Disease relevance of ACT1

• ADF increases the rate of propulsion of Listeria monocytogenes in highly diluted, ADF-limited platelet extracts and shortens the actin tails [1].
• Some of them are involved either in the imbibition process of the seeds (such as an actin isoform or a WD-40 repeat protein) or in the seed dehydration process (e.g. cytosolic glyceraldehyde-3-phosphate dehydrogenase) [2].
• The actin cytoskeleton and the microtubule system of the cells, as well as the dynamics of root growth, remain unchanged after short-term application of NR, indicating a relatively low toxicity of this chemical [3].

High impact information on ACT1

• In addition, actin-dependent relocalization of PIN3 in response to gravity provides a mechanism for redirecting auxin flux to trigger asymmetric growth [4].
• A major property of ADF is its ability to enhance the in vitro turnover rate (treadmilling) of actin filaments to a value comparable to that observed in vivo in motile lamellipodia [1].
• Plasma membrane and intracellular pools of AUX1 are interconnected by actin-dependent constitutive trafficking, which is not sensitive to the vesicle trafficking inhibitor brefeldin A [5].
• Immunolabeling of callus tissue with actin subclass-specific antibodies revealed that the predominant ACT7 is coexpressed with the other actin proteins [6].
• In contrast, reduced AtADF expression promoted the formation of actin cables, resulted in a delay in flowering, and stimulated cell expansion as well as organ growth [7].

Biological context of ACT1

• Comparison of the 5' flanking regions of ACT1 and ACT3 revealed a number of short conserved sequences, which may direct their common transcriptional and post-transcriptional regulation [8].
• ACT1 reporter gene constructs were strongly expressed in both pollen and ovules of tobacco and in the pollen of rice [9].
• The conservation of their expression pattern and amino acid sequences suggests that this actin subclass plays a distinct and required role in the plant cytoskeleton [8].
• The actin cytoskeleton dynamically reorganizes the cytoplasm during cell morphogenesis [10].
• Actin filaments comprise an essential cytoskeletal array that organizes the cytoplasm during growth and cell division [11].

Anatomical context of ACT1

• This model was reinforced by genetic studies in the Drosophila central nervous system and Dictyostelium, where the knockout of certain SCAR-complex components leads to excessive SCAR-mediated actin polymerization [12].
• Actin filaments position the endomembrane system and act as a substrate on which organelle motility occurs [11].
• PIN3 localizes to the plasma membrane and to vesicles that cycle in an actin-dependent manner [4].
• We suggest that the coexpression, and probably the copolymerization, of the abundant ACT7 with the other actin isovariants in cultured cells may facilitate isovariant dynamics well suited for cellular responses to external stimuli such as hormones [6].
• A similar decrease in NHR was observed following treatment of the wild-type Arabidopsis plants with cytochalasin E, an inhibitor of actin microfilament polymerisation [13].

Associations of ACT1 with chemical compounds

• Latrunculin B (Lat-B) treatment of hypocotyls caused depolymerization of actin MFs in endodermal cells and a significant reduction of hypocotyl growth rates [14].
• Mutants act1 and fad5, which are deficient in C16 unsaturated fatty acids, had wild-type levels of C6-aldehyde production [15].
• A clear difference was observed after ABA treatment, namely, neither stomatal closing nor depolymerization of actin filaments was observed in guard cells of the mutant [16].
• Cortical actin filaments in guard cells respond differently to abscisic acid in wild-type and abi1-1 mutant Arabidopsis [16].
• Unlike mammalian peroxisomes which move on microtubules, plant peroxisome movement is dependent on actin microfilaments and myosin motors, since it is blocked by treatment with latrunculin B and butanedione monoxime, respectively [17].

Other interactions of ACT1

• Comparison of ACT1 and ACT3 cDNA and genomic sequences revealed highly divergent flaking and intron sequences, whereas they encoded nearly identical proteins [8].
• In the wild-type plants, ACT1 is predominantly expressed in the mature pollen, growing pollen tubes, and ovules, whereas ACT2 is constitutively and strongly expressed in all vegetative tissues and organs, but not in pollen [18].
• Transgenic overexpression of the ACT7 vegetative isovariant and ectopic expression of the ACT1 reproductive actin isovariant also rescued the root hair elongation defects of the act2-1 mutant [19].
• Therefore, actin cytoskeletal function and EDS1 activity, in combination, are major contributors to NHR in Arabidopsis against wheat powdery mildew [13].
• Actin depolymerizing factor (ADF) is a key regulator of the organization of the actin cytoskeleton during various cellular activities [20].

Analytical, diagnostic and therapeutic context of ACT1

• Gene-specific RNA gel blot hybridization and reverse transcriptase-polymerase chain reaction analyses demonstrated that the distribution of ACT1 and ACT3 mRNAs was very similar: both preferentially accumulated at high levels in mature pollen and at very low levels in the other major organs [8].
• Localization studies using Alexa Fluor-phalloidin in conjugation with confocal microscopy demonstrated a longitudinally and transversely oriented actin MF network in endodermal cells of stems and hypocotyls [14].

References