Characterization of Antirrhinum Petal Development and Identification of Target Genes of the Class B MADS Box GeneDEFICIENS [W]

Abstract

The class B MADS box transcription factors DEFICIENS (DEF) and GLOBOSA (GLO) of Antirrhinum majus together control the organogenesis of petals and stamens. Toward an understanding of how the downstream molecular mechanisms controlled by DEF contribute to petal organogenesis, we conducted expression profiling experiments using macroarrays comprising >11,600 annotated Antirrhinum unigenes. First, four late petal developmental stages were compared with sepals. More than 500 ESTs were identified that comprise a large number of stage-specifically regulated genes and reveal a highly dynamic transcriptional regulation. For identification of DEF target genes that might be directly controlled by DEF, we took advantage of the temperature-sensitive def-101 mutant. To enhance the sensitivity of the profiling experiments, one petal developmental stage was selected, characterized by increased transcriptome changes that reflect the onset of cell elongation processes replacing cell division processes. Upon reduction of the DEF function, 49 upregulated and 52 downregulated petal target genes were recovered. Eight target genes were further characterized in detail by RT-PCR and in situ studies. Expression of genes responding rapidly toward an altered DEF activity is confined to different petal tissues, demonstrating the complexity of the DEF function regulating diverse basic processes throughout petal morphogenesis.

Divergent Regulatory OsMADS2 Functions Control Size, Shape and Differentiation of the Highly Derived Rice Floret Second-Whorl Organ

“…These observations are interesting in light of the global expression profiling data from Arabidopsis pi and ap3 mutants where the affected downstream genes do not include such a large proportion of cell division genes (Zik and Irish 2003;Wellmer et al 2004). On the other hand 8% of the potential target genes of Antirrhinum DEF are factors affecting cell cycle and DNA processing (Bey et al 2004).…”

Wrinkled petals and stamens 1, is required for the morphogenesis of petals and stamens in Lotus japonicus

“…However, the development of floral organs requires not only the ABC function genes but also the downstream factors to elaborate their final shape. Although many putative targets of the floral organ identity genes were identified using micro-arrays analysis [6,27], robust analysis on their function is few and so far only NAP has been shown to be a direct target of AP3/PI [5].…”

Do Transcription Factors Play Special Roles in Adaptive Variation?

“…In addition, empirical evidence shows that TFs that operate early in a regulatory hierarchy often continue to work controlling processes later in differentiation as well (Stern, 2000;Wray et al, 2003). This can be seen in the operation of some MADS domain proteins in plants, including AP1 that plays a role in determining the induction of the transition to the floral meristem and also in determining floral organ identity (Becker and Theissen, 2003), and the B-function proteins Deficiens and Globosa in Antirrhinum (equivalent to AP1 and PI, respectively, in Arabidopsis) that control later stages of petal and stamen differentiation as well as determining organ identity (Schwarz Sommer et al, 1992;Zachgo et al, 1995;Bey et al, 2004;Lauri et al, 2006). This feature of higher-order TFs adds to their potential for causing pleiotropic effects when misexpressed, but also complicates the possible outcomes of variation in their expression on phenotype.…”