BTB and TAZ domain scaffold proteins perform a crucial function in Arabidopsis development.
In Arabidopsis, bric-a-brac, tramtrack and broad (BTB) domain scaffold proteins form a family of 80 proteins that have involvement in various signaling pathways. The five members of the subfamily of BTB AND TAZ DOMAIN proteins (BT1-BT5) have a typical domain structure that is only observed in land plants. Here, we present a functional analysis of the BT family, of which at least four members are encoded by auxin-responsive genes. BT1 is a short-lived protein that is characteristically targeted for degradation by the 26S proteasome. Expression pattern, gene structure and sequence analyses indicate that BT1 and BT2 are closely related. They both localize to the nucleus and the cytosol, whereas the remaining BT proteins were determined as cytosolic proteins. Detailed molecular and phenotypic analysis of plants segregating for null mutations in the BT family revealed substantial redundancy among the BT members, and highlighted that BT proteins perform crucial roles in both male and female gametophyte development. BT2 seems to be the predominant gene in this process, in which it is functionally replaced by BT3 and BT1 through reciprocal transcription regulation. Compensational expression alters the steady-state mRNA levels among the remaining BT family members when other BT members are lost, and this contributes towards functional redundancy. Our data provide a surprising example of functional redundancy among genes required during gametophyte development, something that could not be detected in the current screens for gametophyte mutants.
Robert
Hélène S
HS
Department of Molecular and Developmental Genetics, Institute of Biology, Leiden University, Wassenaarseweg 64, 2333 AL Leiden, The Netherlands.
Quint
Ab
A
Brand
Daan
D
Vivian-Smith
Adam
A
Offringa
Remko
R
D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D003600:Cytosol / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D055993:Germ Cells, Plant / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism; D007178:Inbreeding; D005810:Multigene Family; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010641:Phenotype; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D055550:Protein Stability; D011523:Protoplasts / Q000166:cytology / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D012639:Seeds / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D013045:Species Specificity; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection
D029681:Arabidopsis Proteins; C519868:BT2 protein, Arabidopsis; D046912:Multiprotein Complexes; D012333:RNA, Messenger; D018749:RNA, Plant; D014157:Transcription Factors; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease