Abstract
Transcriptional regulations are involved in many aspects of plant development and are mainly achieved through the actions of transcription factors (TF). To investigate the mechanisms of plant development, we carried out genetic screens for mutants with abnormal shoot development. Taking an activation tagging approach, we isolated a gain-of-function mutant abs2-1D (abnormal shoot 2-1D). abs2-1D showed pleiotropic growth defects at both the vegetative and reproductive developmental stages. We cloned ABS2 and it encodes a RAV sub-family of plant B3 type of transcriptional factors. Phylogenetic analysis showed that ABS2 was closely related to NGATHA (NGA) genes that are involved in flower development and was previously named NGATHA-Like 1 (NGAL1). NGAL1 was expressed mainly in the root and the filament of the stamen in flower tissues and sub-cellular localization assay revealed that NGAL1 accumulated in the nucleus. Interestingly, over-expression of NGAL1 driven by the constitutive 35S promoter led to transgenic plants with conspicuous flower defects, particularly a loss-of-petal phenotype. A loss-of-function ngal1-1 mutant did not show obvious phenotype, suggesting the existence of redundant activities and also the utility of gain-of-function genetic screens. Our results show that the over-expression of NGAL1 is capable of altering flower petal development, as well as shoot development.
Highlights
In eukaryotic organisms, gene expression regulations can occur at multiple levels to ensure the proper elaboration of the information stored in the genetic materials
The Identification of abnormal shoot2-1D (abs2-1D) Mutant In our previous work looking for genetic suppressors of the Arabidopsis yellow variegated mutant, we carried out var2 activation tagging mutagenesis [19]
In our large-scale screens for var2 suppressors, we identified a series of dominant mutants with altered shoot development that we named abs mutants [20]
Summary
Gene expression regulations can occur at multiple levels to ensure the proper elaboration of the information stored in the genetic materials. Considering the central roles they play, it is not surprising to see the presence of large numbers of TFs in eukaryotic genomes. The model plant Arabidopsis thaliana genome contains more than 1500 transcription factors, accounting for ,6% of its estimated ,27,000 genes genome [2]. TFs contain distinct types of DNA-binding domains and transcriptional regulation regions and are capable of activating or repressing the expressions of a large number of target genes [3,4,5,6]. One family of transcription factors that has been under extensive investigation in plants is the plant-specific B3 superfamily TFs, which contain a characteristic ,110 amino acids B3 domain responsible for DNA binding [7]. Arabidopsis B3 family of TFs can be further grouped into four subfamilies: ARF (AUXIN RESPONSE FACTOR), LAV
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