Analysis of B function in legumes: PISTILLATA proteins do not require the PI motif for floral organ development in Medicago truncatula.
The B-class gene PISTILLATA (PI) codes for a MADS-box transcription factor required for floral organ identity in angiosperms. Unlike Arabidopsis, it has been suggested that legume PI genes contribute to a variety of processes, such as the development of floral organs, floral common petal-stamen primordia, complex leaves and N-fixing root nodules. Another interesting feature of legume PI homologues is that some of them lack the highly conserved C-terminal PI motif suggested to be crucial for function. Therefore, legume PI genes are useful for addressing controversial questions on the evolution of B-class gene function, including how they may have diverged in both function and structure to affect different developmental processes. However, functional analysis of legume PI genes has been hampered because no mutation in any B-class gene has been identified in legumes. Here we fill this gap by studying the PI function in the model legume species Medicago truncatula using mutant and RNAi approaches. Like other legume species, M. truncatula has two PI homologues. The expression of the two genes, MtPI and MtNGL9, has strongly diverged, suggesting differences in function. Our analyses show that these genes are required for petal and stamen identity, where MtPI appears to play a predominant role. However, they appear not to be required for development of the nodule, the common primordia or the complex leaf. Moreover, both M. truncatula PI homologues lack the PI motif, which indicates that the C-terminal motif is not essential for PI activity.
Benlloch
Reyes
R
Instituto de Biología Molecular y Celular de Plantas (IBMCP), UPV-CSIC., 46022 Valencia, Spain.
Roque
Edelín
E
Ferrándiz
Cristina
C
Cosson
Viviane
V
Caballero
Teresa
T
Penmetsa
Ramachandra V
RV
Beltrán
José Pío
JP
Cañas
Luís Antonio
LA
Ratet
Pascal
P
Madueño
Francisco
F
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D018744:DNA, Plant / Q000235:genetics; D035264:Flowers / Q000235:genetics / Q000254:growth & development*; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D026161:MADS Domain Proteins / Q000235:genetics / Q000378:metabolism*; D046913:Medicago truncatula / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D009154:Mutation; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D034622:RNA Interference; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
D018744:DNA, Plant; D026161:MADS Domain Proteins; D010940:Plant Proteins