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Leaves are the key organs of plants that produce photosynthates. Leaf senescence aids nutrient remobilization from source to sink tissues, which dramatically affects crop quality and yield. Although several senescence-associated genes (SAGs) have been recognized in cotton, the function of lipoic acid synthase in leaf senescence remains unclear. Therefore, we isolated a lipoic acid synthase gene named GhLIP1 from cotton (Gossypium hirsutum L.). Protein domain analysis revealed that GhLIP1 had a LIAS-N domain and an Elp3 domain, and yeast mutant complementation experiments demonstrated that GhLIP1 was a lipoic acid synthase. GhLIP1 expression pattern analysis showed that GhLIP1 was vastly expressed in fibres, and the phytohormone IAA (indole-3-acetic acid) induced its transcription. When GhLIP1 was transformed into Arabidopsis, the leaves of overexpression Arabidopsis exhibited a late leaf senescence phenotype compared to wild-type Arabidopsis, Col-0. Moreover, downregulation of GhLIP1 expression using virus-induced gene silencing (VIGS) technology resulted in early leaf senescence in cotton. qRT-PCR analyses revealed that two SAGs, GhWRKY53 and GhNAP, were upregulated in cotton plants with GhLIP1 knock-down. Cell ultrastructure observations found that chloroplasts were degraded in an orderly manner in cotton leaf cells with GhLIP1 knock-down. These results suggest that GhLIP1 plays a significant role in leaf senescence in cotton.

Background Virus-induced gene silencing (VIGS) is one of the most convenient and powerful methods of reverse genetics. In vitro-inoculation of plant virus is an important method for studying the interactions between viruses and plants. Agrobacterium-based infiltration has been widely adopted as a tool for VIGS and in vitro-inoculation of plant virus. Most agrobacterium-based infiltration methods applied to VIGS and virus inoculation have the characteristics of low transformation efficiencies, long plant growth time, large amounts of plant tissue, large test spaces, and complex preparation procedures. Therefore, a rapid, simple, economical, and highly efficient VIGS and virus inoculation method is in need. Previous studies have shown that the selection of suitable plant tissues and inoculation sites is the key to successful infection. Results In this study, Tobacco rattle virus (TRV) mediated VIGS and Tomato yellow leaf curl virus (TYLCV) for virus inoculation were developed in tomato plants based on the agrobacterium tumefaciens-based infiltration by injection of the no-apical-bud stem section (INABS). The no-apical-bud stem section had a “Y- type” asymmetric structure and contained an axillary bud that was about 1–3 cm in length. This protocol provides high transformation (56.7%) and inoculation efficiency (68.3%), which generates VIGS transformants or diseased plants in a very short period (8 dpi). Moreover, it greatly reduces the required experimental space. This method will facilitate functional genomic studies and large-scale disease resistance screening. Conclusions Overall, a rapid, simple, and highly efficient method for VIGS and virus inoculation by INABS was developed in tomato. It was reasonable to believe that it can be used as a reference for the other virus inoculation methods and for the application of VIGS to other crops (such as sweet potato, potato, cassava and tobacco) that develop axillary buds and can survive from cuttings.

Background The commonly used NEMA IEC Body phantom has a number of defects, hindering its application for detecting micro-lesions and measuring the performance parameters of computed tomography (CT). This study aimed to propose a PET/CT phantom designed by National Institute of Metrology (NIM), China, which is capable of simultaneously testing the performance of PET and CT systems, and to evaluate the quality of imaging. Methods The phantom developed in the present study, the NIM PET/CT phantom, is composed of a PET imaging module and a CT imaging module, and these modules are connected together through bolts, which can simultaneously measure the imaging performance of PET and CT systems. Hot spheres were filled with 4:1 sphere-to-background activity concentration using 18F-fluorodeoxyglucose (18F-FDG), and cold spheres were filled with non-radioactive water. We compared the results of imaging obtained from the NIM PET/CT phantom and the NEMA IEC Body phantom to assess their diagnostic efficacy. In order to evaluate the generalization ability of the NIM PET/CT phantom, three different PET/CT systems were used to scan on the same scanning protocol. To evaluate the effects of image reconstruction algorithms on image quality assessment, ordered subset expectation maximization (OSEM), OSEM-point-spread function (PSF), OSEM-TOF, and OSEM-PSF-TOF algorithms were employed. Results The imaging quality of the NIM PET/CT phantom and the NEMA IEC Body phantom was relatively consistent. The NIM PET/CT phantom could detect 7 mm spheres without influencing the imaging quality. It was found that PSF reconstruction exhibited to reduce the speed of convergence, the contrast and background variability of spheres (13–28 mm) were significantly improved after two iterations. In addition to improve the image contrast and background variability, TOF could markedly improve the overall image quality and instrument detection limit. TOF-PSF could noticeably reduce noise level, enhance imaging details, and improve quality of imaging. Conclusions The results showed that in comparison with the NEMA IEC Body phantom, the NIM PET/CT phantom outperformed in evaluating the PET image quality of micro-lesions and the performance parameters of CT.

Pomegranate (Punica granatum L.) is an economically important fruit of the Punicaceae family and widely cultivated in the world. In 2019 and 2020, pomegranate fruits showing rot symptoms initiating from seed were observed in different pomegranate-cultivated fields in Henan province of China. Bacteria as a potential pathogen were isolated from the rot tissue of pomegranate seeds, and its pathogenicity was confirmed. The bacterium was identified as Bacillus altitudinis based on morphology and sequence analysis on the 16S ribosomal DNA and the gyrB gene. This is the first report on Bacillus altitudinis causing seed rot of pomegranate.

Autotoxicity is a serious problem for continuous cropping of cucumber, it can limit its own growth and that of nearby cucumber plants and decrease yield and quality. Cinnamic acid (CA) derivatives are a class of autotoxins that can mimic autotoxic effects in cucumber. We screened an Arabidopsis long hairpin RNA (lhRNA) library under CA-mimicked autotoxicity stress to obtain autotoxicity-resistant mutant lines. The glycerol-3-phosphate 2-O-acyltransferase 6 (GPAT6) gene was found to be silenced in one resistant mutant line, and GPAT6 homologous gene in cucumber was cloned and named CuGPAT6. To test gene function quickly, a new tobacco rattle virus (TRV)-mediated virus-induced gene silencing (VIGS) system was established in cucumber using a special agroinfiltration solution and whole cotyledonary nodes. Cucumber phytoene desaturase gene (CuPDS) and CuGPAT6 gene were successfully silenced with a newly established tobacco rattle virus (TRV)-mediated virus-induced gene silencing (VIGS) system in cucumber showing photobleaching and decreased CuPDS expression in leaves; and silencing of CuGPAT6 enhanced the tolerance to the autotoxin stress mimicked by CA in cucumber. It indicated that the alleviation of the damage caused by CA treatment was probably through maintaining the integrity of cellular structure, supporting cell vitality and promoting growth in roots, and increasing the integrate chloroplast and thylakoid numbers in leaves, which restored the growth and net photosynthesis rate of CA treated CuGPAT6 silenced plants to the similar level to those of control plants. The results also demonstrated that the newly established TRV mediated VIGS system is functional, rapid, convenient and highly efficient in cucumber.

For unacceptable computational efficiency and accuracy on the probabilistic analysis of multi-component system with multi-failure modes, this paper proposed multi-extremum response surface method (MERSM). MERSM model was established based on quadratic polynomial function by taking extremum response surface model as the sub-model of multi-response surface method. The dynamic probabilistic analysis of an aeroengine turbine blisk with two components, and their reliability of deformation and stress failures was obtained, based on thermal-structural coupling technique, by considering the nonlinearity of material parameters and the transients of gas flow, gas temperature and rotational speed. The results show that the comprehensive reliability of structure is 0.9904 when the allowable deformations and stresses of blade and disk are 4.78×10–3 m and 1.41×109 Pa, and 1.64×10–3 m and 1.04×109 Pa, respectively. Besides, gas temperature and rotating speed severely influence the comprehensive reliability of system. Through the comparison of methods, it is shown that the MERSM holds higher computational precision and speed in the probabilistic analysis of turbine blisk, and MERSM computational precision satisfies the requirement of engineering design. The efforts of this study address the difficulties on transients and multiple models coupling for the dynamic probabilistic analysis of multi-component system with multi-failure modes.