Key Laboratory of Cultivation and Protection for Non-Wood Forest Trees, Ministry of Education, Central South University of Forestry and Technology, Changsha,410004, China
Xiao-Feng Tan, Key Laboratory of Cultivation and Protection for Non-Wood Forest Trees, Ministry of Education, Central South University of Forestry and Technology, Hunan 410004, China
Xu Zhou, Central South University of Forestry and Technology, Changsha, China
Yuan Deyi, Central South University of Forestry & Technology, Changsha, Huann, China
Donglin Zhang, Univ of Maine, Orono, ME
Gametophytic self-incompatibility (GSI) is genetically controlled mechanism to prevent inbreeding and promote out-crossing. It is controlled by a single multi-allelic S-locus, which contains two separate genes (a stylar S-RNase gene and a pollen S-gene). In gametophytic self-incompatible Japanese pear (Pyrus pyrifolia Nakai.) and apple (Malus domestica), three types of SFB genes (SFBB-alpha, SFBB-beta, and SFBB-gamma) have been isolated of which the SFBB-alpha genes were identified as the best candidates for pollen S-genes. To investigate sequence characteristics of the possible pollen S-gene and elucidate possible GSI mechanism of Chinese sand pear (P. pyrifolia), SFBB-alpha homologies in Chinese sand pear cultivars were cloned and characterized by degenerate primers, PSFBA-F and PSFBA-R, that were designed based on Japanese pear and apple SFBB-alpha sequence information. Results showed that the PSFBA-F and PSFBA-R primers successfully amplified a fragment of approximately 1,300 bp from ‘Maogong’ (S12S13), ‘Hongsucui’ (S4S12), ‘Tianchengzi’ (S7S12), and ‘Mantianhong’ (S4S12), corresponding to pear SFBB-alpha gene. A total of two distinct sequences derived from the 1,300 bp product were identified that were named PpSFBB12-alpha (P. pyrifolia SFBB12-alpha) and PpSFBB13-alpha, respectively. RT-PCR revealed that both PpSFBB-alpha genes were expressed specifically in the pollen grains. The coding region of PpSFBB12-alpha was 1,194 bp in length encoding 397 amino acids with predicted molecular weight of 45.8 kDa and isoeletric point of 5.03. The coding region of PpSFBB13-alpha was 1,179 bp in length encoding 392 amino acids with predicted molecular weight of 45.4 kDa and isoeletric point of 4.92. Both genes displayed normal structural characteristics of SFB/SLF genes, i.e. an F-box motif and four variable regions. At the deduced amino acid level, they shared 18.6% to 97.7% similarities with other SFB/SLFs of rosaceous plants. These characteristics of the two PpSFBB-alpha genes fully demonstrated that they are good candidates of pollen S-gene. Phylogenetic analysis revealed that 34 rosaceous SFB/SLFs were dived into two subfamily groups, but did not further form species subgroup. The evolutionary pattern of SFB/SLFs concurred with that of rosaceous S-RNases, suggesting that SFB/SLFs occurred after divergence of subfamily, but before the divergence of species as S-RNases in Rosaceae. The two PpSFBB-alpha sequence data should be useful for studying the interaction between SFBs and S-RNases and clarifying the mechanism of GSI at the molecular level in Chinese sand pear.
See more of: Genetics/Germplasm/Plant Breeding: Biotechnology
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