Marta Michniewicz, Cheng-Hsun Ho, Tara A. Enders, Eric Floro, Suresh Damodaran, Lauren K. Gunther, Samantha K. Powers, Elizabeth M. Frick, Christopher N. Topp, Wolf B. Frommer, and Lucia C. Strader (2019). TRANSPORTER OF IBA1 Links Auxin and Cytokininto Influence Root Architecture. Developmental Cell 2019. In press. (https://www.sciencedirect.com/science/article/pii/S1534580719305283)
Developmental processes that control root system architecture are critical for soil exploration by plants, allowing for uptake of water and nutrients. Conversion of the auxin precursor indole-3-butyric acid (IBA) to active auxin (indole-3-acetic acid; IAA) modulates lateral root formation. However, mechanisms governing IBA-to-IAA conversion have yet to be elucidated. We identified TRANSPORTER OF IBA1 (TOB1) as a vacuolar IBA transporter that limits lateral root formation. Moreover, TOB1, which is transcriptionally regulated by the phytohormone cytokinin, is necessary for the ability of cytokinin to exert inhibitory effects on lateral root production. The increased production of lateral roots in tob1 mutants, TOB1 transport of IBA into the vacuole, and cytokinin-regulated TOB1 expression provide a mechanism linking cytokinin signaling and IBA contribution to the auxin pool to tune root system architecture.
Yi-Shu Chiu, Pi-Yu Chen, Tung Kuan, Po-Chuan Wang, Ying-Ju Chen, Yu-Liang Yang* and Hsin-Hung Yeh* (2018) A Polysaccharide derived from a Trichosporon sp. culture strongly primes plant resistance to viruses. MPMI. https://doi.org/10.1094/MPMI-01-18-0012-R
Plant viruses cause devastating diseases in plants, yet no effective viricide is available for agricultural application. We screened cultured filtrates derived from various soil microorganisms cultured in vegetable broth that enhanced plant viral resistance. A cultured filtrate, designated F8 culture filtrate, derived from a fungus belonging to the genus Trichosporon, induced strong resistance to various viruses on different plants. Our inoculation assay found the infection rate of Tobacco mosaic virus (TMV)-inoculated Nicotiana benthamiana with F8 culture filtrate pretreatment may decrease to 0%, whereas salicylic acid (SA)-pretreated N. benthamiana attenuated TMV-caused symptoms but remained 100% infected. Tracking Tobacco mosaic virus tagged with green fluorescence protein in plants revealed pretreatment with F8 culture filtrate affected the initial establishment of the virus infection. From F8 culture filtrate, we identified a previously unknown polysaccharide composed of D-mannose, D-galactose, and D-glucose in the ratio 1.0:1.2:10.0 with a α-D-1,4-glucan linkage to be responsible for the induction of plant resistance against viruses through priming of SA-governed immune-responsive genes. Notably, F8 culture filtrate only triggered local defense but was much more effective than conventional SA-mediated systematic acquired resistance. Our finding revealed that microbial cultured metabolites provided a rich source for identification of potent elicitors in plant defense.
Li Chang, Ho-Hsiung Chang, Jui-Che Chang, Hsiang-Chia Lu, Tan-Tung Wang, Duen-Wei Hsu, Yuh Tzean, An-Po Cheng, Yi-Shu Chiu and Hsin-Hung Yeh* (2018) Plant A20/AN1 protein serves as the important hub to mediate antiviral immunity. PLoS Pathog. https://doi.org/10.1371/journal.ppat.1007288
Salicylic acid (SA) is a key phytohormone that mediates a broad spectrum of resistance against a diverse range of viruses; however, the downstream pathway of SA governed antiviral immune response remains largely to be explored. Here, we identified an orchid protein containing A20 and AN1 zinc finger domains, designated Pha13. Pha13 is up-regulated upon virus infection, and the transgenic monocot orchid and dicot Arabidopsis overexpressing orchid Pha13 conferred greater resistance to different viruses. In addition, our data showed that Arabidopsis homolog of Pha13, AtSAP5, is also involved in virus resistance. Pha13 and AtSAP5 are early induced by exogenous SA treatment, and participate in the expression of SA-mediated immune responsive genes, including the master regulator gene of plant immunity, NPR1, as well as NPR1-independent virus defense genes. SA also induced the proteasome degradation of Pha13. Functional domain analysis revealed that AN1 domain of Pha13 is involved in expression of orchid NPR1, whereas dual A20/AN1 domains orchestrated the overall virus resistance. Subcellular localization analysis suggested that Pha13 can be found localized in the nucleus. Self-ubiquitination assay revealed that Pha13 confer E3 ligase activity, and the main E3 ligase activity was mapped to the A20 domain. Identification of Pha13 interacting proteins and substrate by yeast two-hybrid screening revealed mainly ubiquitin proteins. Further detailed biochemical analysis revealed that A20 domain of Pha13 binds to various polyubiquitin chains, suggesting that Pha13 may interact with multiple ubiquitinated proteins. Our findings revealed that Pha13 serves as an important regulatory hub in plant antiviral immunity, and uncover a delicate mode of immune regulation through the coordination of A20 and/or AN1 domains, as well as through the modulation of E3 ligase and ubiquitin chain binding activity of Pha13.
Chih-Cheng Lin, Ya-Ting Chao, Wan-Chieh Chen, Hsiu-Yin Ho, Mei-Yi Chou, Ya-Ru Li, Yu-Lin Wu, Hung-An Yang, Hsiang Hsieh, Choun-Sea Lin, Fu-Hui Wu, Shu-Jen Chou, Hao-Chung Jen, Yung-Hsiang Huang, Deli Irene, Wen-Jin Wu, Jian-Li Wu, Daniel J. Gibbs, Meng-Chiao Ho*, and Ming-Che Shih* (2019) Regulatory cascade involving transcriptional and N-end rule pathways in rice under submergence. Proc. Natl. Acad. Sci., published ahead of print February 5, 2019. https://doi.org/10.1073/pnas.1818507116
The rice SUB1A-1 gene, which encodes a group VII ethylene response factor (ERFVII) plays a pivotal role in rice survival under flooding stress, as well as other abiotic stresses. In Arabidopsis, five ERFVII factors play roles in regulating hypoxic responses. A characteristic feature of Arabidopsis ERFVIIs is a destabilizing N-terminus, which functions as an N-degron that targets them for degradation via the oxygen-dependent N-end rule pathway of proteolysis, but permits their stabilization during hypoxia for hypoxia-responsive signaling. Despite having the canonical N-degron sequence, SUB1A-1 is not under N-end rule regulation, suggesting a distinct hypoxia signaling pathway in rice during submergence. Herein we show that two other rice ERFVIIs, ERF66 and ERF67, are directly transcriptionally up-regulated by SUB1A-1 under submergence. In contrast to SUB1A-1, ERF66 and ERF67 are substrates of the N-end rule pathway, which are stabilized under hypoxia and may be responsible for triggering a stronger transcriptional response to promote submergence survival. In support of this, overexpression ERF66 or ERF67 leads to activation of anaerobic survival genes and enhanced submergence tolerance. Furthermore, using structural and protein-interaction analyses, we show that the C-terminus of SUB1A-1 prevents its degradation via the N-end rule and directly interacts with the SUB1A-1 N-terminus, which may explain enhanced stability of SUB1A-1 despite bearing an N-degron sequence. In summary, our results suggest that SUB1A-1, ERF66, and ERF67 form a regulatory cascade involving transcriptional and N-end rule control, which allows rice to distinguish flooding from other SUB1A-1-regulated stresses.
Hsing-Yi Cho, Mei-Yeh Jade Lu and Ming-Che Shih* (2018) New Phytologist https://doi.org/10.1111/nph.15589
Cellular responses to oxygen deprivation are essential for survival during energy crises in plants and animals. Hypoxia caused by submergence results in reprogramming of translation dynamic in plants, but the molecular mechanisms are not well understood. In Arabidopsis, there are two eIFiso4G genes, eIFiso4G1 and eIFiso4G2, which belong to the eIF4G family. Both eIFiso4Gs were phosphorylated by SnRK1 under submergence. Interestingly, the eIFiso4G1 knockout mutant, but not the eIFiso4G2 mutant, became more sensitive to submergence, implying that eIFiso4G1 is involved in regulating submergence tolerance in Arabidopsis. In addition, comparison of RNA sequences in the polysome fraction and the RNAs immunoprecipitated by eIFiso4G1 from Col-0 and the SnRK1 and eIFiso4G1 mutants revealed that lack of eIFiso4G1 phosphorylation disrupts the translation of specific mRNAs under submergence. Taken together, our findings suggest that the SnRK1-eIFiso4G1 relay controls the translation of an array of genes under hypoxia, including core hypoxia response genes and genes related to stress response and biosynthetic process.
Chih-Cheng Chien, Mei-Yi Chou, Chun-Yi Chen & Ming-Che Shih* (2019) Analysis of genetic diversity of Xanthomonas oryzae pv. oryzae populations in Taiwan Scientific Reports (https://doi.org/10.1038/s41598-018-36575-x)
Rice bacterial blight caused by Xanthomonas oryzae pv. oryzae (Xoo) is a major rice disease. In Taiwan, the tropical indica type of Oryza sativa originally grown in this area is mix-cultivated with the temperate japonica type of O. sativa, and this might have led to adaptive changes of both rice host and Xoo isolates. In order to better understand how Xoo adapts to this unique environment, we collected and analyzed fifty-one Xoo isolates in Taiwan. Three different genetic marker systems consistently identified five groups. Among these groups, two of them had unique sequences in the last acquired ten spacers in the clustered regularly interspaced short palindromic repeats (CRISPR) region, and the other two had sequences that were similar to the Japanese isolate MAFF311018 and the Philippines isolate PXO563, respectively. The genomes of two Taiwanese isolates with unique CRISPR sequence features, XF89b and XM9, were further completely sequenced. Comparison of the genome sequences suggested that XF89b is phylogenetically close to MAFF311018, and XM9 is close to PXO563. Here, documentation of the diversity of groups of Xoo in Taiwan provides evidence of the populations from different sources and hitherto missing information regarding distribution of Xoo populations in East Asia.
Chung-Chih Yang, Cheng-Kuei Chang, Meng-Ting Chang, and Lie-Fen Shyur*(2018) Plant galactolipid dLGG suppresses lung metastasis of melanoma through deregulating TNF-α-mediated pulmonary vascular permeability and circulating oxylipin dynamics in mice. International Journal of Cancer,2018, 15;143(12):3248-3261. doi: 10.1002/ijc.31663.
This study demonstrates the pharmacological activity and the underlying molecular mechanisms of phytoagent dLGG isolated from medicinal plant Crassocephalum rabens (Asteraceae) on inhibition of melanoma cell EMT, tight junction permeability, and extravasation of melanoma cells in vivo that support the novel therapeutic effect of dLGG against melanoma lung metastasis. These study results are the important evidence to support the anti-cancer “Zhaohe Cao Botanical Drug” IND approval by US FDA. We investigated the in vivo dLGG effect against melanoma (B16COX-2/Luc) lung metastasis and cisplatin was used as the control drug. dLGG and cisplatin significantly inhibited melanoma lung metastasis and prolonged mean survival time of mice compared to the tumor control group. dLGG treatment inhibited proliferative and invasive activities of metastasized melanoma cells in mouse lung tissues, down-regulated the expression of proteins involved in epithelial-mesenchymal transition (vimentin, snail, TGF-β, and β-catenin), inhibited immune check point markers PD-1 and PD-L1, and macrophages and neutrophils infiltration, and promoted CD8+ Tc cells recruitment in mouse lung microenvironment. Oxylipins play a crucial role in mediating inflammation and carcinogenesis. Our LC/MS-based metabolomics study demonstrated that a 12-fold increase of circulating oxylipin 17-HDHA in mouse serum by dLGG treatment. We observed for the first time that 17-HDHA and dLGG inhibited B16 melanoma cells to secret TNF-α, subsequently inhibited the TNF-α-induced disruption of tight junction proteins (claudin/ZO2) expression in human umbilical endothelial cell monolayer. 17-HDHA and dLGG can down-regulate Src/pyk2 signal transduction pathway which is associated with tight junction proteins functions to maintain pulmonary epithelial structure integrity.
Lin, Y.-C., Wang, J., Delhomme, N., Schiffthaler, B., Sundström, G., Zuccolo, A., Nystedt, B., Hvidsten, T. R., de la Torre, A., Cossu, R. M., Hoeppner, M. P., Lantz, H., Scofield, D. G., Zamani, N., Johansson, A., Mannapperuma, C., Robinson, K. M., Mähler, N., Leitch, I. J., Pellicer, J., Park, E.-J., Van Montagu, M., Van de Peer, Y., Grabherr, M., Jansson, S., Ingvarsson, P. K. and Street, N. R. (2018) Functional and evolutionary genomic inferences in Populus through genome and population sequencing of American and European aspen. PNAS published ahead of print October 29, 2018
We performed de novo, full-genome sequence analysis of two Populus species, North American quaking and Eurasian trembling aspen, that contain striking levels of genetic variation. Our results showed that positive and negative selection broadly affects patterns of genomic variation, but to varying degrees across coding and noncoding regions. The strength of selection and rates of sequence divergence were strongly related to differences in gene expression and coexpression network connectivity. These results highlight the importance of both positive and negative selection in shaping genome-wide levels of genetic variation in an obligately outcrossing, perennial plant. The resources we present establish aspens as a powerful study system enabling future studies for understanding the genomic determinants of adaptive evolution. To maximize the community utility of these resources, we have integrated all presented data within the PopGenIE web resource (PopGenIE.org).
Lin W-Y, Lin Y-Y, Chiang S-F, Syu C, Hsieh L-C*, Chiou T-J* (2018) Evolution of microRNA827 targeting in the plant kingdom. New Phytologist 217: 1712-1725
Unlike most ancient microRNAs, which conservatively target homologous genes across species, microRNA827 (miR827) targets two different types of SPX (SYG1/PHO81/XPR1)-domain-containing genes, NITROGEN LIMITATION ADAPTATION (NLA) and PHOSPHATE TRANSPORTER 5 (PHT5), in Arabidopsis thaliana and Oryza sativa to regulate phosphate (Pi) transport and storage, respectively. However, how miR827 shifted its target preference and its evolutionary history are unknown. Based on target prediction analysis, we found that in most angiosperms, miR827 conservatively targets PHT5 homologs, but in Brassicaceae and Cleomaceae it preferentially targets NLA homologs, and we provide evidence for the transition of target preference during Brassicales evolution. Intriguingly, we found a lineage-specific loss of the miR827-regulatory module in legumes. Analysis of miR827-mediated cleavage efficiency and the expression of PHT5 in A. thaliana indicated that accumulation of mutations in the target site and the exclusion of the target site by alternative transcriptional initiation eliminated PHT5 targeting by miR827. * Here, we identified a transition of miR827 target preference during plant evolution and revealed the uniqueness of miR827-mediated regulation among conserved plant miRNAs. Despite the change in its target preference, upregulation of miR827 by Pi starvation and its role in regulating cellular Pi homeostasis were retained.
Leong, S. J., Lu, W.-C. and Chiou, T.-J.* (2018) Phosphite-Mediated Suppression of Anthocyanin Accumulation Regulated by Mitochondrial ATP Synthesis and Sugar in Arabidopsis. Plant & Cell Physiology 59: 1158-1169
Despite the essential role of phosphate (Pi) in plant growth and development, how plants sense and signal the change of Pi supply to adjust its uptake and utilization is not yet well understood. Pi itself has been proposed to be a signaling molecule that regulates Pi starvation responses (PSRs) because phosphite (Phi), a non-metabolized Pi analog, suppresses several PSRs. In this study, we identified a phosphite-insensitive1 (phi1) mutant which retained anthocyanin, a visible PSR, in Phi-containing but Pi-deficient medium. phi1 mutants were impaired in the gene encoding an FAd subunit of mitochondrial F1Fo-ATP synthase and showed a reduced mitochondrial ATP level in roots, growth hypersensitivity to oligomycin and an increased mitochondrial membrane potential, suggesting that this gene has a crucial role in mitochondrial ATP synthesis. phi1 mutants accumulated a high level of sugars in shoots, which may account for the increased accumulation of anthocyanin and starch in Phi-containing conditions. Gene expression analysis showed that a subset of genes involved in carbohydrate metabolism in phi1 was misregulated in response to Phi. The majority of genes were repressed by Pi starvation and, unlike wild-type plants, their repression in phi1 was not affected by the addition of Phi. Our findings show that defective mitochondrial ATP synthesis results in sugar accumulation, leading to alteration of Phi-mediated suppression of PSRs. This study reinforces the role of sugars, and also reveals a cross-talk among ATP, sugars and Pi/Phi molecules in mediating PSRs.
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2019/08/26 10:30 AM
Auditorium A134, Agricultural Technology Building 2019/09/09 10:30 AM
Dr. Michitaka Notaguchi (Associate Professor, Laboratory of Bioindustry, Bioscience and Biotechnology Center, Nagoya University & ITbM, Nagoya University, Japan)
Studies on grafting mechanism and a technique for graft production
Auditorium A134, Agricultural Technology Building