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Abstract
The Arp2/3 complex is an actin nucleator shown to be required throughout plant morphogenesis, contributing to processes such as cell expansion, tissue differentiation or cell wall assembly. A recent publication demonstrated that plants lacking functional Arp2/3 complex also present defects in auxin distribution and transport. This work shows that Arp2/3 complex subunits are predominantly expressed in the provasculature, although other plant tissues also show promoter activity (e.g., cotyledons, apical meristems, or root tip). Moreover, auxin can trigger subunit expression, indicating a role of this phytohormone in mediating the complex activity. Further investigation of the functional interaction between Arp2/3 complex and auxin signaling also reveals their cooperation in determining pavement cell shape, presumably through the role of Arp2/3 complex in the correct auxin carrier trafficking. Young seedlings of arpc5 mutants show increased auxin-triggered proteasomal degradation of DII-VENUS and altered PIN3 distribution, with higher levels of the protein in the vacuole. Closer observation of vacuolar morphology revealed the presence of a more fragmented vacuolar compartment when Arp2/3 function is abolished, hinting a generalized role of Arp2/3 complex in endomembrane function and protein trafficking.
Highlights
The Arp2/3 complex is a conserved actin nucleator consisting of two actin-related proteins (ARP2 and ARP3) and five other complex-specific subunits (ARPC1 to ARPC5) (Welch et al, 1997)
Arp2/3 Complex Subunits Are Expressed in Developing Tissues, Epidermal Cells and Vascular Tissues
In order to pinpoint specific tissues where the Arp2/3 complex has a relevant role, we analyzed the activity of the promoter of several of its subunits fused to GUS at several developmental stages
Summary
The Arp2/3 complex is a conserved actin nucleator consisting of two actin-related proteins (ARP2 and ARP3) and five other complex-specific subunits (ARPC1 to ARPC5) (Welch et al, 1997). Its mutation has been shown to affect the development of complex cell shapes such as trichomes and pavement cells (Le et al, 2003, 2006; Mathur et al, 2003a,b; Schwab et al, 2003; Saedler et al, 2004; Djakovic et al, 2006). Whereas the role of Arp2/3 complex in trichome shape development is the polarization of actin filaments for proper cell wall building (Yanagisawa et al, 2015), the role of Arp2/3 complex in pavement cell shape determination is not fully understood. Previous analysis has shown expression of ARP2 in all plant tissues with predominant expression in vascular tissues (Klahre and Chua, 1999). Little is known about the expression of the other subunits and which factors affect it.
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