title: Molecular and genetic characterization of a self-compatible apple cultivar, 'CAU-1'.
abstract: In this study, we characterized a naturally occurring self-compatible apple cultivar, 'CAU-1' (S1S9), and studied the underlying mechanism that causes its compatibility. Analyses of both fruit set rate and seed number after self-pollination or cross-pollination with 'Fuji' (S1S9), and of pollen tube growth, demonstrated that 'CAU-1' is self-compatible. Genetic analysis by S-RNase PCR-typing of selfed progeny of 'CAU-1' revealed the presence of all progeny classes (S1S1, S1S9, and S9S9). Moreover, no evidence of S-allele duplication was found. These findings support the hypothesis that loss of function of an S-locus unlinked pollen-part mutation (PPM) expressed in pollen, rather than a natural mutation in the pollen-S gene (S1- and S9- haplotype), leads to SI breakdown in 'CAU-1'. In addition, there were no significant differences in pollen morphology or fertility between 'Fuji' and 'CAU-1'. However, we found that the effect of S1- and S9-RNase on the SI behavior of pollen could not be addressed better in 'CAU-1' than in 'Fuji'. Furthermore, we found that a pollen-expressed hexose transporter, MdHT1, interacted with S-RNases and showed significantly less expression in 'CAU-1' than in 'Fuji' pollen tubes. These findings support the hypothesis that MdHT1 may participate in S-RNase internalization during the SI process, and decrease of MdHT1 expression in 'CAU-1' hindered the release of self S-RNase into the cytoplasm of pollen tubes, thereby protecting pollen from the cytotoxicity of S-RNase, finally probably resulting in self-compatibility. Together, these findings indicate that S-locus external factors are required for gametophytic SI in the Rosaceae subtribe Pyrinae.
authors.affiliation: Laboratory of Fruit Cell and Molecular Breeding, China Agricultural University, Beijing 100193, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.affiliation: Laboratory of Fruit Cell and Molecular Breeding, China Agricultural University, Beijing 100193, China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Yang
authors.affiliation: Laboratory of Fruit Cell and Molecular Breeding, China Agricultural University, Beijing 100193, China.
authors.forename: Zhaoyu
authors.initials: Z
authors.lastname: Gu
authors.affiliation: Laboratory of Fruit Cell and Molecular Breeding, China Agricultural University, Beijing 100193, China.
authors.forename: Chuanbao
authors.initials: C
authors.lastname: Wu
authors.affiliation: Laboratory of Fruit Cell and Molecular Breeding, China Agricultural University, Beijing 100193, China.
authors.forename: Dong
authors.initials: D
authors.lastname: Meng
authors.affiliation: Laboratory of Fruit Cell and Molecular Breeding, China Agricultural University, Beijing 100193, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Yu
authors.affiliation: Laboratory of Fruit Cell and Molecular Breeding, China Agricultural University, Beijing 100193, China.
authors.forename: Qiuju
authors.initials: Q
authors.lastname: Chen
authors.affiliation: Laboratory of Fruit Cell and Molecular Breeding, China Agricultural University, Beijing 100193, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Li
authors.affiliation: College of Horticulture, Shenyang Agricultural University, Shenyang 110866, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Yuan
authors.affiliation: Institute of Pomology, Liaoning Academy of Agricultural Sciences, Yingkou 115009, China.
authors.forename: Dongmei
authors.initials: D
authors.lastname: Wang
authors.affiliation: Laboratory of Fruit Cell and Molecular Breeding, China Agricultural University, Beijing 100193, China. Electronic address: litianzhong1535@163.com.
authors.forename: Tianzhong
authors.initials: T
authors.lastname: Li
mesh_terms: D005638:Fruit / Q000235:genetics / Q000502:physiology; D005838:Genotype; D027845:Malus / Q000235:genetics* / Q000502:physiology / Q000648:ultrastructure; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D009154:Mutation; D010641:Phenotype; D000069600:Plant Breeding; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D053205:Pollen Tube / Q000235:genetics / Q000502:physiology / Q000648:ultrastructure; D054817:Pollination / Q000235:genetics; D011401:Promoter Regions, Genetic; D012098:Reproduction / Q000235:genetics
chemical_list: D009004:Monosaccharide Transport Proteins; D010940:Plant Proteins
keywords: Apple; MdHT1; Pollen-part mutation (PPM); S-RNase; Self-compatible; Single-nucleotide mutation