title: Alternative splicing of the AGAMOUS orthologous gene in double flower of Magnolia stellata (Magnoliaceae).
abstract: Magnolia stellata is a woody ornamental shrub with more petaloid tepals than related plants from family Magnoliaceae. Recent studies revealed that expression changes in an AGAMOUS (AG) orthologous gene could resulted in double flowers with increased numbers of petals. We isolated three transcripts encoding different isoforms of a single AG orthologous gene, MastAG, mastag_2 and mastag_3, from M. stellata. Sequence alignments and Southern blot analyses suggested that MastAG was a single-copy gene in M. stellata genomes, and that mastag_2 and mastag_3 were abnormally spliced isoforms of MastAG. An 144bp exon skipping in MastAG results in the truncated mastag_2 protein lacking the completely I domain and 18 aa of the K1 subdomain, whereas an 165bp exon skipping of MastAG produces a truncated mastag_3 protein lacking 6 aa of the K3 subdomain and the completely C terminal region. Expression analyses showed that three alternative splicing (AS) isoforms expressed only in developing stamens and carpels. Functional analyses revealed that MastAG could mimic the endogenous AG to specify carpel identity, but failed to regulate stamen development in an Arabidopsis ag-1 mutant. Moreover, the key domain or subdomain deletions represented by mastag_2 and mastag_3 resulted in loss of C-function. However, ectopic expression of mastag_2 in Arabidopsis produced flowers with sepals converted into carpeloid organs, but without petals and stamens, whereas ectopic expression of mastag_3 in Arabidopsis could mimic the flower phenotype of the ag mutant and produced double flowers with homeotic transformation of stamens into petals and carpels into another ag flower. Our results also suggest that mastag_3 holds some potential for biotechnical engineering to create multi-petal phenotypes in commercial ornamental cultivars.
authors.affiliation: Biotechnology Research Center, China Three Gorges University, Yichang City, Hubei 443002, PR China. Electronic address: zhangb333@163.com.
authors.forename: Bo
authors.initials: B
authors.lastname: Zhang
authors.affiliation: College of Horticulture and Gardening, Yangtze University, Jingzhou City, Hubei 434025, PR China. Electronic address: zxliu77@yahoo.com.
authors.forename: Zhi-Xiong
authors.initials: ZX
authors.lastname: Liu
authors.affiliation: Biotechnology Research Center, China Three Gorges University, Yichang City, Hubei 443002, PR China. Electronic address: jiangma@aliyun.com.
authors.forename: Jiang
authors.initials: J
authors.lastname: Ma
authors.affiliation: College of Landscape Architecture, Beijing Forestry University, Beijing 100083, PR China. Electronic address: 363175145@qq.com.
authors.forename: Yi
authors.initials: Y
authors.lastname: Song
authors.affiliation: Biotechnology Research Center, China Three Gorges University, Yichang City, Hubei 443002, PR China. Electronic address: chenfj616@163.com.
authors.forename: Fa-Ju
authors.initials: FJ
authors.lastname: Chen
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D035264:Flowers / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D026161:MADS Domain Proteins / Q000235:genetics* / Q000378:metabolism; D031566:Magnolia / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D026161:MADS Domain Proteins
keywords: AGAMOUS; Alternative splicing; Double flower; Floral development; Magnolia stellata