Characterization of Two <i>AGL6</i>–Like Genes from a Chinese Endemic Woody Tree, <i>Manglietia patungensis</i> (Magnoliaceae) Provides Insight into Perianth Development and Evolution in Basal Angiosperms

• Main Authors: Zhixiong Liu, Kebin Zhang, Laiyun Li, Yue Fei, Faju Chen
• Format: Article
• Language: English
• Published: MDPI AG 2019-08-01
• Series: Forests
• Subjects: <i>AGAMOUS-LIKE6</i>; floral development; <i>Manglietia patungensis</i>; MADS-box gene; perianth
• Online Access: https://www.mdpi.com/1999-4907/10/8/669

<i>Manglietia patungensis</i> (Magnoliaceae) exhibits radially symmetric flowers with perianth consisting of three separate sepaloid tepals in whorl 1 and six petaloid tepals in the inner two whorls, which shows an obvious difference from flowers of most Magnoliaceae species that contain three uniform petaloid tepals whorls, and make it an excellent model for understanding perianth morphology differentiation during early flower evolution. Here, two <i>AGL6</i> orthologs, <i>MapaAGL6-1</i> and <i>MapaAGL6-2</i>, were isolated from <i>M. patungensis</i>. Sequence alignment and phylogenetic analyses grouped both genes into the <i>AGL6</i> lineage. <i>MapaAGL6-1</i> is expressed only in the perianth whorls, while <i>MapaAGL6-2</i> is strongly expressed in the perianth whorls but is lowly expressed in gynoecium. Furthermore, ectopic expression of <i>MapaAGL6-1</i> results in strong complementation phenotypes in the <i>Arabidopsis</i> <i>ap1</i>-10 flower and production of normal floral organs in four floral whorls only with the petal number reduced in whorl 2, while ectopic expression of <i>MapaAGL6-2</i> only results in petals partly rescued but failing to terminate carpelloid development in <i>Arabidopsis</i> <i>ap1</i>-10 mutant. In addition, the daughter lines generated from a cross between <i>35S</i>::<i>MapaAGL6-1</i> transgenic plants showing strong phenotypes and <i>35S</i>::<i>MapaAGL6-2</i> transgenic plants showing phenotypic changes produce normal flowers. Our results suggest that <i>MapaAGL6-1</i> is a reasonable A-function gene controlling perianth identity in Magnoliaceae, which infers from its expression region and complementation phenotypes in <i>Arabidopsis</i> <i>ap1</i> mutant, while <i>MapaAGL6-2</i> is mainly involved in petaloid tepal development. Our data also provide a new clue to uncover the perianth development and early evolution in basal angiosperms.