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Plant cell walls undergo dynamic structural and chemical changes during plant development and growth. Floral organ abscission and lateral root emergence are both accompanied by cell-wall remodeling, which involves the INFLORESCENCE DEFICIENT IN ABSCISSION (IDA)-derived peptide and its receptors, HAESA (HAE) and HAESA-LIKE2 (HSL2). Plant cell walls also act as barriers against pathogenic invaders. Thus, the cell-wall remodeling during plant development could have an influence on plant resistance to phytopathogens. Here, we identified IDA-like 6 (IDL6), a gene that is prominently expressed in Arabidopsis leaves. IDL6 expression in Arabidopsis leaves is significantly upregulated when the plant is suffering from attacks of the bacterial Pseudomonas syringae pv. tomato (Pst) DC3000. IDL6 overexpression and knockdown lines respectively decrease and increase the Arabidopsis resistance to Pst DC3000, indicating that the gene promotes the Arabidopsis susceptibility to Pst DC3000. Moreover, IDL6 promotes the expression of a polygalacturonase (PG) gene, ADPG2, and increases PG activity in Arabidopsis leaves, which in turn reduces leaf pectin content and leaf robustness. ADPG2 overexpression restrains Arabidopsis resistance to Pst DC3000, whereas ADPG2 loss-of-function mutants increase the resistance to the bacterium. Pst DC3000 infection elevates the ADPG2 expression partially through HAE and HSL2. Taken together, our results suggest that IDL6-HAE/HSL2 facilitates the ingress of Pst DC3000 by promoting pectin degradation in Arabidopsis leaves, and Pst DC3000 might enhance its infection by manipulating the IDL6-HAE/HSL2-ADPG2 signaling pathway.

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Ferrous iron/peroxymonosulfate (Fe(II)/PMS) oxidation was employed as a pretreatment method for ultrafiltration process to control membrane fouling caused by natural organic matter, including humic acid (HA), sodium alginate (SA), bovine serum albumin (BSA), and their mixture (HA-SA-BSA). To evaluate the mechanism of fouling mitigation, the effects of Fe(II)/PMS pretreatment on the characteristics of feed water were examined. The degradation of atrazine (ATZ) was also investigated and the species of generated radicals were preliminarily determined. Under the test exposure (15 and 50 μM), Fe(II)/PMS pretreatment effectively mitigated membrane fouling caused by HA, SA and HA-SA-BSA mixture, and the performance improved with the increase of Fe(II) or PMS dose; whereas aggravated BSA fouling at lower doses and fouling alleviation was observed only at a higher dose (50/50 μΜ). The fouling mitigation was mainly attributed to the effective reduction of organic loadings by coagulation with in-situ formed Fe(III). Its performance was comparable or even slightly higher than single coagulation with Fe(III), most likely due to the oxidation by Fe(II)/PMS process. Fe(II)/PMS oxidation showed better performance in reducing DOC and UV, fluorescence intensities of fluorescent components and UV-absorbing compounds than single coagulation. In addition, Fe(II)/PMS pretreatment was efficient in ATZ degradation due to the generation of sulfate and hydroxyl radicals, whereas coagulation was ineffective to remove it.