C- and D-class MADS-Box Genes from Phalaenopsis equestris (Orchidaceae) Display Functions in Gynostemium and Ovule Development

Abstract

Gynostemium and ovule development in orchid are unique developmental processes in the plant kingdom. Characterization of C- and D-class MADS-box genes could help reveal the molecular mechanisms underlying gynostemium and ovule development in orchids. In this study, we isolated and characterized a C- and a D-class gene, PeMADS1 and PeMADS7, respectively, from Phalaenopsis equestris. These two genes showed parallel spatial and temporal expression profiles, which suggests their cooperation in gynostemium and ovule development. Furthermore, only PeMADS1 was ectopically expressed in the petals of the gylp (gynostemium-like petal) mutant, whose petals were transformed into gynostemium-like structures. Protein-protein interaction analyses revealed that neither PeMADS1 and PeMADS7 could form a homodimer or a heterodimer. An E-class protein was needed to bridge the interaction between these two proteins. A complementation test revealed that PeMADS1 could rescue the phenotype of the AG mutant. Overexpression of PeMADS7 in Arabidopsis caused typical phenotypes of the D-class gene family. Together, these results indicated that both C-class PeMADS1 and D-class PeMADS7 play important roles in orchid gynostemium and ovule development.

An AGAMOUS-like factor is associated with the origin of two domesticated varieties in Cymbidium sinense (Orchidaceae)

“…5). We neither detected any signal of CsAG1 in the floral meristem, nor in the early flower developmental stages, different from the expression of an Orchid AG2 sub-clade member PeMADS1 in Phalaenopsis equestris , which is abundant in the whole floral meristem 26 . Future work using in situ hybridization assays will allow a precise examination of the expression patterns of different AG -like factors, leading to a better understanding under subfunctionalization among these different paralogues.…”

“…Several AG lineage factors have been isolated from Orchidaceae species 21–26 . In Dendrobium crumenatum , the putative C function gene DcOAG1 is highly expressed in all the floral organs, which leads to ap2 -like phenotypes when ectopically expressed in Arabidopsis 23 .…”

“…In the multitepal mutant, whose column has been centripetally replaced by numerous tepal-like structures, the normal expression of CeMADS1 rather than CeMADS2 is disrupted 24 . Interestingly, in the gylp mutant from Phalaenopsis equestris , whose two inner tepals change into gynostemium-like structures, an AG lineage gene, PeMADS1 , is ectopically expressed in the gynostemium-like tepals 26 . All these findings give a strong indication that defects in AG-like factors would have occurred in the origin of the stamenoid-tepal and multi-tepal varieties in C. sinense .…”

Double flower formation in Tricyrtis macranthopsis is related to low expression of AGAMOUS ortholog gene

“…5). The early flowering phenotypes of 35S::TrimAG transgenic Arabidopsis plants are similar to those observed in transgenic plants that ectopically express AGAMOUS ortholog genes (Tzeng et al, 2002;Benedito et al, 2004;Chiang et al, 2009;Hsu et al, 2010;Deng et al, 2011;Chen et al, 2012). These results support the prediction that C-class functional genes should have similar effects on floral induction when ectopically expressed in Arabidopsis (Tzeng et al, 2002), and confirm that TrimAG from T. macranthopsis belongs to the C-class genes.…”

“…2). TrimAG contains a MADS domain, a K-domain, and the C-terminal; the presence of these specific conserved motifs in the TrimAG protein confirmed that TrimAG is an AG ortholog (Rosin et al, 2003;Benedito et al, 2004;Tani et al, 2009;Chen et al, 2012;Delgado Sandoval et al, 2012;Waters et al, 2013).…”