| Chinese cherry (Prunus. pseudocerasus L.) is a species of tetraploid in Prunus. It originates in China and has many kinds of cultivars. It's fruits are smaller, but the fruits ripe earlier than that of sweet cherry and have many fine characters, such as better quality, flavor, cool-resistance, draught-resistance, and tolerance to infertile soil. The natural self-compatibility makes Chinese cherry as the perfect material for studying the molecular basis for self-compatibility which would provide theoreticallly the significance for enriching the self-compatible mechanisms in Prunus and meanwhile help the genetic improvement and innovation of Chinese cherry. In Chinese cherry cultivar'Taixiaohongying'with S-genotype S1S2S3S4, full length SFB genes were cloned from pollen cDNA. The transcriptions of SFB genes were detected with RT-PCR, and the SFB genotypes of self-cross hybrids were identified. The main results are as follows:1. The pair of primers with start codon and end codon was designed based on Prunus SFB genes, with this pair of primers four SFB (S-haplotype-specific F-box protein) genes from pollen cDNA of Chinese cherry cultivar'Taixiaohongying'with S-genotype S1S2S3S4 were cloned. The four SFB genes have maximum identical genes with Prunus SFB genes, and are called SFB_a(1065 bp), SFB_b(1140 bp), SFB_c(1137 bp)and SFB_d (1037 bp), respectively. The accession numbers of the four genes are GQ395341(SFB_a), GQ395340(SFB_b), EU267943(SFB_c)and GQ395339 (SFB_d ).2. The putative amino acid sequences of SFB_a, SFB_b and SFB_c have typical characteristics of Prunus SFB structures: one F-box domain located in the amino terminus, two variable regions V1 and V2, and two hypervariable regions HVa and HVb. So, PpSFB_a, PpSFB_b and PpSFB_c are thought to function as normal pollen SFB genes.3. SFB_d had no intact open reading frame. In contrast to the three functional PpSFB genes, a 100 bp deletion at nucleotide positions +19 to +118 resulted in a truncated protein, which lacked the F-box domain at the N-terminus meanwhile the two variable regions V1 and V2, and two hypervariable regions HVa and HVb are present . So, SFB_d was thought to be a nonfunctional SFB mutant.4. Four pairs of specific primers were designed according to the cloned four SFB sequences, and the expressions were evaluated with RT-PCR. The result showed that SFB_a,SFB_b,SFB_cå’ŒSFB_d were transcribed with approximately the same intensity in pollen.5. The phylogenetic tree of Prunus SFBs showed the absence of independent clade of the same species SFBs indicating that he SFBs had higher interspecific sequence similarity, and the evolution and divergence of Prunus SFBs predated the Prunus speciation.6. The SFB genotypes were identified in self-cross thirty-eight hybrids of'Taixiaohongying', and only two kinds of SFB genotypes, which are SFB_cSFB_dSFB_cSFB_d and SFB_aSFB_bSFB_cSFB, are present in the hybrids. The ratio of SFB_cSFB_dSFB_cSFB_d and SFB_aSFB_b SFB_cSFB_d is 1.6:1. The genotypes SFB_aSFB_b SFB_aSFB_b,SFB_aSFB_cSFB_aSFB_c and SFB_bSFB_cSFB_bSFB_c were no present in the hybrids indicating that the diploid pollens with SFB_aSFB_b, SFB_aSFB_c and SFB_bSFB_c are self-incompatible. So, in'Taixiaohongying', the heteroallelic pollen is self-incompatible, that is, the self-compatibility in'Taixiaohongying'is not due to the competitive interaction of the heteroallelic pollen, but to the accumulation of the nonfunctional S-haplotypes which is consistent with the self-compatibility in sour cherry.
|
PDF Full Text Request