Talk abstracts
Talk on Friday 04:00-04:15pm submitted by Anna Hu
The kernel of truth: The role of ASAP complex in abscisic acid response regulation during seed germination and early seedling development in Arabidopsis thaliana
Anna Hu (Biochemistry Program, Department of Biology), Claire Schaef (Biochemistry Program, Department of Biology), Xiao-Ning Zhang (Biochemistry Program, Department of Biology)
Abstract:
In eukaryotes, a series of post-transcriptional events produce diverse gene products. These events are mediated by different RNA-binding proteins (RBP). One such conserved complex of RBPs is the apoptosis-and splicing-associated protein (ASAP) complex. In Arabidopsis thaliana, the ASAP complex is composed of three subunits, SERINE/ARGININE-rich 45 (SR45), apoptotic chromatin condensation inducer in the nucleus (Acinus), and Sin3A associated protein 18 (SAP18). Previously, we found that SR45 is required to maintain a normal level of SAP18 protein in the nucleus. Overexpressing SAP18-GFP in the sr45-1 null mutant caused an increase in the expression of FlOWER LOCUS C (FLC), a suppressor for flowering, and a delay in reproduction initiation (flowering) compared to the non-transgenic sr45-1 mutant, suggesting that the ASAP complex may be involved in the regulation of vegetative-to-reproductive transition. In addition, the sr45-1 mutant exhibits abnormal sensitivity to abscisic acid (ABA), a plant hormone that inhibits seed germination and is important for plant abiotic stress response. To investigate whether the ASAP complex is involved in the regulation of ABA response, the wild-type (Col-0), the sr45-1 mutant, Col-0 overexpressing SAP18-GFP and the sr45-1 mutant overexpressing SAP18-GFP were subjected to either mock or 1 uM ABA treatment. Their germination percentages and hypocotyl growth were assessed. All etiolated seedlings were found to have shorter hypocotyls with ABA treatment. The most dramatic difference was seen in the sr45-1 mutant lines overexpressing SAP18-GFP, where most of the seeds were arrested immediately after the exposure to ABA. This suggests that an abnormal distribution of ASAP component proteins may be a reason for the observed hypersensitivity to ABA. In order to understand how this hypersensitivity was achieved, the expression of genes involved in ABA metabolism, ABA signaling pathways, or ABA response was evaluated using qPCR among different genotypes described above. Future research includes an investigation of ABA sensitivity and the expression of these genes in SAP18 knockdown mutant lines as well.
References:
Chen, S. L., Rooney, T. J., Hu, A. R., Beard, H. S., Garrett, W. M., Mangalath, L. M., . . . Zhang, X.-N. (2019). Quantitative proteomics reveals a role for SERINE/ARGININE-RICH 45 in regulating RNA metabolism and modulating transcriptional suppression via the ASAP complex in Arabidopsis thaliana. Fronteirs in Plant Science.
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Keywords: apoptosis-and splicing-associated protein (ASAP), Arabidopsis thaliana, abscisic acid