Investigation of the role of class I KNOX genes in the floral development of Eschscholzia californica

Four class I KNOX genes were isolated from the Eschscholzia californica, Papaveraceae. Phylogenetic analysis suggests that these four KNOX genes cover all three for the model Arabidopsis thaliana established clades of class I KNOX genes, STM (SHOOT APICAL MERISTEM-LESS), KNAT1/BP (Knotted-like Arabidopsis thaliana-1/BREVIPEDICELLUS) and KNAT2/6 (Knotted-like Arabidopsis thaliana-2/6). Two of these genes (EcSTM1 and EcSTM2) were identified as STM-like genes. Expression analysis in vegetative and floral shoots tips revealed a continuous expression of EcSTM1, EcKNAT1 and EcKNAT2, whereas EcSTM2 is exclusively expressed in early floral buds. EcSTM1-VIGS (Virus-induced gene silencing) resulted in the absence of the inner floral whorls. In flowers of EcSTM2-VIGS treated plants, the carpels were initiated but did not develop properly. Rarely, a floral reversion was observed. Combined silencing of EcSTM1 and EcSTM2 led to combinations of the phenotypes observed for EcSTM1-VIGS and EcSTM2-VIGS.