Ds tagging of BRANCHED FLORETLESS 1 (BFL1) that mediates the transition from spikelet to floret meristem in rice (Oryza sativa L).
BACKGROUND
The genetics of spikelet formation, a feature unique to grasses such as rice and maize, is yet to be fully understood, although a number of meristem and organ identity mutants have been isolated and investigated in Arabidopsis and maize. Using a two-element Ac/Ds transposon tagging system we have isolated a rice mutant, designated branched floretless 1 (bfl1) which is defective in the transition from spikelet meristem to floret meristem.


RESULTS
The bfl1 mutant shows normal differentiation of the primary rachis-branches leading to initial spikelet meristem (bract-like structure equivalent to rudimentary glumes) formation but fails to develop empty glumes and florets. Instead, axillary meristems in the bract-like structure produce sequential alternate branching, thus resulting in a coral shaped morphology of the branches in the developing panicle. The bfl1 mutant harbours a single Ds insertion in the upstream region of the BFL1 gene on chromosome 7 corresponding to PAC clone P0625E02 (GenBank Acc No. message URL http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=nucleotide&list_uids=34395191&dopt=GenBank&term=ap004570AP004570). RT-PCR analyses revealed a drastic reduction of BFL1 transcript levels in the bfl1 mutant compared to that in the wild-type. In each of the normal panicle-bearing progeny plants, from occasional revertant seeds of the vegetatively-propagated mutant plant, Ds was shown to be excised from the bfl1 locus. BFL1 contains an EREBP/AP2 domain and is most likely an ortholog of the maize transcription factor gene BRANCHED SILKLESS1 (BD1).


CONCLUSIONS
bfl1 is a Ds-tagged rice mutant defective in the transition from spikelet meristem (SM) to floret meristem (FM). BFL1 is most probably a rice ortholog of the maize ERF (EREBP/AP2) transcription factor gene BD1. Based on the similarities in mutant phenotypes bfl1 is likely to be an allele of the previously reported frizzy panicle locus.
D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D015139:Blotting, Southern; D004251:DNA Transposable Elements / Q000235:genetics*; D018744:DNA, Plant / Q000235:genetics; D035264:Flowers / Q000235:genetics* / Q000254:growth & development / Q000648:ultrastructure; D018506:Gene Expression Regulation, Plant; D018745:Genome, Plant; D005838:Genotype; D018519:Meristem / Q000235:genetics* / Q000254:growth & development / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D016254:Mutagenesis, Insertional; D009154:Mutation; D012275:Oryza / Q000235:genetics* / Q000254:growth & development; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics
D004251:DNA Transposable Elements; D018744:DNA, Plant; D010940:Plant Proteins; D018749:RNA, Plant; D014157:Transcription Factors