Molecular plant pathology最新文献

Microbial pathogens and other parasites can modify the development of their hosts, either as a target or a side effect of their virulence activities. The plant-pathogenic bacterium Ralstonia solanacearum, causal agent of the devastating bacterial wilt disease, is a soilborne microbe that invades host plants through their roots and later proliferates in xylem vessels. In this work, we studied the early stages of R. solanacearum infection in the model plant Arabidopsis thaliana, using an in vitro infection system. In addition to the previously reported inhibition of primary root length and increase in root hair formation at the root tip, we observed an earlier xylem differentiation during R. solanacearum infection that occurs in a HrpG-dependent manner, suggesting that the pathogen actively promotes the development of the vascular system upon invasion of the root. Moreover, we found that the phytohormone auxin, of which the accumulation is promoted by the bacterial infection, is required for the R. solanacearum-triggered induction of root hair formation but not earlier xylem differentiation. Altogether, our results shed light on the capacity of R. solanacearum to induce alterations of root developmental pathways and on the role of auxin in this process.

Zhu, L.-J., Zhu, Y., Zou, C., Su, L.-Y., Zhang, C.-T., Wang, C. et al. (2024) New persistent plant RNA virus carries mutations to weaken viral suppression of antiviral RNA interference. Molecular Plant Pathology, 25, e70020. Available from: https://doi.org/10.1111/mpp.70020 The following errors have been identified in the above published article: The co-first authors and co-corresponding authors are not indicated. The order of the funds appearing in the Funding information of the article are not consistent with the order in the Acknowledgements. The authors would like to correct these errors as follows: Li-Juan Zhu and Yu Zhu contributed equally to this work. Jian-Guo Wu and Yan-Hong Han are co-corresponding authors. Jiang-Guo Wu: wujianguo81@126.com; Yan-Hong Han: yan-hong@fafu.edu The correct order of funds is: National Natural Science Foundation of China, Grant/Award Number 32025031 and 31,900,153, National Key Research and Development Program of China, Grant/Award Number 2023YFF1000500 and Special Fund Project for Science and Technology Innovation of FAFU, Grant/Award Number KFB23013. We apologise for these errors.

The organs of a plant species vary in cell structure, metabolism and defence responses. However, the mechanisms that enable a single pathogen to colonise different plant organs remain unclear. Here we compared the transcriptome of the oomycete pathogen Phytophthora sojae during infection of roots versus leaves of soybeans. We found differences in the transcript levels of hundreds of pathogenicity-related genes, particularly genes encoding carbohydrate-active enzymes, secreted (effector) proteins, oxidoreductase-related proteins and transporters. To identify the key regulator for root-specific infection, we knocked out root-specific transcription factors (TFs) and found the mutants of PsBZPc29, which encodes a member of an oomycete-specific class of basic leucine zipper (bZIP) TFs, displayed reduced virulence on soybean roots but not on leaves. More than 60% of the root-specific genes showed reduced expression in the mutants during root infection. The results suggest that transcriptional regulation underlies the organ-specific infection by P. sojae, and that a bZIP TF plays a key role in root-specific transcriptional regulation.

Viroids are single-stranded circular noncoding RNAs that mainly infect crops. Upon infection, nuclear-replicating viroids engage host DNA-dependent RNA polymerase II for RNA-templated transcription, which is facilitated by a host protein TFIIIA-7ZF. The sense-strand and minus-strand RNA intermediates are differentially localised to the nucleolus and nucleoplasm regions, respectively. The factors and function underlying the differential localisation of viroid RNAs have not been fully elucidated. The sense-strand RNA intermediates are cleaved into linear monomers by a yet-to-be-identified RNase III-type enzyme and ligated to form circular RNA progeny by DNA ligase I (LIG1). The subcellular compartment for the ligation reaction has not been characterised. Here, we show that LIG1 and potato spindle tuber viroid (PSTVd) colocalise near the nucleolar region in Nicotiana benthamiana protoplasts. The colocalised region is also the highly condensed region of sense-strand PSTVd RNA, indicating that PSTVd RNA and LIG1 form a biomolecular condensate for RNA processing. This finding expands the function of biomolecular condensates to the infection of subviral pathogens. In addition, this knowledge of viroid biogenesis will contribute to exploring thousands of viroid-like RNAs that have been recently identified.

Streptomyces scabies is a well-researched plant pathogen belonging to the genus Streptomyces. Its virulence is linked to the production of the secondary metabolite thaxtomin A, which is tightly regulated at the transcriptional level. The leucine-responsive regulatory protein (Lrp) family is conserved in prokaryotes and is involved in various crucial biological processes. However, the regulatory interaction between Lrp protein and pathogenic Streptomyces species remains poorly understood. This study aims to explore the role of SCAB_Lrp2 in regulating thaxtomin biosynthesis and pathogenicity, and to analyse the shared and unique features of Lrp homologues in S. scabies. We observed that SCAB_Lrp2 (SCAB_75421) showed significant homology with SCAB_Lrp, a recognised activator of thaxtomin A production in S. scabies. Our results revealed a regulatory interaction between SCAB_Lrp2 and SCAB_Lrp in terms of their targets, although SCAB_Lrp2 does not respond to the amino acid-effectors of SCAB_Lrp. In contrast to SCAB_Lrp, deletion of SCAB_Lrp2 resulted in a notable increase in thaxtomin A production with the emergence of a hypervirulent phenotype in S. scabies. Further analysis revealed that SCAB_Lrp2 represses the transcription of the thaxtomin biosynthetic gene cluster by directly regulating the cluster-situated regulator (CSR) gene txtR. Moreover, the precursor of thaxtomin, tryptophan, acts as an effector of SCAB_Lrp2, strengthening the repressive effect on thaxtomin biosynthesis through txtR. These findings provide new insights into the functional conservation and diversity of Lrp homologues involved in the biosynthesis of thaxtomin phytotoxins in pathogenic Streptomyces species.

Wei, Y.X., Liu, G.Y., Chang, Y.L., He, C.Z., Shi, H.T. Heat Shock Transcription Factor 3 Regulates Plant Immune Response Through Modulation of Salicylic Acid Accumulation and Signalling in Cassava. Molecular Plant Pathology, 2018; 19: 2209-2220. In the above article, there were unintentional errors in Figure 3 and Figure 6, specifically in the images of 0 dpi at Figure 3B and 6 dpi (pTRV-MeEDS1, pTRV-MePR4) at Figure 6C. These errors have been corrected in the below images: Corrected Figure 3 Corrected Figure 6 We apologise for these errors.

The compound appressoria of Sclerotinia sclerotiorum can produce cell wall-degrading enzymes, effectors and toxins, which promote penetration and the death of host cells. Subsequently, invasive hyphae (IH) branch rapidly as necrotrophic growth and disease symptoms are observed. S. sclerotiorum can respond to complex stresses and regulate its metabolism to adapt to the external environment. Here we demonstrated that type 2C Ser/Thr phosphatase (PP2C) SsPtc3 responds to nutritional, osmotic, cell wall and oxidative stresses. Loss of function ΔSsptc3 mutants displayed defects in mycelial growth, sclerotia formation and reduced virulence. Phosphoproteomic analyses revealed that SsPtc3 is involved in autophagy and MAPK signalling pathways. We obtained evidence that SsPtc3 negatively modulates the phosphorylation of SsSmk1. SsSmk1 is essential for mycelial growth, compound appressorium formation and pathogenicity, SsPtc3 modulated phosphorylation homeostasis of SsSmk1 to maintain hyphal growth. SsPtc3 interacted with SsAtg1 to influence autophagic flux under starvation. Taken together, these results reveal that SsPtc3 responds to various stresses that modulate autophagy and phosphorylation of SsSmk1-MAPK, which facilitates the growth and virulence of S. sclerotiorum.

In Arabidopsis thaliana, the transcription factors WRKY7, WRKY11 and WRKY17 act as negative defence regulators against Pseudomonas syringae pv. tomato (Pst) DC3000. However, their coordinated regulation of gene expression has yet to be fully explored. In this study, we conducted a transcriptomic analysis on the triple mutant wrky7/11/17 in response to Pst DC3000 at 0, 3 and 24 h post-inoculation (hpi). Our results suggest that at early infection stages (0 and 3 hpi), WRKY7, WRKY11 and WRKY17 significantly repress a group of genes involved in signal perception and transduction, including receptor-like kinases. Furthermore, at later stages of interaction (24 hpi), these transcription factors induce genes related to the biosynthesis and signalling of the jasmonic acid (JA) pathway. Further infection experiments with Pst DC3000 in plants treated with methyl jasmonate (a JA analogue) and infections with Botrytis cinerea, a pathogen against which JA-mediated responses are crucial for effective defence, support this proposal. Moreover, we analysed the role of WRKY7, WRKY11 and WRKY17 in alternative splicing regulation. A comparison between differentially expressed (DEG) and spliced (DAS) genes revealed that over 80% of DAS events do not occur in conjunction with overall changes in gene expression. Alternative splicing events were found in genes with functions in splicing and the JA pathway, such as ALY4, PRP40A, JAZ3 and JAZ10. These results suggest that WRKY7, WRKY11 and WRKY17 can also participate in this layer of gene expression regulation to modulate immunity negatively.

Cytokinin signalling plays both positive and negative roles in plant resistance to pathogens. It is not clear whether the role of cytokinin changes at the different stages of pathogen infection. Arabidopsis thaliana sequentially exhibits distinct root morphological symptoms during Ralstonia solanacearum infection, which offers a good system to investigate function of cytokinin in the whole pathogen infection process. Using this system, we found increase of cytokinin signalling by Lonely Guy 2 (LOG2) overexpression or depletion of type-A Arabidopsis Response Regulators (ARRs), negative regulators of cytokinin signalling pathway, promoted cell death, wilting symptom and bacterial growth, but attenuated primary root growth inhibition and lateral root formation. The decrease of cytokinin signalling by mutation on Isopentenyl Transferases (IPTs) inhibited root hair formation, cell death, wilting symptom and bacterial colonisation. Application of different concentration of exogenesis 6-benzylaminopurine (6-BA) showed first promoted, then decreased root hair formation. Moreover, application of 6-BA accelerated cell death but suppressed lateral root formation and primary root growth inhibition. The diverse roles of cytokinin in these different root disease phenotypes suggested function of cytokinin during plant responses to R. solanacearum is cell type-specific, which provides new insights on roles of cytokinin signalling in regulation on plant-pathogen interactions.

Bacteria employ two-component systems (TCSs) to rapidly sense and respond to their surroundings often and during plant infection. Poplar canker caused by Lonsdalea populi is an emerging woody bacterial disease that leads to high mortality and poplar plantation losses in China. Nonetheless, the information about the underlying mechanism of pathogenesis remains scarce. Therefore, in this study, we reported the role of a TCS pair CpxA/CpxR in regulating virulence and stress responses in L. populi. The CpxA/R system is essential during infection, flagellum formation, and oxidative stress response. Specifically, the Cpx system affected flagellum formation by controlling the expression of flagellum-related genes. CpxR, which was activated by phosphorylation in the presence of CpxA, participated in the transcriptional regulation of a chaperone sctU and the type III secretion system (T3SS)-related genes, thereby influencing T3SS functions during L. populi infection. Phosphorylated CpxR directly manipulated the transcription of a membrane protein-coding gene yccA and the deletion of yccA resulted in reduced virulence and increased sensitivity to H₂O₂. Furthermore, we mutated the conserved phosphorylation site of CpxR and found that CpxR^D51A could no longer bind to the yccA promoter but could still bind to the sctU promoter. Together, our findings elucidate the roles of the Cpx system in regulating virulence and reactive oxygen species resistance and provide further evidence that the TCS is crucial during infection and stress response.