Abstract
The actin cytoskeleton participates in numerous cellular processes, including less-characterized processes, such as nuclear organization, chromatin remodeling, transcription, and signal transduction. As a key regulator of actin cytoskeletal dynamics, the actin related protein 2/3 complex (Arp2/3 complex) controls multiple developmental processes in a variety of tissues and cell types. To date, the role of the Arp2/3 complex in plant disease resistance signaling is largely unknown. Herein, we identified and characterized wheat ARPC3, TaARPC3, which encodes the C3 subunit of the Arp2/3 complex. Expression of TaARPC3 in the arc18 mutant of Saccharomyces cerevisiae Δarc18 resulted in complementation of stress-induced phenotypes in S. cerevisiae, as well as restore wild-type cell shape malformations. TaARPC3 was found predominantly to be localized in the nucleus and cytoplasm when expressed transiently in wheat protoplast. TaARPC3 was significantly induced in response to avirulent race of Puccinia striiformis f. sp. tritici (Pst). Knock-down of TaARPC3 by virus-induced gene silencing resulted in a reduction of resistance against Pst through a specific reduction in actin cytoskeletal organization. Interestingly, this reduction was found to coincide with a block in reactive oxygen species (ROS) accumulation, the hypersensitive response (HR), an increase in TaCAT1 mRNA accumulation, and the growth of Pst. Taken together, these findings suggest that TaARPC3 is a key subunit of the Arp2/3 complex which is required for wheat resistance against Pst, a process that is associated with the regulation of the actin cytoskeleton.
Highlights
The plant actin cytoskeleton forms a contiguous network within all eukaryotic cells and is associated with the function of many cellular processes, such as cell division and development, cell polarity, and organelle movement (Kim et al, 2005; Sparkes et al, 2009; Yokota et al, 2009)
These results indicate that TaARPC3 (Genbank accession number KU746328) is a typical member of the actin-related protein 2/3 (Arp2/3) complex in wheat
We isolated the wheat TaARPC3 gene, with duplication across the chromosomes 7A, 7B, and 7D, which has a similar conserved P21-Arc domain to that found in numerous other ARPC3 proteins from a wide variety of monocotyledonous plants
Summary
The plant actin cytoskeleton forms a contiguous network within all eukaryotic cells and is associated with the function of many cellular processes, such as cell division and development, cell polarity, and organelle movement (Kim et al, 2005; Sparkes et al, 2009; Yokota et al, 2009). During cell growth and development, as well as mechano-stimulation and in response to stress, the actin array undergoes rapid and highly regulated changes (Shimada et al, 2006; Hardham et al, 2007, 2008; Li et al, 2014). Plenty of studies have demonstrated that the actin cytoskeleton acts a pivotal part in plant basic defensive reaction and non-host resistance to various pathogens (Kobayashi et al, 1994; Hardham et al, 2007; Tian et al, 2009). The microfilament cytoskeleton participated in race-specific resistance; for example, previous work demonstrated that AtADF4 mediates effector-triggered immunity (ETI) signaling through recognition of signaling activated in response to the recognition of the Pseudomonas effector AvrPphB (Tian et al, 2009)
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