PvALF and FUS3 activate expression from the phaseolin promoter by different mechanisms.
Transcription from the phaseolin (phas) promoter requires two major events: chromatin remodeling, mediated by PvALF, a B3 domain factor, and activation by an ABA-induced signal transduction cascade. Expression from phas is normally seed-specific, but high levels of expression in leaves can be obtained by ectopic expression of PvALF. Here, the system was used to compare the ability of PvALF and Arabidopsis FUS3, another B3 domain transcription factor that lacks the N-terminal activation and B1 domain present in PvALF, to activate phas expression in vegetative tissues. When compared to PvALF-mediated phas activation in the presence of ABA, a delay in phas activation was observed in the presence of both FUS3 and ABA in vegetative tissue. Significant differences in histone modifications at the phas promoter were mediated by FUS3 and PvALF, suggesting that they function through different epigenetic mechanisms. The relationship between PvALF and ABI5, a bZIP transcription factor, in mediating phas expression was also evaluated. Interestingly, over-expression of ABI5 rendered phas expression ABA-independent in the presence of PvALF. Changes in phas activity in different regions within seed embryos were demonstrated using abi5 mutants. Our results show that (1) redundant factors, such as PvALF and FUS3, employ different mechanisms to regulate their common target gene (phas); (2) ABI5, and possibly other redundant bZIP factors, act downstream of ABA in modulating phas expression in the presence of PvALF.
Institute of Developmental and Molecular Biology and Department of Biology, Texas A&M University, College Station, TX 77843-3155, USA.
Danny
D
W-K Ng
Timothy C
TC
Hall
D000040:Abscisic Acid / Q000494:pharmacology; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D050976:Basic-Leucine Zipper Transcription Factors / Q000235:genetics / Q000378:metabolism; D002843:Chromatin / Q000187:drug effects / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005966:Glucuronidase / Q000235:genetics / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D008856:Microscopy, Fluorescence; D009154:Mutation; D010937:Plant Growth Regulators / Q000494:pharmacology; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
C409743:ABI5 protein, Arabidopsis; D029681:Arabidopsis Proteins; D050976:Basic-Leucine Zipper Transcription Factors; D002843:Chromatin; C502726:FUSCA3 protein, Arabidopsis; D006657:Histones; D010937:Plant Growth Regulators; D010940:Plant Proteins; C096083:PvAlf protein, Phaseolus vulgaris; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C048826:phaseolin protein, Phaseolus vulgaris; D049452:Green Fluorescent Proteins; D000040:Abscisic Acid; D005966:Glucuronidase