Regulation of multiple developmental processes by AtFH1 and AtARP3 mediated actin cytoskeleton in Arabidopsis thaliana
The actin cytoskeleton plays a multifaceted role in plant biology. It is involved in several developmental processes and is needed to cope with both biotic and abiotic stresses. Actin is a highly conserved, the most abundant and multifunctional globular protein that can exist either as a globular sub-unit (G-actin) or filamentous (F-actin) form. F-actin is the microfilament part of the cytoskeleton polymerized from G-actin. Actin cytoskeleton polymerization is facilitated by several proteins like formins (polymerizing linear actin cytoskeletons) and the ARP2/3 complex (polymerizing branched actin cytoskeletons). AtFH1 and AtARP3 are important regulators of actin cytoskeleton in Arabidopsis thaliana and belong to the formins and ARP2/3 complex, respectively. The effect of AtFH1 and AtARP3 on actin cytoskeleton reorganization and its subsequent regulation on multiple developmental processes in Arabidopsis thaliana were studied using both single and double mutants of these genes. Simultaneous mutation of AtFH1 and AtARP3 appears to have a lethal effect. Although fh1-1 was not a true knockout mutant, the double mutant fh1-1/arp3-1 further recovered some expression of the AtFH1 gene compared to fh1-1 single mutant but a homozygous double mutant was not obtained. This double mutant showed several unique characteristics compared to the wild type and each single mutant, such as small plants with short, narrow and pale green leaves; short root, slow root growth rate; greater gravitropic response; altered lateral root locations etc. At the cellular level, the double mutant exhibited deformities in epidermal cell circularity; short root hairs; distinct trichome phenotype; small mesophyll cells with lower chloroplasts content; small pollen size, a number of which were structurally distorted. The double mutant produced tiny flowers with distinct floral organ structures that vastly affected the fertility resulted a short silique and a smaller number of seeds due to aborted ovule or embryo. Most of these characteristics were absent in the single mutants, fh1-1 and arp3- 1, and/or were not as severe as in the double mutant. The aberrant actin cytoskeleton organizations that were distinctive in each mutant were observed in epidermal pavement cells, trichome cells and mesophyll cells. So, AtFH1 and AtARP3 appears to regulate several biological processes in Arabidopsis thaliana by maintaining the proper organization of actin cytoskeleton.
AtFH1, AtARP3, Actin cytoskeleton
Master of Science (M.Sc.)