Dynamic Replacement of H2A.Z in Chromatin by SWR1 Regulates the Magnitude of Hormone-Responsive Gene Expression in Arabidopsis thaliana Open Access
Zhang, Jingwen (Spring 2026)
Abstract
Chromatin structure plays a critical role in regulating gene expression by controlling DNA accessibility. The structure of chromatin is modified through mechanisms such as the incorporation of histone variants, including H2A.Z, which is involved in transcriptional regulation and environmental responses. Traditionally, H2A.Z has been viewed as a relatively static regulatory chromatin component that is removed upon transcriptional activation. However, recent evidence suggests that H2A.Z is dynamically replaced by the chromatin-remodeling complex SWR1 and maintained during active transcription. This study investigates the functional significance of H2A.Z retention during abscisic acid (ABA) induced stress responses in Arabidopsis thaliana by disrupting the SWR1 chromatin-remodeling complex subunit ARP6, which is required for H2A.Z incorporation. Using estradiol-inducible ARP6 miRNA knockdown lines, the expression of the ABA-responsive gene COR15A was measured at 0, 2, 4, and 6 hours following ABA treatment. While control plants exhibit the expected level of transcriptional response with peak expression at 2 hours, ARP6 knockdown plants maintain the same temporal pattern but show a consistent reduction in the expression magnitude across all time points. These results indicate that ARP6 is not required for transcriptional initiation but is necessary for achieving full transcriptional output. The sustained decrease in gene expression at 4 and 6 hours after ABA treatment further suggests that H2A.Z requires continuous deposition by SWR1 to promote and maintain transcriptional response to stress. Together, these findings challenge the traditional view of H2A.Z as solely repressive and support a model in which H2A.Z plays a dynamic role in regulating the magnitude of transcriptional responses.
Table of Contents
INTRODUCTION 1
RESULTS 5
Validation of Estradiol-Inducible ARP6 Knockdown Lines 5
Figure 1: Validation of estradiol-inducible ARP6 knockdown in third-generation plants 7
Figure 2: Reduction of ARP6 transcript levels in fourth-generation homozygous plants following estradiol treatment 7
ARP6 Knockdown Alters ABA-Induced COR15A Expression 8
Figure 3: ARP6 knockdown reduces ABA-induced COR15A expression 10
Level of COR15A Expression in the Absence of ABA Treatment 11
Figure 4: Effect of ARP6 knockdown on COR15A expression in the absence of ABA treatment 12
DISCUSSION 13
METHODS 17
Plant Sample Preparation 18
Screening of Homozygous ARP6 Knockdown Lines 18
Estradiol and Abscisic Acid Treatment to Homozygous Estradiol-Inducible ARP6 miRNA Lines 19
Western Blotting 20
RNA Extraction 21
Quantitative PCR 21
Statistics 21
REFERENCES 22
APPENDIX 26
Appendix A. Statistical Analysis of COR15A Expression 26
A1. Two-way ANOVA Results for Line 1 26
A2. Post-hoc Comparisons for Line 1 26
A3. Two-way ANOVA Results for Line 5 27
A4. Post-hoc Comparisons for Line 5 27
About this Honors Thesis
| School | |
|---|---|
| Department | |
| Degree | |
| Submission | |
| Language |
|
| Research Field | |
| Keyword | |
| Committee Chair / Thesis Advisor | |
| Committee Members |
Primary PDF
| Thumbnail | Title | Date Uploaded | Actions |
|---|---|---|---|
|
|
Dynamic Replacement of H2A.Z in Chromatin by SWR1 Regulates the Magnitude of Hormone-Responsive Gene Expression in Arabidopsis thaliana () | 2026-04-08 11:51:21 -0400 |
|
Supplemental Files
| Thumbnail | Title | Date Uploaded | Actions |
|---|