Molecular and Morphological Identification of Monilia yunnanensis Causing Brown Rot on Chinese Quince and Peach in Yunnan, China.

More than 30% of fruits of Chinese Quince (Chaenomeles speciosa) and peach (Prunus persica) showed circular, water-soaked and brown spots in July 2022 in Kunming, Yunnan, China. The center of these spots was covered by a large number of earthy brown and oblate sporogeneous mycelium containing conidiophore and conidia, which were one-celled, limoniform, hyaline (13.73 to 22.77 x 8.17 to 12.84 µm, n=50). By September 2022, almost 100% of fruits showed symptoms. Later, most of them fell or a few stiff, black and mummified fruits were left on the trees. Fungal isolates were isolated by single-spore technique on Potato Dextrose agar (PDA) from the diseased fruits, and incubated at room temperature (20-28 °C) in darkness for 14 days. The colony was gray, smooth at margins, 7.6-8.0 cm in diameter. To fullfill Koch's postulates, mycelial plugs of one representative isolate YHD611 from Chinese Quince and another YHD610 from peach were used to inoculate three wounded and three non-wounded surface-disinfected fruits of both hosts at room temperature (19-27 °C), respectively. Three wounded and three non-wounded fruits inoculated with sterile PDA plugs served as the control. The wounded peaches appeared water-soaked and had brown lesions after three days of inoculation, then completely decayed after nine days, while non-wounded fruits showed symptoms after five days. The wounded fruits of Chinese Quince developed similar symptoms after eight days of inoculation, and completely decayed after 13 days, while non-wounded fruits showed obvious symptoms after 15 days. In a subsequent study, isolate YHD611 was inoculated to peach while isolate YHD610 was inoculated to Chinese Quince to understand host specificity of the isolates. The results showed that when peaches were infected with YHD611, symptoms were observed on wounded fruits after three days while on non-wounded fruits after five days. When Chinese Quince was infected with YHD610, symptoms were observed on wounded fruits after 14 days while on non-wounded fruits after 21 days. Fungal isolates from symptomatic fruits were identical to the original isolates. There were no symptoms on the control fruits of both hosts. Molecular identification was confirmed based on the sequences of internal transcribed spacer (ITS, primers ITS1 and ITS4) and ß-tubulin (TUB2, primers Bt2a and Bt2b) genes (Niu et al. 2016). BLASTn analysis of the ITS (OQ15519and OQ155196) and TUB2 (OQ185202 and OQ185201) of YHD611 and YHD610 revealed a 100% sequence identity, respectively, to Monilia yunnanensis AH7-2 (KT735924.1 for ITS, KT736008.1 for TUB2). In the phylogenetic analyses based on ITS and TUB2 sequence data, the isolates YHD611 and YHD610 belonged to the M. yunnanensis clade. Based on morphological and molecular identification, both isolates were identified as M. yunnanensis, which was reported as the pathogen causing brown rot of plum, peach, apple and pear in Yunnan, China (Hu et al. 2011; Yin et al. 2015). To our knowledge, this is the first report of M. yunnanensis causing brown rot on the fruits of Chinese Quince in Yunnan, China. This study also reports that M. yunnanensis from Chinese Quince can infect peach, and the pathogen from peach can infect Chinese Quince. These findings suggest that M. yunnanensis can transfer from one host to another and causing serious economic losses in multiple fruit crops in Yunnan, China. References: Hu, M. J., et al. 2011. PLoS One. 6:e24990. Niu, C. W., et al. 2016. Mycosystema, 35(10):1. Yin, L. F., et al. 2015. Plant Dis. 99:1775.

Structural insights into the elevator-type transport mechanism of a bacterial ZIP metal transporter.

The Zrt-/Irt-like protein (ZIP) family consists of ubiquitously expressed divalent metal transporters critically involved in maintaining systemic and cellular homeostasis of zinc, iron, and manganese. Here, we present a study on a prokaryotic ZIP from Bordetella bronchiseptica (BbZIP) by combining structural biology, evolutionary covariance, computational modeling, and a variety of biochemical assays to tackle the issue of the transport mechanism which has not been established for the ZIP family. The apo state structure in an inward-facing conformation revealed a disassembled transport site, altered inter-helical interactions, and importantly, a rigid body movement of a 4-transmembrane helix (TM) bundle relative to the other TMs. The computationally generated and biochemically validated outward-facing conformation model revealed a slide of the 4-TM bundle, which carries the transport site(s), by approximately 8 Å toward the extracellular side against the static TMs which mediate dimerization. These findings allow us to conclude that BbZIP is an elevator-type transporter.

History, mechanism of action, and toxicity: a review of commonly used dough rheology improvers.

Dough rheology improvers, which often are oxidative reagents in nature, have long been used in bread-making industry to enhance protein crosslinking and subsequently improve the dough rheological properties and bread qualities. Numerous studies were conducted to explore the effects of these oxidative agents on dough quality improving, however, the underlying mechanism of their action during dough development has not been fully understood. Due to the public health concerns, multiple oxidative reagents were banned in some countries across the world, while others are still permitted in accordance with regulations. Therefore, a comprehensive understanding of their application, significance, and safety in bread manufacturing is necessary. This review aims to provide a detailed information about the evolutionary history of several commonly used oxidants acting as dough rheology improvers, their mechanisms of action, as well as their potential toxicity.

Effect of Muscle Fatigue on Surface Electromyography-Based Hand Grasp Force Estimation.

Surface electromyography- (sEMG-) based hand grasp force estimation plays an important role with a promising accuracy in a laboratory environment, yet hardly clinically applicable because of physiological changes and other factors. One of the critical factors is the muscle fatigue concomitant with daily activities which degrades the accuracy and reliability of force estimation from sEMG signals. Conventional qualitative measurements of muscle fatigue contribute to an improved force estimation model with limited progress. This paper proposes an easy-to-implement method to evaluate the muscle fatigue quantitatively and demonstrates that the proposed metrics can have a substantial impact on improving the performance of hand grasp force estimation. Specifically, the reduction in the maximal capacity to generate force is used as the metric of muscle fatigue in combination with a back-propagation neural network (BPNN) is adopted to build a sEMG-hand grasp force estimation model. Experiments are conducted in the three cases: (1) pooling training data from all muscle fatigue states with time-domain feature only, (2) employing frequency domain feature for expression of muscle fatigue information based on case 1, and 3) incorporating the quantitative metric of muscle fatigue value as an additional input for estimation model based on case 1. The results show that the degree of muscle fatigue and task intensity can be easily distinguished, and the additional input of muscle fatigue in BPNN greatly improves the performance of hand grasp force estimation, which is reflected by the 6.3797% increase in R2 (coefficient of determination) value.

The wPDI Redox Cycle Coupled Conformational Change of the Repetitive Domain of the HMW-GS 1Dx5-A Computational Study.

The repetitive sequence of glutenin plays an important role in dough rheology; however, its interaction with wheat protein disulfide isomerase (wPDI) remains unclear. In this study, the conformations of wild type glutenin repetitive sequence (WRS) from the high molecular weight glutenin subunit (HMW-GS) 1Dx5, an artificially designed glutenin repetitive sequence (DRS) of which the amino acid composition is the same but the primary structure is different, and wPDI under different redox states were simulated. The molecular interactions between the aforementioned repetitive sequences with wPDI under different redox states were further investigated. The results indicated that the repetitive sequences bind to the b and b' domains of an "open", oxidized wPDI (wPDIO) which serves as the acceptor state of substrate. The repetitive sequence is partially folded (compressed) in wPDIO, and is further folded in the thermodynamically favored, subsequent conformational transition of wPDIO to reduced wPDI (wPDIR). Compared with the artificially designed one, the naturally designed repetitive sequence is better recognized and more intensively folded by wPDI for its later unfold as the molecular basis of dough extension.

Curdlan conformation change during its hydrolysis by multi-domain ß-1,3-glucanases.

Enzymatic curdlan hydrolysis is gaining more attention for the value of oligo-ß-glucans in many aspects. Currently, the triple-helical conformation of curdlan fiber was imposed to the structure of ß-1,3-glucanase as its substrate without experimental evidence. Here, solution conformation of differently treated curdlan and each hydrolysis rate by a variety of ß-1,3-glucanases were systematically examined. Results showed that different enzymes exhibited preferences over the trajectories of pH change that curdlan solution went through, and all enzymes hydrolyzed heat treated curdlan solution at their maximum rates where most of the higher ordered helices were diminished. Combined with molecular docking studies, a multi-step hydrolysis process was proposed. Recognition of triple-helical curdlan by their ancillary region of ß-1,3-glucanase occurred before its unwinding into single- and double-helical forms, and the later ones fitted better to the catalytic cavity of the enzyme where the polysaccharides chain eventually got hydrolyzed into oligo-ß-glucans.