Study on Genomic Changes in Partial Amphiploids of Common Wheat_Wheatgrass

According to conventional theory, little genomic changes should occur in homozygous and stable amphiploids of the grass family, particularly those involving polyploid wheat as a parent. In the present study, however, extensive genomic changes were detected in two octoploid partial amphiploids of common wheat (Triticum aestivum L.)_wheatgrass (Agropyron intermedium (Host) P.B.=Elytrigia intermedia (Host) Nevski=Thinopyrum intermedium (Host) Barkworth and Dewey), namely Zhong 3 and Zhong 5, by RFLP analysis using 10 low_copy, wheat chromosome_specific sequences and 33 representative homoeologous group_specific sequences as probes. Genomic changes involved loss of wheat hybridization fragment(s) and/or acquisition of new fragment(s). Uniformity of the RFLP patterns among 5 individual plants taken respectively from Zhong 3 and Zhong 5 in two successive generations, suggested that genomic changes probably had occurred in the early few generations after octoploid amphiploid formation, and remained essentially static thereafter. The highly similar RFLP patterns between Zhong 3 and Zhong 5, which had identical genomic constitution but differed from each other due to involvement of different wheat varieties as parents imply that genomic changes were probably not at random. Possible causes for the extensive and rapid genomic changes in the newly formed plant amphiploids, as well as their implications for polyploid genome evolution and breeding application are discussed.

Novel ACTG1 mutation causing autosomal dominant non-syndromic hearing impairment in a Chinese family

γ -actin （ACTG1） gene is a cytoplasmic nonmuscle actin gene, which encodes a major cytoskeletal protein in the sensory hair cells of the cochlea. Mutations in ACTG1 were found to cause autosomal dominant, progressive, sensorineural hearing loss linked to the DFNA 20/26 locus on chromosome 17q25.3 in European and American families, respectively. In this study, a novel missense mutation （c.364A〉G; p.I122V） co-segregated with the affected individuals in the family and did not exist in the unaffected family members and 150 unrelated normal controls. The alteration of residue Ile122 was predicted to damage its interaction with actin-binding proteins, which may cause disruption of hair cell organization and function. These findings strongly suggested that the I122V mutation in ACTG1 caused autosomal dominant non-syndromic hearing impairment in a Chinese family and expanded the spectrum of ACTG1 mutations causing hearing loss.

Identification and Molecular Characterization of a Phytoplasma Associated with Pomegranate Fasciation Disease

To confirm phytoplasma infection,samples of pomegranate(Punica granatum L.)plants showing symptoms of fasciation were collected from an orchard located in Tai’an,Shandong Province,China.A fragment of approximately 1.2 kb was amplified with universal primers targeting the phytoplasma 16S r RNA gene from symptomatic pomegranate plants,while no fragment was obtained from healthy plants.The phytoplasma associated with the disease was designated as pomegranate fasciation(Po F).Two representative phytoplasma 16S r DNA gene sequences(Po F-Ch01 and Po F-Ch02)had 100%nucleotide sequence identity.The 16S r DNA sequence of Po F-Ch01 and Po F-Ch02 showed the highest similarity(99.6%)to that of‘P.granatum’phytoplasma isolate AY-PG,which belong to 16Sr I-B.Further phylogenetic analysis showed that Po F-Ch01 and Po F-Ch02 belonged to a cluster of 16Sr I subgroup members.In silico RFLP analysis indicated that Po F-Ch01 shared the highest similarity coefficient of 0.97 with reference strains of 16Sr I-B,M and N.Actual RFLP analysis of both enzymes Bst U I and Bfa I confirmed that of the virtual RFLP analysis.Combining these results,we concluded that Po F was a member of the‘Candidatus Phytoplasma asteris’group(16Sr I),and has very close relationship with 16Sr I-B subgroup.