Diploid mycelia of Ustilago esculenta fails to maintain sustainable proliferation in host plant.

Smut fungi display a uniform life cycle including two phases: a saprophytic phase in vitro and a parasitic phase in host plants. Several apathogenic smut fungi are found, lacking suitable hosts in their habitat. Interestingly, MT-type Ustilago esculenta was found to maintain a parasitic life, lacking the saprophytic phase. Its long period of asexual proliferation in plant tissue results in severe defects in certain functions. In this study, the growth dynamics of U. esculenta in plant tissues were carefully observed. The mycelia of T- and MT-type U. esculenta exhibit rapid growth after karyogamy and aggregate between cells. While T-type U. esculenta successfully forms teliospores after aggregation, the aggregated mycelia of MT-type U. esculenta gradually disappeared after a short period of massive proliferation. It may be resulted by the lack of nutrition such as glucose and sucrose. After overwintering, infected Zizania latifolia plants no longer contained diploid mycelia resulting from karyogamy. This indicated that diploid mycelia failed to survive in plant tissues. It seems that diploid mycelium only serves to generate teliospores. Notably, MT-type U. esculenta keeps the normal function of karyogamy, though it is not necessary for its asexual life in plant tissue. Further investigations are required to uncover the underlying mechanism, which would improve our understanding of the life cycle of smut fungi and help the breeding of Z. latifolia.

Photopatternable and Highly Conductive PEDOT:PSS Electrodes for Flexible Perovskite Light-Emitting Diodes.

Flexible perovskite light-emitting diodes (PeLEDs) constitute an emerging technology opening new opportunities in the fields of lighting and display for portable and wearable electronics. Poly(3,4-ethylenedioxythiophene):poly(stryrenesulfonate) (PEDOT:PSS) as one of the most promising flexible electrode materials has attracted extensive attention. However, the patterning and conductivity issues of PEDOT:PSS electrodes should be addressed primarily. Here, a photopolymerizable additive is proposed to endow the PEDOT:PSS electrodes with photopatternability. Moreover, this additive can also improve the conductivity of the PEDOT:PSS electrode from 0.16 to 627 S/cm because of the phase separation between PEDOT and PSS components and conformation transition of PEDOT chains. Eventually, highly conductive PEDOT:PSS electrodes with various patterns are applied in flexible PeLEDs, demonstrating a high luminance of 25972 cd/m2 and a current efficiency of 25.1 cd/A. This work provides a facile and effective method of patterning and improving the conductivity of PEDOT:PSS electrodes simultaneously, demonstrating the great potential of PEDOT:PSS electrodes in flexible perovskite optoelectronics.

Multidentate Zwitterionic Ligand-Assisted Formation of Pure Bromide-Based Perovskite Nanosheets and Their Application in Blue Light-Emitting Diodes.

Perovskite light-emitting diodes (PeLEDs) have demonstrated rapid development during the past decade, whereas the inferior device performance of blue ones impedes the application in full-color display and lighting. Low-dimensional perovskites turn out to be the most promising blue-emitters owing to their superior stability. In this work, a multidentate zwitterionic l-arginine is proposed to achieve blue emission from pure bromide-based perovskites by in situ-forming low-dimensional nanosheets. First, l-arginine can promote the formation of perovskite nanosheets due to the strong interaction between the peripheral guanidinium cations and [PbBr6]4- octahedral layers, enabling a significant blue-shift. Second, the carboxyl group within l-arginine can passivate uncoordinated Pb2+ ions, improving the device performance. Finally, a blue PeLED is successfully constructed on the basis of the l-arginine-modulated perovskite film, demonstrating a peak luminance of 2152 cd/m2, an external quantum efficiency of 5.4%, and operation lifetime of 13.81 min. Further, the enlightenment from this work is hopefully to be applied in rationally designing spacer cations for low-dimensional perovskite optoelectronic devices.

An Endoglucanase Secreted by Ustilago esculenta Promotes Fungal Proliferation.

Ustilago esculenta is a fungus of two morphological forms, among the filamentous dikaryon that can induce the plant stem to expand to form fleshy stem. In order to establish biotrophy with Zizania latifolia which belongs to the tribe Oryzeae (Poaceae), U. esculenta firstly needs to secrete a bunch of effectors, among them being cell wall degrading enzymes (CWDEs). We have isolated a gene, UeEgl1, which was differentially expressed in MT-type and T-type U. esculenta at an early stage of infection, and specifically induced in the filamentous growth of the T-type. Bioinformatics analysis and enzyme activity assay indicated that UeEgl1 functions outside the cell as a ß-1,4-endoglucanase with a conserved domain of the glycosyl hydrolase family 45 (GH45) which targets the main component of the plant cell wall ß-1,4 linked glycosidic bonds. The phenotype analysis of UeEgl1 deletion mutants and UeEgl1 over-expression transformants showed that UeEgl1 had no significant effect on the budding, cell fusion, and filamentous growth of U. esculenta in vitro. Further study found that over-expression of UeEgl1 promoted the proliferation of mycelia inside Z. latifolia, and raised plant defense responses. The above results show that the UeEgl1 gene may play an important role in the early stage of infection through the decomposition of the plant cell wall.

Transcriptome Comparison between Two Strains of Ustilago esculenta during the Mating.

Ustilago esculenta is a smut fungus that obligately infects Zizania latifolia and stimulates tissue swelling to form galls. Unlike T-type, MT-type U. esculenta can only proliferate within plant tissues and infect the offspring of their host. Production of telispores, haploid life, and plant cuticle penetration are not essential for it, which may lead to the degeneration in these processes. Transcriptome changes during the mating of T- and MT-type U. esculenta were studied. The functions of several secreted proteins were further confirmed by knock-out mutants. Our results showed that MT-type U. esculenta can receive environmental signals in mating and circumstance sensing as T-type does. However, MT-type U. esculenta takes a longer time for conjunction tube formation and cytoplasmic fusion. A large number of genes encoding secreted proteins are enriched in the purple co-expression module. They are significantly up-regulated in the late stage of mating in T-type U. esculenta, indicating their relationship with infecting. The knock-out of g6161 (xylanase) resulted in an attenuated symptom. The knock-out of g943 or g4344 (function unidentified) completely blocked the infection at an early stage. This study provides a comprehensive comparison between T- and MT-type during mating and identifies two candidate effectors for further study.