## 2 Results
### Ab-FAR-1 Asp and AtADF3 Are Involved in the PTI of Arabidopsis thaliana  
The bacterial flagellin or its \(N\)-terminal peptide mimics (Flg22), as a microbe associated molecular pattern, could be recognized by the host's FLAGELLIN-SENSING2 (FLS2) to further activate a basal resistance response PTI [45]. Hallmarks of PTI include cytosolic acidification, changes in cytoplasmic streaming patterns, rapid generation of reactive oxygen species (ROS), callose deposition, and enhanced phospholipid turnover as well as activation of mitogen-activated protein kinase (MAPK) and calcium-dependent protein kinase (CDPK) phosphorylation cascades [46]. To investigate the effects of Ab-FAR-1 and AtADF3 on plant PTI, we tested the callose deposition, ROS production, and defence gene expression levels induced by flg22. Compared with WT _A. thaliana_, callose deposition (\(p<0.01\)) and ROS production (\(p<0.05\)) were both significantly decreased in the leaves of _A. thaliana_ overexpressing Ab-FAR-1 Asp (FOE1) and _adf3_ mutants following flg22 treatment (Figure 10a-d). The MAPK pathway marker genes (_FRK1_, _CYP81_, and _WRKY33_) and CDPK pathway marker genes (_NHL10_ and _PHII_) in flg22-mediated PTI of these plants were monitored using RT-qPCR (Figure 10e). The expression levels of _FRKI_, _CYP81_, _NHL10_, and _PHII_ in FOE1 and _NHL10_ and _PHII_ in the _adf3_ mutant were significantly down-regulated (\(p<0.05\)) compared with those in WT _A. thaliana_. These results suggest that Ab-FAR-1 Asp and AtADF3 are both involved in the MAPK and CDPK pathways of plant immunity, and they might have overlapping functions, which indicates that Ab-FAR-1 Asp might further suppress _A. thaliana_ PTI through AtADF3. Figure 8: Ab-FAR-1 Asp can inhibit AtADF3-mediated F-actin depolymerizing function. **(a)** Over-expression of Ab-FAR-1 Asp was not affected by the transcription level of AtADF3. **(b)** The F-actin depolymerizing activities of AtADF3 were determined using high-speed co-sedimentation assays; F-actin filaments were incubated with different treatments (CK, T1-T3). The pellet and supernatant fractions were analysed by SDS-PAGE. CK, 4 uM F-actin alone; T1, 6 uM rAtADF3/ 4 uM F-actin; T2, 6 uM BSA/6 uM rAtADF3/4 uM F-actin; T3, 6 uM rAb-FAR-1/6 uM rAtADF3/4 uM F-actin. **(c)** Direct visualization of F-actin in pellet by Alexa-488-phalloidin staining method. Bar = 20 uM. **(d)** The content of actin was quantified by fluorescence intensity. There were three independent biological replicates. Different letters above bars denote values that are significantly different from each other (\(p<0.05\), Tukey’s test). Figure 10: Callose deposition and ROS production was suppressed in leaves of _Arabidopsis thaliana_ overexpressing Ab-FAR-1 and _adf3_ mutant following fig22 treatment. **(a,b)** The callose deposition was suppressed in leaves of _A. thaliana_ overexpressing Ab-FAR-1 and _adf3_ mutant following fig22 treatment. Bar=200 \(\upmu\)m. Values are presented as the means \(\pm\) SE, \(n=15\). **(c,d)** The ROS production was suppressed in leaves of _A. thaliana_ overexpressing Ab-FAR-1 and _adf3_ mutant following fig22 treatment. Values are presented as the means \(\pm\) SE, \(n=15\). **(e)** The _A. thaliana_ expressing Ab-FAR-1 and _adf3_ mutant suppresses the expression of defence genes in _A. thaliana_. The _UBP22_ was a reference gene. WT, wild-type Col-0 ecotype _A. thaliana_; FOE1, Ab-FAR-1 overexpression _A. thaliana_ line 1#; _adf3_, _A. thaliana_ AtADF3 mutant. Values are presented as the means \(\pm\) SE, \(n=3\). Asterisks indicate values that are significantly different (**\(p<0.05\), **\(p<0.01\); \(t\)-test) from the WT. Figure 9: Effect of Ab-FAR-1 on actin cytoskeleton. The actin cytoskeleton (green) of leaf epidermis **(a,b)** and hypocotyl **(c,d)** in wild-type and Ab-FAR-1 transgenic wild-type _Arabidopsis thaliana_ seedlings.. Latrunculin B-treated leaf epidermis **(e,f)** and hypocotyl cells **(g,h)** of wild-type and Ab-FAR-1 transgenic _A. thaliana_ seedlings.