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Functional redundancy of Rpn5 in budding yeast allows its participation and function in two distinct but structurally related PCI complexes: the proteasome lid and the CSN. As a lid subunit, Rpn5 stabilizes proteasome integrity; as a CSN subunit, Rpn5 is required for enzymatic hydrolysis of Rub1/Nedd8 from cullins.

The plant hormone cytokinin (CK) is an important developmental regulator, promoting morphogenesis and delaying differentiation and senescence. From developmental processes, to growth, to stress tolerance, CKs are central in plant life. CKs are also known to mediate plant immunity and disease resistance, and several classes of microbes can also produce CKs, affecting the interaction with their plant hosts. While host species and genotype can be a driving force in shaping the plant microbiome, how plant developmental hormones such as CK can shape the microbiome is largely uninvestigated. Here, we examined the relationship between CK and the phyllosphere microbiome, finding that CK acts as a selective force in microbiome assembly, increasing richness, and promoting the presence of Firmicutes. CK-mediated immunity was found to partially depend on the microbial community, and bacilli isolated from previously described CK-rich plant genotypes, which overexpress a CK biosynthesis gene or have increased CK sensitivity, induced plant immunity, and promoted disease resistance. Using a biomimetic system, we investigated the relationship between the leaf microstructure, which is differentially patterned upon changes in CK content or signaling, and the growth of different phyllosphere microbes. We found that leaf structures derived from CK-rich plant genotypes support bacilli in the biomimetic system. CK was able to promote the growth, swarming, and biofilm formation of immunity inducing bacillus isolates in vitro. Overall, our results indicate that host genotype and hormonal profiles can act as a strong selective force in microbiome assembly, underlying differential immunity profiles, and pathogen resistance as a result.

Bacteria form interface-associated communities called biofilms, often comprising multiple species. Biofilms can be detrimental or beneficial in medical, industrial, and technological settings, and their stability and function are determined by interspecies communication via specific chemical signaling or metabolite exchange. The deterministic control of biofilm development, behavior, and properties remains an unmet challenge, limiting our ability to inhibit the formation of detrimental biofilms in biomedical settings and promote the growth of beneficial biofilms in biotechnology applications. Here, we describe the development of growth surfaces that promote the growth of commensal Escherichia coli instead of the opportunistic pathogen Pseudomonas aeruginosa. Periodically patterned growth surfaces induced robust morphological changes in surface-associated E. coli biofilms and influenced the antibiotic susceptibilities of E. coli and P. aeruginosa biofilms. Changes in the biofilm architecture resulted in the accumulation of a metabolite, indole, which controls the competition dynamics between the two species. Our results show that the surface on which a biofilm grows has important implications for species colonization, growth, and persistence when exposed to antibiotics.

Polydimethyl siloxane (PDMS) is the most widely used polymer in microfl uidic devices. Microfl uidic devices are used in all ranges of science. The microstructure of a microfl uidic device infl uences its effi ciency. One method for controlling microstructure is through wet etching. A particularly common etchant is tetrabutylammonium fl uoride (TBAF). This report shows that the etching rate of PDMS by a TBAF solution is controlled by the solvent in use. This report presents that solvent dictates interplay between the reactivity of the naked fl uoride with the Si O bonds in the polymer chain and the solubility of the polymer chains. Both high reactivity and accessibility are necessary for a high etching rate. This gives a simple method to control the etching rate of PDMS and by that the microstructure of the microfl uidic device.Dr. M. Kleiman, K. A. Ryu, Prof. A. P. Esser-Kahn Chemistry Department Natural Sciences II Irvine, CA 92697 , USA E-mail: aesserka@uci.edu One of the most common wet etchants for PDMS is tetrabutylammonium fl uoride (TBAF) [19][20][21] -owing to its rapid generation of "naked" fl uoride. Previously, researchers controlled the etching rate of PDMS by varying the fl ow rate and the concentration of TBAF. [ 22 ] They reported a maximum increase of 100% in etching rate by increasing fl ow rate as well as a structural change that depended on TBAF concentration. Here we show an increased etching rate of PDMS, up to two orders of magnitude, by changing the solvent. In these experiments, we use circular 3D channels and characterize the etching rate of the channels using TBAF dissolved in 16 common, organic solvents. Etching of PDMS by TBAF is currently thought to be mediated by the attack of the Si -O bonds of PDMS by the naked fl uoride. [23][24][25] The exact mechanism for the reaction between the naked fl uoride and the Si -O bonds remains unknown. From our current etching experiments, we demonstrate that the wide range of PDMS removal rates depends on two factors: (1) the reactivity of TBAF with Si -O bonds in the solvent, which in turn depends on the polarity of the solvent and (2) the degree of solvent swelling of PDMS.

The evolution of sex is one of the greatest mysteries in evolutionary biology. An even greater mystery is the evolution of obligate sex, particularly when competing with facultative sex and not with complete asexuality. Here, we develop a stochastic simulation of an obligate allele invading a facultative population, where males are subject to sexual selection. We identify a range of parameters where sexual selection can contribute to the evolution of obligate sex: Especially when the cost of sex is low, mutation rate is high, and the facultative individuals do not reproduce sexually very often. The advantage of obligate sex becomes larger in the absence of recombination. Surprisingly, obligate sex can take over even when the population has a lower mean fitness as a result. We show that this is due to the high success of obligate males that can compensate the cost of sex.

Soft rot disease caused by Pectobacterium spp. is responsible for severe agricultural losses in potato, vegetables, and ornamentals. The genus Zantedeschia includes two botanical groups of tuberous ornamental flowers that are highly susceptible to the disease. Previous studies revealed that Z. aethiopica, a member of the section Zantedeschia, is significantly more resistant to Pectobacterium spp. than members of the same genus that belong to the section Aestivae. During early infection, we found different patterns of bacterial colonization on leaves of hosts belonging to the different sections. Similar patterns of bacterial colonization were observed on polydimethylsiloxane (PDMS) artificial inert replicas of leaf surfaces. The replicas confirmed the physical effect of leaf texture, in addition to a biochemical plant–bacterium interaction. The differential patterns may be associated with the greater roughness of the abaxial leaf surfaces of Aestivae group that have evolutionarily adapted to mountainous environments, as compared to Zantedeschia group species that have adapted to warm, marshy environments. Transverse leaf sections also revealed compact aerenchyma and reduced the total volume of leaf tissue air spaces in Aestivae members. Finally, an analysis of defense marker genes revealed differential expression patterns in response to infection, with significantly higher levels of lipoxygenase 2 (lox2) and phenylalanine ammonia lyase (pal) observed in the more resistant Z. aethiopica, suggesting greater activation of induced systemic resistance (ISR) mechanisms in this group. The use of Zantedeschia as a model plant sheds light on how natural ecological adaptations may underlay resistance to bacterial soft rot in cultivated agricultural environments.