Search

Heterostructures of two‐dimensional materials realise novel and enhanced physical phenomena, making them attractive research targets. Compared to inorganic materials, coordination nanosheets have virtually infinite combinations, leading to tunability of physical properties and are promising candidates for heterostructure fabrication. Although stacking of coordination materials into vertical heterostructures is widely reported, reports of lateral coordination material heterostructures are few. Here we show the successful fabrication of a seamless lateral heterojunction showing diode behaviour, by sequential and spatially limited immersion of a new metalladithiolene coordination nanosheet, Zn3BHT, into aqueous Cu(II) and Fe(II) solutions. Upon immersion, the Zn centres in insulating Zn3BHT are replaced by Cu or Fe ions, resulting in conductivity. The transmetallation is spatially confined, occurring only within the immersed area. We anticipate that our results will be a starting point towards exploring transmetallation of various two‐dimensional materials to produce lateral heterojunctions, by providing a new and facile synthetic route. [ABSTRACT FROM AUTHOR]

Phytoplasmas are insect-transmitted plant pathogens that cause substantial losses in agriculture. In addition to economic impact, phytoplasmas induce distinct disease symptoms in infected plants, thus attracting attention for research on molecular plant-microbe interactions and plant developmental processes. Due to the difficulty of establishing an axenic culture of these bacteria, culture-independent genome characterization is a crucial tool for phytoplasma research. However, phytoplasma genomes have strong nucleotide composition biases and are repetitive, which make it challenging to produce complete assemblies. In this study, we utilized Illumina and Oxford Nanopore sequencing technologies to obtain the complete genome sequence of ' Candidatus Phytoplasma luffae' strain NCHU2019 that is associated with witches' broom disease of loofah (Luffa aegyptiaca) in Taiwan. The fully assembled circular chromosome is 769 kb in size and is the first representative genome sequence of group 16SrVIII phytoplasmas. Comparative analysis with other phytoplasmas revealed that NCHU2019 has a remarkably repetitive genome, possessing a pair of 75 kb repeats and at least 13 potential mobile units (PMUs) that account for ∼25% of its chromosome. This level of genome repetitiveness is exceptional for bacteria, particularly among obligate pathogens with reduced genomes. Our genus-level analysis of PMUs demonstrated that these phytoplasma-specific mobile genetic elements can be classified into three major types that differ in gene organization and phylogenetic distribution. Notably, PMU abundance explains nearly 80% of the variance in phytoplasma genome sizes, a finding that provides a quantitative estimate for the importance of PMUs in phytoplasma genome variability. Finally, our investigation found that in addition to horizontal gene transfer, PMUs also contribute to intra-genomic duplications of effector genes, which may provide redundancy for subfunctionalization or neofunctionalization. Taken together, this work improves the taxon sampling for phytoplasma genome research and provides novel information regarding the roles of mobile genetic elements in phytoplasma evolution. [ABSTRACT FROM AUTHOR]

Phytoplasmas are uncultivated plant-pathogenic bacteria with agricultural importance. Those belonging to the 16SrII group, represented by ' Candidatus P. aurantifolia', have a wide range of plant hosts and cause significant yield losses in valuable crops, such as pear, sweet potato, peanut, and soybean. In this study, a method that combines immunoprecipitation-based enrichment and MinION long-read DNA sequencing was developed to solve the challenge of phytoplasma genome studies. This approach produced long reads with high mapping rates and high genomic coverage that can be combined with Illumina reads to produce complete genome assemblies with high accuracy. We applied this method to strain NCHU2014 and determined its complete genome sequence, which consists of one circular chromosome with 635,584 bp and one plasmid with 4,224 bp. Although ' Ca. P. aurantifolia' NCHU2014 has a small chromosome with only 471 protein-coding genes, it contains 33 transporter genes and 27 putative effector genes, which may contribute to obtaining nutrients from hosts and manipulating host developments for their survival and multiplication. Two effectors, the homologs of SAP11 and SAP54/PHYL1 identified in ' Ca. P. aurantifolia' NCHU2014, have the biochemical activities in destabilizing host transcription factors, which can explain the disease symptoms observed in infected plants. Taken together, this study provides the first complete genome available for the 16SrII phytoplasmas and contributes to the understanding of phytoplasma pathogenicity. [ABSTRACT FROM AUTHOR]

In an article published in Angewandte Chemie International Edition, Hiroshi Nishihara et al. present a new method for creating lateral heterojunctions in two-dimensional materials. These heterojunctions have rectifying properties and are formed by immersing a coordination nanosheet made from zinc ions and benzenehexathiol into iron and copper salt solutions. This research has implications for utilizing the attractive properties of two-dimensional materials more effectively. The authors of the article include Choon Meng Tan, Naoya Fukui, Kenji Takada, Hiroaki Maeda, Ekaterina Selezneva, Cédric Bourgès, Hiroyasu Masunaga, Sono Sasaki, Kazuhito Tsukagoshi, Takao Mori, Henning Sirringhaus, and Hiroshi Nishihara. [Extracted from the article]

In an article published in Angewandte Chemie, Hiroshi Nishihara et al. present a new method for creating lateral heterojunctions in two-dimensional materials. These heterojunctions have rectifying properties and can be fabricated by immersing a coordination nanosheet made from zinc ions and benzenehexathiol into iron and copper salt solutions. This research has implications for utilizing the attractive properties of two-dimensional materials more effectively. The authors of the article include Choon Meng Tan, Naoya Fukui, Kenji Takada, Hiroaki Maeda, Ekaterina Selezneva, Cédric Bourgès, Hiroyasu Masunaga, Sono Sasaki, Kazuhito Tsukagoshi, Takao Mori, Henning Sirringhaus, and Hiroshi Nishihara. [Extracted from the article]

Amaranthus tricolor L., a vegetable Amaranthus species, is an economically important crop containing large amounts of betalains. Betalains are natural antioxidants and can be classified into betacyanins and betaxanthins, with red and yellow colors, respectively. A. tricolor cultivars with varying betalain contents, leading to striking red to green coloration, have been commercially produced. However, the molecular differences underlying betalain biosynthesis in various cultivars of A. tricolor remain largely unknown. In this study, A. tricolor cultivars with different colors were chosen for comparative transcriptome analysis. The elevated expression of AmCYP76AD1 in a red-leaf cultivar of A. tricolor was proposed to play a key role in producing red betalain pigments. The functions of AmCYP76AD1, AmDODAα1, AmDODAα2, and AmcDOPA5GT were also characterized through the heterologous engineering of betalain pigments in Nicotiana benthamiana. Moreover, high and low L-DOPA 4,5-dioxygenase activities of AmDODAα1 and AmDODAα2, respectively, were confirmed through in vitro enzymatic assays. Thus, comparative transcriptome analysis combined with functional and enzymatic studies allowed the construction of a core betalain biosynthesis pathway of A. tricolor. These results not only provide novel insights into betalain biosynthesis and evolution in A. tricolor but also provide a basal framework for examining genes related to betalain biosynthesis among different species of Amaranthaceae. [ABSTRACT FROM AUTHOR]

XopDXcc 8004, a type III effector of Xanthomonas campestris pv. campestris (Xcc) 8004, is considered a shorter version of the XopD, which lacks the N-terminal domain. To understand the functions of XopDXcc 8004, in planta, a transgenic approach combined with inducible promoter to analyze the effects of XopDXcc 8004 in Arabidopsis was done. Here, the expression of XopDXcc 8004, in Arabidopsis elicited the accumulation of host defense-response genes. These molecular changes were dependent on salicylic acid and correlated with lesion-mimic phenotypes observed in XVE::XopDXcc8004 transgenic plants. Moreover, XopDXcc 8004 was able to desumoylate HFR1, a basic helix-loop-helix transcription factor involved in photomorphogenesis, through SUMO protease activity. Interestingly, the hfr1-201 mutant increased the expression of host defense-response genes and displayed a resistance phenotype to Xcc8004. These data suggest that HFR1 is involved in plant innate immunity and is potentially regulated by XopDXcc 8004. [ABSTRACT FROM AUTHOR]

XopDXcc 8004, a type III effector of Xanthomonas campestris pv. campestris (Xcc) 8004, is considered a shorter version of the XopD, which lacks the N-terminal domain. To understand the functions of XopDXcc 8004, in planta, a transgenic approach combined with inducible promoter to analyze the effects of XopDXcc 8004 in Arabidopsis was done. Here, the expression of XopDXcc 8004, in Arabidopsis elicited the accumulation of host defense-response genes. These molecular changes were dependent on salicylic acid and correlated with lesion-mimic phenotypes observed in XVE::XopDXcc8004 transgenic plants. Moreover, XopDXcc 8004 was able to desumoylate HFR1, a basic helix-loop-helix transcription factor involved in photomorphogenesis, through SUMO protease activity. Interestingly, the hfr1-201 mutant increased the expression of host defense-response genes and displayed a resistance phenotype to Xcc8004. These data suggest that HFR1 is involved in plant innate immunity and is potentially regulated by XopDXcc 8004. [ABSTRACT FROM AUTHOR]

Digera muricata (L.) Mart. is a pantropical annual herb belonging to the Amaranthaceae family. In August 2021, D. muricata with indicative phytoplasma symptoms of phyllody, witches'-broom, and virescence was discovered adjacent to a peanut field in Mailiao, Yunlin, Taiwan. The causal agent of the observed symptoms was detected and identified by a series of molecular characterizations. Sieve elements of the phloem tissue were perused under the transmission electron microscope and revealed the presence of pleomorphic phytoplasma-like organisms. Nested PCR using phytoplasma universal primer pairs P1/P7 and R16F2n/R16R2 was able to amplify a 1.2-kb DNA fragment for the 16S rRNA gene only from the symptomatic D. muricata . The 16S rRNA -based phylogenetic analysis and the i PhyClassifier-based virtual RFLP further affirmed that the phytoplasma associated with the diseased D. muricata can be classified into the 16SrII-V subgroup. Moreover, displayed evident symptoms were explained by the concomitant detection of PHYL1 and SAP11 , the virulence genes responsible for the development of leaf-like flowers and shoot proliferation, respectively. Although phytoplasma infection on the noncrop species does not have a direct economic impact, its role in disease spread and perpetuation is indubitable.

Eclipta prostrata (L.), commonly known as false daisy of the family Asteraceae, is an erect or prostrate annual herb that grows 5 to 45 cm tall. It is widespread mainly in tropical and subtropical regions like India, China, Taiwan, Thailand, and Brazil (Chung et al., 2017). E. prostrata has very wide medicinal properties accounted by several phytochemicals like thiophene derivatives, steroids, flavonoids, and polypeptides (Feng et. al., 2019). It is also used as a traditional herbal medicine for the treatment of bleeding, hemoptysis and itching, hepatitis diarrhea, and even hair loss (Timalsina et al., 2021). In September 2021, E. prostrata displaying branch proliferation and phyllody symptoms with about 30% (6 were symptomatic and 14 were healthy) incidence rate was observed in Mailiao, Yunlin, Taiwan where phytoplasma disease is permeating and has affected many crops and non-crop species including peanut, mungbean, curl-leaved tobacco, false amaranth, etc. Compared to healthy E. prostrata bearing white ray florets and cream or dull white disk florets, symptomatic ones developed phyllody which is more pronounced on the severely infected ones. Further examination by transmission electron microscope revealed a pleomorphic (circular, elliptical, and bell-shaped) phytoplasma-like organisms accumulated in the sieve elements of the symptomatic leaves. Phytoplasma infection was further confirmed by nested polymerase chain reaction using universal primers P1/P7 (carried out for 12 cycles), followed by R16F2n/R16R2 (carried out for 35 cycles) on the genomic DNA extracted by Plant Genomic DNA Purification Kit (DP022-150, GeneMark) (Lee et al. 1993). Results revealed that the conserved 16S rRNA gene with a 1.2 kb fragment size was amplified only by the symptomatic samples. Furthermore, western blotting was done using the polyclonal antibody raised against the immunodominant membrane protein (Imp) of peanut witches'-broom (PnWB) phytoplasma, a ' Candidatus Phytoplasma aurantifolia' in Taiwan that belongs group to 16SrII (Chen et al. 2021). Consistent with the nested PCR, only the symptomatic samples revealed a specific Imp signal with a size of 19 kDa. To classify the phytoplasma associated with the symptomatic E. prostrata , the DNA sequence (No. OM397418) of the P1/P7 primer pair-amplified DNA fragment was obtained using P1 and a nested primer (5'-GGGTCTTTACTGACGCTGAGG-3'), which shares 100% identity with that of GenBank accession NZ_AMWZ01000008 (complement [31109 to 32640]) of PnWB phytoplasma. Further analysis of the virtual RFLP pattern of OM397418 by i PhyClassifier confirmed that the phytoplasma identified in the symptomatic E. prostrata belongs 16SrII-V subgroup. To the best of our knowledge, this is the first report of phytoplasma disease in E. prostrata associated with the ' Ca . P. aurantifolia' in Taiwan.

Nicotiana plumbaginifolia Viviani, commonly known as curl-leaved tobacco, is an annual herbaceous plant belonging to Solanaceae family. This plant is native to Mexico, South America, and parts of the Caribbean and has been reported to be present in Taiwan since 2006. In March 2021, N. plumbaginifolia Viviani, found in Yunlin County, Taiwan, was observed to have phyllody, virescence, and witches'-broom, which is consistent with the disease symptoms caused by phytoplasma infection. Samples of the healthy and symptomatic plants were collected for analysis of the causal agent associated with the diseased N. plumbaginifolia Viviani. Under transmission electron microscopy, the phytoplasma-like pleomorphic bodies were found in the sieve tubes of the diseased plants. The 16S ribosomal RNA (rRNA)-based phylogenetic analysis and the i PhyClassifier-based virtual restriction fragment length polymorphism study demonstrated that the phytoplasma identified in this study can be classified into the 16SrII-V subgroup, which is similar to the peanut witches'-broom phytoplasma, a ' Candidatus phytoplasma aurantifolia'-related strain. Further identification of SAP54/PHYL1 and SAP11 homologs in the phytoplasma explain the disease symptoms of phyllody, virescence, and witches'-broom observed in diseased N. plumbaginifolia Viviani. The discovery of new phytoplasma plant hosts has gained scientific importance in light of the attempt to unravel an efficient strategy to fight the rapid spread of this disease, which poses a threat to the agricultural sector and food security in Taiwan.

Mungbean ( Vigna radiata (L.) R. Wilczek), an important legume crop in Asia, is primarily cultivated in the central-southern region of western Taiwan. In 2020, mungbean exhibiting typical phytoplasma-induced disease symptoms such as witches' broom, phyllody, virescence, and proliferation was observed in Yunlin County, Taiwan. Moreover, the seed harvested from diseased plants displayed premature germination. Transmission electron microscopy examination of leaf veins prepared from symptomatic mungbean demonstrated that the occlusion of sieve tubes resulted from the accumulation of phytoplasma-like bodies in sieve elements along with filament-like structures in sieve pores. The association of phytoplasma in symptomatic mungbean was confirmed by PCR analyses of the 16S ribosomal RNA (rRNA) and immunodominant membrane protein genes. Further analyses of the 16S rRNA-based phylogenetic tree and the i PhyClassifier-based virtual restriction fragment length polymorphism study demonstrated that the phytoplasma-associated mungbean phyllody disease identified in this study belongs to the 16SrII-V subgroup. BLAST analysis and the phylogenetic analysis indicated that the SAP11-like protein identified in mungbean phyllody disease is identical to peanut witches' broom phytoplasma SAP11, which explains the witches' broom phenotype observed in symptomatic mungbean. The results described in this report confirm that the 16SrII-V phytoplasma, a widely distributed phytoplasma associated with peanut witches' broom disease in Taiwan, has also infected mungbean. This is not only the first instance of mungbean phyllody disease found in Taiwan but also the first instance of mungbean phyllody disease caused by 16SrII-V subgroup phytoplasma.

Three-flower Tick-clover ( Desmodium triflorum ) is a perennial herbaceous plant that belongs to the family of Leguminosae. Threeflower tickclover widely grows at mid-low altitude regions in Taiwan and is commonly used as a traditional herbal medicine for the treatment of dysmenorrheal, muscle spasm, cough, pain and poisoning. In March 2020, disease symptoms such as little leaf, phyllody, virescence, and witches' broom were observed on threeflower tickclover at the sansheng community park in Mailiao, Yunlin County, Taiwan. Similar disease symptoms were observed on peanut infected with peanut witches' broom (PnWB) phytoplasma grown in the same area (Liu et al. 2015). Leaf samples collected from the healthy and symptomatic threeflower tickclover were used to extract total DNA and protein for PCR and western blotting assays, respectively. Nested PCR was performed with the phytoplasma universal primer pairs P1/P7 followed by R16F2n/R16R2 for the amplification of 16S ribosomal RNA (rRNA) gene (Lee et al. 1993). A specific DNA fragment of expected size (1.2 kb) for 16S rRNA was only amplified from leaf samples of symptomatic threeflower tickclover. The nucleotide sequence of the amplified DNA fragment using primer pairs P1/P7 was deposited into the GenBank (accession no. MT452308). Blast analysis revealed that MT452308 shares 100% identity with that of GenBank accession NZ_AMWZ01000008 (complement [31109 to 32640]) of phytoplasma associated with PnWB disease (Chung et al. 2013). Based on the virtual RFLP pattern of MT452308 generated by i PhyClassifier, the phytoplasma detected in symptomatic threeflower tickclover could be classified into the 16SrII-V subgroup. For western blotting, the polyclonal antibody raised against Imp protein of purple coneflower witches' broom phytoplasma (Chien et al. 2020), which is identical with that (accession no. ADD59806) of PnWB phytoplasma, was used. An expected signal of 19 kDa specific for Imp was only detected in threeflower tickclover exhibiting disease symptoms. Subsequent assays including PCR, DNA sequencing and western blotting further confirmed that the gene encoding a SAP11-like protein (accession no. EMR14684) identified in PnWB phytoplasma was also found in samples of symptomatic threeflower tickclover, and shares 100% identity with each other. Our results indicate that threeflower tickclover, a common weed in Taiwan, may act as an alternative natural host for PnWB phytoplasma, and contributes to the spreading of phytoplasma disease.

Ixeris chinensis (Thunb. ex Thunb.) Nakai, a perennial herbaceous plant that belongs to the family of Asteraceae, is widely distributed at mid-low altitude regions in Taiwan. I. chinensis is commonly used as traditional herbal medicine for the treatment of inflammation, bronchitis, pneumonia, and diarrhea. In March 2020, disease symptoms such as shoot proliferation, phyllody, virescence, purple top, and witches' broom were observed on I. chinensis at the sansheng community park in Mailiao, Yunlin County, Taiwan. Totally, eight I. chinensis plants were checked and half of them were symptomatic. These disease symptoms are similar to those associated with peanut witches' broom (PnWB) disease identified in the same area (Liu et al. 2015). Three samples mixed with leaf, stem, and flower were tested including one healthy and two symptomatic I. chinensis . The total DNA of each sample was extracted and examined by nested PCR for the amplification of 16S rDNA with the phytoplasma universal primer pairs P1/P7 followed by R16F2n/R16R2 (Lee et al. 1993). A specific signal of expected size (1.2 kb) for 16S rDNA was only detected in the symptomatic I. chinensis , but not in healthy I. chinensis . The nucleotide sequence (accession no. MT416114) of the amplified DNA fragment using primer pairs P1/P7 from symptomatic I. chinensis is identical to that of GenBank accession NZ_AMWZ01000008 (complement [31109 to 32640]) of phytoplasma associated with PnWB disease (Chung et al. 2013). Analysis of the virtual RFLP pattern of MT416114 generated by iPhyClassifier revealed that the phytoplasma detected in symptomatic I. chinensis belongs to a 16SrII-V subgroup. The total protein of each sample was also extracted and examined by western blotting using the polyclonal antibody raised against Imp protein of purple coneflower witches' broom phytoplasma (Chien et al. 2020), which is identical with that (accession no. ADD59806) of PnWB phytoplasma. An expected signal of 19 kDa specific for Imp was detected in symptomatic I. chinensis , but not in healthy I. chinensis . Subsequent PCR, DNA sequencing and western blotting assays further confirmed that the gene encoding a SAP11-like protein was only detected in symptomatic I. chinensis , and shares 100% identity with that (accession no. EMR14684) of PnWB phytoplasma. Our results indicate that PnWB phytoplasma causes disease in I. chinensis , a common weed, which may act as an alternative natural host and facilitate the spreading of phytoplasma disease in Taiwan.

Lilac tasselflower ( Emilia sonchifolia ) is an annual herbaceous plant that belongs to the family of Asteraceae. Lilac tasselflower is widely distributed at mid-low altitude regions in Taiwan, and is commonly used as traditional herbal medicine for the treatment of inflammation, rheumatism, dysentery, and analgesic. In March 2020, disease symptoms such as shoot proliferation, phyllody, and witches' broom were observed on lilac tasselflower at the sansheng community park in Mailiao, Yunlin County, Taiwan. Totally, four lilac tasselflower plants were checked and half of them were symptomatic. At the same area, similar symptoms associated with peanut witches' broom (PnWB) disease were observed (Liu et al. 2015). Samples including one healthy and two symptomatic lilac tasselflower were collected for total DNA and protein extraction used for PCR and western blotting assays, respectively. First, two sets of phytoplasma universal primer pairs P1/P7 and R16F2n/R16R2 were used to perform nested PCR for detection of 16S ribosomal RNA (rRNA) gene (Lee et al. 1993). A specific signal of expected size (1.2 kb) for 16S rRNA was only detected in samples of lilac tasselflower exhibiting disease symptoms. The amplified DNA fragment using primer pairs P1/P7 was partially sequenced (accession no. MT420682) with P1 and a nested primer (5'-GGGTCTTTACTGACGCTGAGG-3'). The 1.4 kb nucleotide sequence shares 100% identity with that of GenBank accession NZ_AMWZ01000008 (complement [31109 to 32640]) of phytoplasma associated with PnWB disease (Chung et al. 2013). Further analysis by i PhyClassifier, the virtual RFLP pattern of MT420682 confirmed that the phytoplasma detected in symptomatic lilac tasselflower could be classified into the 16SrII-V subgroup. For western blotting, total protein of each sample was examined using the polyclonal antibody raised against Imp protein of purple coneflower witches' broom phytoplasma (Chien et al. 2020), which shares 100% identity with that (accession no. ADD59806) of PnWB phytoplasma. A specific signal of expected size (19 kDa) for Imp was detected in symptomatic lilac tasselflower, but not in healthy lilac tasselflower. Subsequent PCR, DNA sequencing and western blotting assays further confirmed that the gene encoding a SAP11-like protein detected in samples of lilac tasselflower exhibiting disease symptoms is identical to that (accession no. EMR14684) of PnWB phytoplasma. Our results indicated that lilac tasselflower, which is recognized as a common weed in Taiwan, may facilitate the spreading of phytoplasma disease by acting as an alternative natural host for PnWB phytoplasma.

XopDXcc8004, a type III effector of Xanthomonas campestris pv. campestris (Xcc) 8004, is considered a shorter version of the XopD, which lacks the N-terminal domain. To understand the functions of XopDXcc8004, in planta, a transgenic approach combined with inducible promoter to analyze the effects of XopDXcc8004 in Arabidopsis was done. Here, the expression of XopDXcc8004, in Arabidopsis elicited the accumulation of host defense-response genes. These molecular changes were dependent on salicylic acid and correlated with lesion-mimic phenotypes observed in XVE::XopDXcc8004 transgenic plants. Moreover, XopDXcc8004 was able to desumoylate HFR1, a basic helix-loop-helix transcription factor involved in photomorphogenesis, through SUMO protease activity. Interestingly, the hfr1-201 mutant increased the expression of host defense-response genes and displayed a resistance phenotype to Xcc8004. These data suggest that HFR1 is involved in plant innate immunity and is potentially regulated by XopDXcc8004.

Plant disease induced by Xanthomonas campestris pv. campestris depends on type III effectors but the molecular basis is poorly understood. Here, AvrXccC8004 was characterized, and it was found that the AvrB_AvrC domain was essential and sufficient to elicit defense responses in an Arabidopsis-resistant ecotype (Col-0). An upregulation of genes in responding to the AvrB_AvrC domain of AvrXccC8004 was shown in a profile of host gene expression. The molecular changes were correlated with morphological changes observed in phenotypic and ultrastructural characterizations. Interestingly, the abscisic acid (ABA)-signaling pathway was also a prominent target for the AvrB_AvrC domain of AvrXccC8004. The highly elicited NCED5, encoding a key enzyme of ABA biosynthesis, was increased in parallel with ABA levels in AvrXccC8004 transgenic plants. Consistently, the X. campestris pv. campestris 8004 ΔavrXccC mutant was severely impaired in the ability to manipulate the accumulation of ABA and induction of ABA-related genes in challenged leaves. Moreover, exogenous application of ABA also enhanced the susceptibility of Arabidopsis to the X. campestris pv. campestris strains. These results indicate that the AvrB_AvrC domain of AvrXccC8004 alone has the activity to manipulate ABA homeostasis, which plays an important role in regulating the interactions of X. campestris pv. campestris and Arabidopsis.