Browsing by Subject "Plant Leaves"
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Item Open Access A plant genetic network for preventing dysbiosis in the phyllosphere.(Nature, 2020-04-08) Chen, Tao; Nomura, Kinya; Wang, Xiaolin; Sohrabi, Reza; Xu, Jin; Yao, Lingya; Paasch, Bradley C; Ma, Li; Kremer, James; Cheng, Yuti; Zhang, Li; Wang, Nian; Wang, Ertao; Xin, Xiu-Fang; He, Sheng YangThe aboveground parts of terrestrial plants, collectively called the phyllosphere, have a key role in the global balance of atmospheric carbon dioxide and oxygen. The phyllosphere represents one of the most abundant habitats for microbiota colonization. Whether and how plants control phyllosphere microbiota to ensure plant health is not well understood. Here we show that the Arabidopsis quadruple mutant (min7 fls2 efr cerk1; hereafter, mfec)1, simultaneously defective in pattern-triggered immunity and the MIN7 vesicle-trafficking pathway, or a constitutively activated cell death1 (cad1) mutant, carrying a S205F mutation in a membrane-attack-complex/perforin (MACPF)-domain protein, harbour altered endophytic phyllosphere microbiota and display leaf-tissue damage associated with dysbiosis. The Shannon diversity index and the relative abundance of Firmicutes were markedly reduced, whereas Proteobacteria were enriched in the mfec and cad1S205F mutants, bearing cross-kingdom resemblance to some aspects of the dysbiosis that occurs in human inflammatory bowel disease. Bacterial community transplantation experiments demonstrated a causal role of a properly assembled leaf bacterial community in phyllosphere health. Pattern-triggered immune signalling, MIN7 and CAD1 are found in major land plant lineages and are probably key components of a genetic network through which terrestrial plants control the level and nurture the diversity of endophytic phyllosphere microbiota for survival and health in a microorganism-rich environment.Item Open Access Contingency in ecosystem but not plant community response to multiple global change factors(New Phytologist, 2012) Bradford, MA; Wood, SA; Maestre, FT; REYNOLDS, JF; Warren, RJCommunity and ecosystem responses to global environmental change are contingent on the magnitude of change and interacting global change factors. To reveal whether responses are also contingent on the magnitude of each interacting factor, multifactor, multilevel experiments are required, but are rarely conducted. We exposed model grassland ecosystems to six levels of atmospheric CO2 and six levels of nitrogen enrichment, applying the latter both chronically (simulating deposition) and acutely (simulating fertilization). The 66 treatments were maintained for 6 months under controlled growing conditions, with biomass harvested every 28 d and sorted to species. Aboveground plant productivity responses to CO2 were contingent on nitrogen amount, and the responses to nitrogen amount were dependent on whether applications were chronic or acute. Specifically, productivity responses to increasing CO2 concentrations were accentuated with higher nitrogen enrichments, and productivity was greater when higher nitrogen enrichments were applied acutely. Plant community composition was influenced only by nitrogen enrichment, where the co-dominant grass species with the greatest leaf trait plasticity increasingly dominated with higher nitrogen amounts. Community processes are considered to be unpredictable, but our data suggest that the prediction of the impacts of simultaneous global changes is more complex for ecosystem processes, given that their responses are contingent on the levels of interacting factors.Item Open Access Dual transcriptomic analysis reveals metabolic changes associated with differential persistence of human pathogenic bacteria in leaves of Arabidopsis and lettuce.(G3 (Bethesda, Md.), 2021-12) Jacob, Cristián; Velásquez, André C; Josh, Nikhil A; Settles, Matthew; He, Sheng Yang; Melotto, MaeliUnderstanding the molecular determinants underlying the interaction between the leaf and human pathogenic bacteria is key to provide the foundation to develop science-based strategies to prevent or decrease the pathogen contamination of leafy greens. In this study, we conducted a dual RNA-sequencing analysis to simultaneously define changes in the transcriptomic profiles of the plant and the bacterium when they come in contact. We used an economically relevant vegetable crop, lettuce (Lactuca sativa L. cultivar Salinas), and a model plant, Arabidopsis thaliana Col-0, as well as two pathogenic bacterial strains that cause disease outbreaks associated with fresh produce, Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium 14028s (STm 14028s). We observed commonalities and specificities in the modulation of biological processes between Arabidopsis and lettuce and between O157:H7 and STm 14028s during early stages of the interaction. We detected a larger alteration of gene expression at the whole transcriptome level in lettuce and Arabidopsis at 24 h post inoculation with STm 14028s compared to that with O157:H7. In addition, bacterial transcriptomic adjustments were substantially larger in Arabidopsis than in lettuce. Bacterial transcriptome was affected at a larger extent in the first 4 h compared to the subsequent 20 h after inoculation. Overall, we gained valuable knowledge about the responses and counter-responses of both bacterial pathogen and plant host when these bacteria are residing in the leaf intercellular space. These findings and the public genomic resources generated in this study are valuable for additional data mining.Item Open Access Evolution of leaf form in marsileaceous ferns: evidence for heterochrony.(Evolution; international journal of organic evolution, 2009-02) Pryer, KM; Hearn, DJUsing an explicit phylogenetic framework, ontogenetic patterns of leaf form are compared among the three genera of marsileaceous ferns (Marsilea, Regnellidium, and Pilularia) with the outgroup Asplenium to address the hypothesis that heterochrony played a role in their evolution. We performed a Fourier analysis on a developmental sequence of leaves from individuals of these genera. Principal components analysis of the harmonic coefficients was used to characterize the ontogenetic trajectories of leaf form in a smaller dimensional space. Results of this study suggest that the "evolutionary juvenilization" observed in these leaf sequences is best described using a mixed model of heterochrony (accelerated growth rate and early termination at a simplified leaf form). The later stages of the ancestral, more complex, ontogenetic pattern were lost in Marsileaceae, giving rise to the simplified adult leaves of Marsilea, Regnellidium, and Pilularia. Life-history traits such as ephemeral and uncertain habitats, high reproductive rates, and accelerated maturation, which are typical for marsileaceous ferns, suggest that they may be "r strategists." The evidence for heterochrony presented here illustrates that it has resulted in profound ecological and morphological consequences for the entire life history of Marsileaceae.Item Open Access Hydraulic redistribution of soil water by roots affects whole-stand evapotranspiration and net ecosystem carbon exchange.(New Phytol, 2010-07) Domec, Jean-Christophe; King, John S; Noormets, Asko; Treasure, Emrys; Gavazzi, Michael J; Sun, Ge; McNulty, Steven G*Hydraulic redistribution (HR) of water via roots from moist to drier portions of the soil occurs in many ecosystems, potentially influencing both water use and carbon assimilation. *By measuring soil water content, sap flow and eddy covariance, we investigated the temporal variability of HR in a loblolly pine (Pinus taeda) plantation during months of normal and below-normal precipitation, and examined its effects on tree transpiration, ecosystem water use and carbon exchange. *The occurrence of HR was explained by courses of reverse flow through roots. As the drought progressed, HR maintained soil moisture above 0.15 cm(3) cm(-3) and increased transpiration by 30-50%. HR accounted for 15-25% of measured total site water depletion seasonally, peaking at 1.05 mm d(-1). The understory species depended on water redistributed by the deep-rooted overstory pine trees for their early summer water supply. Modeling carbon flux showed that in the absence of HR, gross ecosystem productivity and net ecosystem exchange could be reduced by 750 and 400 g C m(-2) yr(-1), respectively. *Hydraulic redistribution mitigated the effects of soil drying on understory and stand evapotranspiration and had important implications for net primary productivity by maintaining this whole ecosystem as a carbon sink.Item Open Access Intake, digestibility, and passage of a commercially designed diet by two Propithecus species.(Am J Primatol, 1999) Campbell, JL; Eisemann, JH; Glander, KE; Crissey, SDThe digestibility and passage of an experimental diet was used to compare the digestive physiology of two Propithecus species: P. verreauxi and P. tattersalli. Though both animals have a similar feeding ecology, the captive status of P. verreauxi is considered more stable than that of P. tattersalli. The test diet included a local tree species, Rhus copallina, at 15% of dry matter intake (DMI) and Mazuri Leafeater Primate Diet at 85% of DMI. The chemical composition of the diet (dry matter basis) was 25% crude protein, 34% neutral detergent fiber (NDF), and 22% acid detergent fiber (ADF) with a gross energy of 4.52 kcal/g. After a 6 week acclimation to the experimental diet, animals were placed in research caging. After a 7 day adjustment period, animals were dosed with chromium mordant and Co-EDTA as markers for digesta passage and all feed refusals and feces were collected at timed intervals for 7 days. Digestibility values, similar for both species, were approximately 65% for dry matter, crude protein, and energy, and 40% and 35% respectively, for NDF and ADF. Transit times (17-18.5 hr) and mean retention times (31-34 hr) were not significantly different between species, and there was no difference between the chromium mordant and Co-EDTA. Serum values for glucose, urea, and non-esterified fatty acids (NEFA) were obtained during four different time periods to monitor nutritional status. While there was no change in serum glucose, serum urea increased over time. The NEFAs increased across all four time periods for P. verreauxi and increased for the first three periods then decreased in the last period for P. tattersalli. Results obtained indicate no difference in digestibility nor digesta passage between species, and that both Propithecus species were similar to other post-gastric folivores.Item Open Access Is there foul play in the leaf pocket? The metagenome of floating fern Azolla reveals endophytes that do not fix N2 but may denitrify.(The New phytologist, 2018-01) Dijkhuizen, LW; Brouwer, P; Bolhuis, H; Reichart, G; Koppers, N; Huettel, B; Bolger, AM; Li, F; Cheng, S; Liu, XDinitrogen fixation by Nostoc azollae residing in specialized leaf pockets supports prolific growth of the floating fern Azolla filiculoides. To evaluate contributions by further microorganisms, the A. filiculoides microbiome and nitrogen metabolism in bacteria persistently associated with Azolla ferns were characterized. A metagenomic approach was taken complemented by detection of N2 O released and nitrogen isotope determinations of fern biomass. Ribosomal RNA genes in sequenced DNA of natural ferns, their enriched leaf pockets and water filtrate from the surrounding ditch established that bacteria of A. filiculoides differed entirely from surrounding water and revealed species of the order Rhizobiales. Analyses of seven cultivated Azolla species confirmed persistent association with Rhizobiales. Two distinct nearly full-length Rhizobiales genomes were identified in leaf-pocket-enriched samples from ditch grown A. filiculoides. Their annotation revealed genes for denitrification but not N2 -fixation. 15 N2 incorporation was active in ferns with N. azollae but not in ferns without. N2 O was not detectably released from surface-sterilized ferns with the Rhizobiales. N2 -fixing N. azollae, we conclude, dominated the microbiome of Azolla ferns. The persistent but less abundant heterotrophic Rhizobiales bacteria possibly contributed to lowering O2 levels in leaf pockets but did not release detectable amounts of the strong greenhouse gas N2 O.Item Open Access Localization of DIR1 at the tissue, cellular and subcellular levels during Systemic Acquired Resistance in Arabidopsis using DIR1:GUS and DIR1:EGFP reporters.(BMC plant biology, 2011-01) Champigny, Marc J; Shearer, Heather; Mohammad, Asif; Haines, Karen; Neumann, Melody; Thilmony, Roger; He, Sheng Yang; Fobert, Pierre; Dengler, Nancy; Cameron, Robin KBACKGROUND: Systemic Acquired Resistance (SAR) is an induced resistance response to pathogens, characterized by the translocation of a long-distance signal from induced leaves to distant tissues to prime them for increased resistance to future infection. DEFECTIVE in INDUCED RESISTANCE 1 (DIR1) has been hypothesized to chaperone a small signaling molecule to distant tissues during SAR in Arabidopsis. RESULTS: DIR1 promoter:DIR1-GUS/dir1-1 lines were constructed to examine DIR1 expression. DIR1 is expressed in seedlings, flowers and ubiquitously in untreated or mock-inoculated mature leaf cells, including phloem sieve elements and companion cells. Inoculation of leaves with SAR-inducing avirulent or virulent Pseudomonas syringae pv tomato (Pst) resulted in Type III Secretion System-dependent suppression of DIR1 expression in leaf cells. Transient expression of fluorescent fusion proteins in tobacco and intercellular washing fluid experiments indicated that DIR1's ER signal sequence targets it for secretion to the cell wall. However, DIR1 expressed without a signal sequence rescued the dir1-1 SAR defect, suggesting that a cytosolic pool of DIR1 is important for the SAR response. CONCLUSIONS: Although expression of DIR1 decreases during SAR induction, the protein localizes to all living cell types of the vasculature, including companion cells and sieve elements, and therefore DIR1 is well situated to participate in long-distance signaling during SAR.Item Open Access Mechanical defenses in leaves eaten by Costa Rican howling monkeys (Alouatta palliata).(Am J Phys Anthropol, 2006-01) Glander, Kenneth Earl; Lucas, PW; Teaford, Mark F; Ungar, PSPrimate species often eat foods of different physical properties. This may have implications for tooth structure and wear in those species. The purpose of this study was to examine the mechanical defenses of leaves eaten by Alouatta palliata from different social groups at Hacienda La Pacifica in Costa Rica. Leaves were sampled from the home-ranges of groups living in different microhabitats. Specimens were collected during the wet and dry seasons from the same tree, same plant part, and same degree of development as those eaten by the monkeys. The toughness of over 300 leaves was estimated using a scissors test on a Darvell mechanical tester. Toughness values were compared between social groups, seasons, and locations on the leaves using ANOVA. Representative samples of leaves were also sun-dried for subsequent scanning electron microscopy and energy dispersive x-ray (EDX) analyses in an attempt to locate silica on the leaves. Both forms of mechanical defense (toughness and silica) were found to be at work in the plants at La Pacifica. Fracture toughness varied significantly by location within single leaves, indicating that measures of fracture toughness must be standardized by location on food items. Monkeys made some food choices based on fracture toughness by avoiding the toughest parts of leaves and consuming the least tough portions. Intergroup and seasonal differences in the toughness of foods suggest that subtle differences in resource availability can have a significant impact on diet and feeding in Alouatta palliata. Intergroup differences in the incidence of silica on leaves raise the possibility of matching differences in the rates and patterns of tooth wear.Item Open Access Mechanical defenses in leaves eaten by Costa Rican howling monkeys (Alouatta palliata).(Am J Phys Anthropol, 2006-01) Teaford, MF; Lucas, PW; Ungar, PS; Glander, KEPrimate species often eat foods of different physical properties. This may have implications for tooth structure and wear in those species. The purpose of this study was to examine the mechanical defenses of leaves eaten by Alouatta palliata from different social groups at Hacienda La Pacifica in Costa Rica. Leaves were sampled from the home-ranges of groups living in different microhabitats. Specimens were collected during the wet and dry seasons from the same tree, same plant part, and same degree of development as those eaten by the monkeys. The toughness of over 300 leaves was estimated using a scissors test on a Darvell mechanical tester. Toughness values were compared between social groups, seasons, and locations on the leaves using ANOVA. Representative samples of leaves were also sun-dried for subsequent scanning electron microscopy and energy dispersive x-ray (EDX) analyses in an attempt to locate silica on the leaves. Both forms of mechanical defense (toughness and silica) were found to be at work in the plants at La Pacifica. Fracture toughness varied significantly by location within single leaves, indicating that measures of fracture toughness must be standardized by location on food items. Monkeys made some food choices based on fracture toughness by avoiding the toughest parts of leaves and consuming the least tough portions. Intergroup and seasonal differences in the toughness of foods suggest that subtle differences in resource availability can have a significant impact on diet and feeding in Alouatta palliata. Intergroup differences in the incidence of silica on leaves raise the possibility of matching differences in the rates and patterns of tooth wear.Item Open Access Regulation of growth-defense balance by the JASMONATE ZIM-DOMAIN (JAZ)-MYC transcriptional module.(The New phytologist, 2017-09) Major, Ian T; Yoshida, Yuki; Campos, Marcelo L; Kapali, George; Xin, Xiu-Fang; Sugimoto, Koichi; de Oliveira Ferreira, Dalton; He, Sheng Yang; Howe, Gregg AThe plant hormone jasmonate (JA) promotes the degradation of JASMONATE ZIM-DOMAIN (JAZ) proteins to relieve repression on diverse transcription factors (TFs) that execute JA responses. However, little is known about how combinatorial complexity among JAZ-TF interactions maintains control over myriad aspects of growth, development, reproduction, and immunity. We used loss-of-function mutations to define epistatic interactions within the core JA signaling pathway and to investigate the contribution of MYC TFs to JA responses in Arabidopsis thaliana. Constitutive JA signaling in a jaz quintuple mutant (jazQ) was largely eliminated by mutations that block JA synthesis or perception. Comparison of jazQ and a jazQ myc2 myc3 myc4 octuple mutant validated known functions of MYC2/3/4 in root growth, chlorophyll degradation, and susceptibility to the pathogen Pseudomonas syringae. We found that MYC TFs also control both the enhanced resistance of jazQ leaves to insect herbivory and restricted leaf growth of jazQ. Epistatic transcriptional profiles mirrored these phenotypes and further showed that triterpenoid biosynthetic and glucosinolate catabolic genes are up-regulated in jazQ independently of MYC TFs. Our study highlights the utility of genetic epistasis to unravel the complexities of JAZ-TF interactions and demonstrates that MYC TFs exert master control over a JAZ-repressible transcriptional hierarchy that governs growth-defense balance.Item Open Access Two new endophytic Atractiellomycetes, Atractidochium hillariae and Proceropycnis hameedii.(Mycologia, 2018-01) Aime, M Catherine; Urbina, Hector; Liber, Julian A; Bonito, Gregory; Oono, RyokoSterile fungal isolates are often recovered in leaf and root endophytic studies, although these seldom play a significant role in downstream analyses. The authors sought to identify and characterize two such endophytes-one representing the most commonly recovered fungal isolate in recent studies of needle endophytes of Pinus taeda and the other representing a rarely isolated root endophyte of Populus trichocarpa. Both are shown by DNA sequencing to be undescribed species of Atractiellomycetes (Pucciniomycotina, Basidiomycota), a poorly characterized class of mostly plant-associated and presumably saprobic microfungi. The authors describe the new genus and species Atractidochium hillariae (Phleogenaceae) and the new species Proceropycnis hameedii (Hoehnelomycetaceae), both in the Atractiellales, to accommodate these unusual isolates. Following incubations of 1-2 mo, A. hillariae produces minute white sporodochia, similar to those produced by several other members of Atractiellales, whereas Pr. hameedii forms conidia singly or in chains in a manner similar to its sister species Pr. pinicola. Additionally, we provide a taxonomic revision of Atractiellomycetes based on multilocus analyses and propose the new genera Neogloea (Helicogloeaceae) and Bourdotigloea (Phleogenaceae) to accommodate ex-Helicogloea species that are not congeneric with the type H. lagerheimii. Atractiellomycetes consists of a single order, Atractiellales, and three families, Hoehnelomycetaceae, Phleogenaceae, and Helicogloeaceae. Accumulated evidence suggests that Atractiellomycetes species are common but infrequently isolated members of plant foliar and root endobiomes.Item Open Access Variation in Plant Response to Herbivory Underscored by Functional Traits.(PLoS One, 2016) Reese, Aspen T; Ames, Gregory M; Wright, Justin PThe effects of herbivory can shape plant communities and evolution. However, the many forms of herbivory costs and the wide variation in herbivory pressure, including across latitudinal gradients, can make predicting the effects of herbivory on different plant species difficult. Functional trait approaches may aid in contextualizing and standardizing the assessment of herbivory impacts. Here we assessed the response of 26 old-field plant species to simulated defoliation in a greenhouse setting by measuring whole plant and leaf level traits in control and treated individuals. Simulated defoliation had no significant effects on any plant traits measured. However, the baseline leaf level traits of healthy plants consistently predicted the log response ratio for these species whole plant response to defoliation. The latitudinal mid-point of species' distributions was also significantly correlated with aboveground biomass and total leaf area responses, with plants with a more northern distribution being more negatively impacted by treatment. These results indicate that even in the absence of significant overall impacts, functional traits may aid in predicting variability in plant responses to defoliation and in identifying the underlying limitations driving those responses.