Growth of Arabidopsis seedlings on high fungal doses of Piriformospora indica has little effect on plant performance,stress, and defense gene expression in spite of elevated jasmonic acid and jasmonic acid-isoleucine levels in the roots

The endophytic fungus Piriformospora indica colonizes the roots of many plant species including Arabidopsis and promotes their performance, biomass, and seed production as well as resistance against biotic and abiotic stress. Imbalances in the symbiotic interaction such as uncontrolled fungal growth result in the loss of benefits for the plants and activation of defense responses against the microbe. We exposed Arabidopsis seedlings to a dense hyphal lawn of P. indica. The seedlings continue to grow, accumulate normal amounts of chlorophyll, and the photosynthetic parameters demonstrate that they perform well. In spite of high fungal doses around the roots, the fungal material inside the roots was not significantly higher when compared with roots that live in a beneficial symbiosis with P. indica. Fifteen defense- and stress-related genes including PR2, PR3, PAL2, and ERF1 are only moderately upregulated in the roots on the fungal lawn, and the seedlings did not accumulate H₂O₂/radical oxygen species. However, accumulation of anthocyanin in P. indica-exposed seedlings indicates stress symptoms. Furthermore, the jasmonic acid (JA) and jasmonic acid-isoleucine (JA-Ile) levels were increased in the roots, and consequently PDF1.2 and a newly characterized gene for a 2-oxoglurate and Fe²⁺-dependent oxygenase were upregulated more than 7-fold on the dense fungal lawn, in a JAR1- and EIN3-dependent manner. We conclude that growth of A. thaliana seedlings on high fungal doses of P. indica has little effect on the overall performance of the plants although elevated JA and JA-Ile levels in the roots induce a mild stress or defense response.     

Efficient in vitro regeneration systems for Vaccinium species

Efficient protocols for shoot regeneration from leaf explants suitable for micropropagation as well as for the development of transgenic plants were developed for blueberry (Vaccinium corymbosum) and lingonberry (Vaccinium vitis-idaea) cultivars. Nodal segments were used to initiate in vitro shoot cultures of lingonberry cultivar ‘Red Pearl’ and southern highbush blueberry cultivar ‘Ozarkblue’. In order to develop an optimized regeneration procedure, different types and concentrations of plant growth regulators were tested to induce adventitious shoot regeneration on excised leaves from micropropagated shoots of both cultivars. The effect on percentage regeneration and number of shoots per explant was investigated. Results indicated that zeatin was superior to TDZ and meta-topolin in promoting adventitious shoot formation. A concentration of 20 μM zeatin was most effective in promoting shoot regeneration in both cultivars, in case of ‘Red Pearl’ along with 1 μM NAA. Shoots were either allowed to root in vitro on medium containing IBA or NAA or ex vitro in a fog tunnel. IBA was superior to NAA for induction of root development in vitro in both Vaccinium cultivars. Ex vitro rooting under high humidity was tested with cuttings from mature field-grown plants, from acclimatized tissue culture derived plants and with unrooted in vitro proliferated shoots planted directly. It was found that in vitro shoots rooted better under fog than cuttings from the other plant sources and rooting was equivalent to that achieved in vitro.     

Aerobic spore-forming bacteria as detrimental infectants in plant tissue cultures

Summary Aerobic spore-forming bacteria were isolated from plant tissue cultures from a commercial plant cultivation station. Bacillus circulans was found to be a detrimental infectant as a serious consequence of the heat-resistance of the endospores of these bacteria. They were extremely motile, utilized several growth-promoting factors, and could be eliminated by early microscopical identification, killing by heat treatment, or by using antibiotics or disinfecants.Dedicated to Professor Dr. Gustav Kortüm on the occasion of his 80th birthday     

Ultrastructure of the plasmodial slime moldPerichaena vermicularis

Summary Mature plasmodia ofPerichaena vermicularis require a light period to induce sporulation. In this paper the ultrastructure and acid phosphatase localization of the mature plasmodium ofPerichaena vermicularis are investigated. Acid phosphatase is localized in vacuoles containing remnants of bacteria and cell organelles. Morphological and histochemical evidence support the interpretation that these vacuoles constitute two types of lysosomes called respectively heterophagic and autophagic vacuoles.Coated vesicles which apparently originate from smooth endoplasmic reticulum are dispersed throughout the plasmodium and frequently associated with lysosomes. Several dumbbellshaped mitochondria are observed in the plasmodium at the onset of fruiting but not during later stages of plasmodiocarp development. Cytoplasmic microtubules are identified inPerichaena vermicularis. Some of these are closely associated with microfilaments.This work was supported by National Science Foundation grants (GB-5884 and GB-8537) to Dr.Ian K.Ross, NSF grant (GB 12371) to Dr.James Cronshaw, and an NSF Traineeship (GZ 445 and 796) to I.Charvat.This constitutes a portion of a thesis presented to the Regents of the University of California by the first author in partial fulfillment of the requirements for the Ph. D. degree.     

Lineage sorting in multihost parasites: Eidmanniella albescens and Fregatiella aurifasciata on seabirds from the Galapagos Islands

Parasites comprise a significant percentage of the biodiversity of the planet and are useful systems to test evolutionary and ecological hypotheses. In this study, we analyze the effect of host species identity and the immediate local species assemblage within mixed species colonies of nesting seabirds on patterns of genetic clustering within two species of multihost ectoparasitic lice. We use three genetic markers (one mitochondrial, COI, and two nuclear, EF1‐α and wingless) and maximum likelihood phylogenetic trees to test whether (1) parasites show lineage sorting based on their host species; and (2) switching of lineages to the alternate host species depends on the immediate local species assemblage of individual hosts within a colony. Specifically, we examine the genetic structure of two louse species: Eidmanniella albescens, infecting both Nazca (Sula granti) and blue‐footed boobies (Sula nebouxii), and Fregatiella aurifasciata, infecting both great (Fregata minor) and magnificent frigatebirds (Fregata magnificens). We found that host species identity was the only factor explaining the patterns of genetic structure in both parasites. In both cases, there is evident genetic differentiation depending on the host species. Thus, a revision of the taxonomy of these louse species is needed. One possible explanation of this pattern is extremely low louse migration rates between host species, perhaps influenced by fine‐scale spatial separation of host species within mixed colonies, and low parasite infrapopulation numbers.     

Developmentally induced changes of the proteome in the protozoan parasite Leishmania donovani

In order to proceed through their life cycle, protozoan parasites of the genus Leishmania cycle between sandflies and mammals. This change of environment correlates with the differentiation from the promastigote stage (insect form) to the amastigote stage (intracellular mammalian form). The molecular basis underlying this major transformation is poorly understood so far; however, heat shock protein 90 (HSP90) appears to play a pivotal role. To further elucidate this process we identified proteins expressed preferentially in either of the two life cycle stages. By using two-dimensional (2-D) gel electrophoresis we observed defined changes in the protein pattern. A total of approximately 2000 protein spots were visualized. Of these, 31 proteins were present only in promastigotes. The abundance of 65 proteins increased during heat-induced in vitro amastigote differentiation, while a decreased abundance is observed for four proteins late in amastigote differentiation. Further analyses using matrix-assisted laser desorption/ionization-time of flight mass spectrometry and peptide mass fingerprinting 67 protein spots were identified representing 41 different proteins known from databases and eight hypothetical proteins. Further studies showed that most of the stage-specific proteins fall into five groups of functionally related proteins. These functional categories are: (i) stress response (e.g. heat, oxidative stress); (ii) cytoskeleton and cell membrane; (iii) energy metabolism and phosphorylation; (iv) cell cycle and proliferation; and (v) amino acid metabolism. Very similar changes in the 2-D protein pattern were obtained when in vitro amastigote differentiation was induced either by pharmacological inhibition of HSP90 or by a combination of heat stress and acidic pH supporting the critical role for HSP90 in life cycle control.     

A solution approach for deriving alternative fuel station infrastructure requirements

When an alternative fuel is introduced, the infrastructure through which that fuel is made available to the market is often underdeveloped. Transportation service providers relying on such infrastructures are unlikely to adopt alternative fuel vehicles as it may impose long detours for refueling. In this paper, we design and apply a new solution approach to derive minimum infrastructure requirements, in terms of the number of alternative fuel stations. The effectiveness of our approach is demonstrated by applying it to the case of introducing liquefied natural gas (LNG) as a transportation fuel in The Netherlands. From this case, we learn that, depending on the driving range of the LNG trucks and the size of area on which those trucks operate, a minimum of 5–12 LNG fuel stations is necessary to render LNG trucks economically and environmentally beneficial.     

The EF-Hand Ca2+ Binding Protein MICU Choreographs Mitochondrial Ca2+ Dynamics in Arabidopsis

Plant organelle function must constantly adjust to environmental conditions, which requires dynamic coordination. Ca²⁺ signaling may play a central role in this process. Free Ca²⁺ dynamics are tightly regulated and differ markedly between the cytosol, plastid stroma, and mitochondrial matrix. The mechanistic basis of compartment-specific Ca²⁺ dynamics is poorly understood. Here, we studied the function of At-MICU, an EF-hand protein of Arabidopsis thaliana with homology to constituents of the mitochondrial Ca²⁺ uniporter machinery in mammals. MICU binds Ca²⁺ and localizes to the mitochondria in Arabidopsis. In vivo imaging of roots expressing a genetically encoded Ca²⁺ sensor in the mitochondrial matrix revealed that lack of MICU increased resting concentrations of free Ca²⁺ in the matrix. Furthermore, Ca²⁺ elevations triggered by auxin and extracellular ATP occurred more rapidly and reached higher maximal concentrations in the mitochondria of micu mutants, whereas cytosolic Ca²⁺ signatures remained unchanged. These findings support the idea that a conserved uniporter system, with composition and regulation distinct from the mammalian machinery, mediates mitochondrial Ca²⁺ uptake in plants under in vivo conditions. They further suggest that MICU acts as a throttle that controls Ca²⁺ uptake by moderating influx, thereby shaping Ca²⁺ signatures in the matrix and preserving mitochondrial homeostasis. Our results open the door to genetic dissection of mitochondrial Ca²⁺ signaling in plants.