Heterogeneous Photocatalytic C(sp2)-H Activation of Formate for Hydrocarboxylation of Alkenes.

Light-driven carboxylation offers a promising approach for synthesizing valuable fine chemicals under mild conditions. Here we disclose a heterogeneous photocatalytic strategy of C(sp2)-H activation of formate for hydrocarboxylation of alkenes over zinc indium sulfide (ZnIn2S4) under visible light. This protocol functions well with a variety of substituted styrenes with good to excellent yields; it also works for unactivated alkenes albeit with lower yields. Mechanistic studies confirm the existence of CO2⋅- as a key intermediate. It was found that C(sp2)-H activation of formate is induced by S⋅ species on the surface of ZnIn2S4 via hydrogen atom transfer (HAT) instead of a photogenerated hole oxidation mechanism. Moreover, both cleavage of the C(sp2)-H of HCOO- and formation of a benzylic anion were found to be involved in the rate-determining step for the hydrocarboxylation of styrene.

Copper-decorated strategy based on defect-rich NH2-MIL-125(Ti) boosts efficient photocatalytic degradation of methyl mercaptan under sunlight.

Photocatalysis has received significant attention as a technology that can solve environmental problems. Metal-organic frameworks are currently being used as novel photocatalysts but are still limited by the rapid recombination of photogenerated carriers, low photogenerated electron migration efficiency and poor solar light utilization rate. In this work, a novel photocatalyst was successfully constructed by introducing Cu species into thermal activated mixed-ligand NH2-MIL-125 (Ti) via defect engineering strategy. The constructed defect structure not only provided 3D-interconnected gas transfer channels, but also offered suitable space to accommodate introduced Cu species. For the most effective photocatalyst 0.2Cu/80%NH2-MIL-125 (300 °C) with optimized Cu content, the photocatalytic degradation rate of CH3SH achieved 4.65 times higher than that of pristine NH2-MIL-125 under visible light (λ > 420 nm). At the same time, it showed great degradation efficiency under natural sunlight, 100 ppm CH3SH was completely removed within 25 min in full solar light illumination. The improved catalytic efficiency is mainly due to the synergistic effect of the integrated Schottky junction and rich-defective NH2-MIL-125, which improved the bandgap and band position, and thus facilitated the separation and transfer of the photo-generated carriers. This work provided a facile way to integrate Schottky junctions and rich-defective MOFs with high stability. Due to its excellent degradation performance under sunlight, it also offered a prospective strategy for rational design of high-efficiency catalysts applied in environmental technologies.

First report of apple rubbery wood virus 1 in apple in China.

More than 30 viral and subviral pathogens infect apple (Malus domestica, an important fruit crop in China) trees and rootstocks, posing a threat to its production. With advances in diagnostic technologies, new viruses including apple rubbery wood virus 1 (ARWV-1), apple rubbery wood virus 2 (ARWV-2), apple luteovirus 1 (ALV), and citrus virus A (CiVA) have been detected (Beatriz et al. 2018; Rott et al. 2018; Hu et al. 2021). ARWV-1 (family Phenuiviridae) is a negative-sense single-stranded RNA virus with three RNA segments (large [L], medium [M], and small [S]). It causes apple rubbery wood disease (Rott et al. 2018) and is found in apple rootstocks, causing leaf yellowing and mottle symptoms in Korea (Lim et al. 2018). To determine virus prevalence in apple trees in China, 200 apple leaf and shoot samples were collected from orchards in Hebei (n = 26), Liaoning (n = 40), Shandong (n = 100), Yunnan (n = 25), Shanxi (n = 4) and Inner Mongolia (5) in 2020. Total RNA was extracted from the shoot phloem or leaf tissues (Hu et al., 2015) and subjected to reverse transcription (RT)-PCR to detect apple chlorotic leaf spot virus (ACLSV), apple stem pitting virus (ASPV), apple stem grooving virus (ASGV), apple necrotic mosaic virus (ApNMV), apple scar skin viroid (ASSVd), ARWV-2, ARWV-1, ALVand CiVA using primers specific to respective viruses (Supplementary Table 1). The prevalence of ACLSV, ASPV, ASGV, ApNMV, ASSVd, ARWV-2, ARWV-1, ALV and CiVA was found to be 75.5%, 85.5%, 86.0%, 43.0%, 4.0%, 48.5%, 10.5%, 0% and 0%, respectively (Supplementary Table 2). Among the 21 positive samples for ARWV-1, three, five and 13 samples were from Hebei, Liaoning and Shandong, respectively. Five ARWV-1-positive samples (cultivars Xinhongjiangjun, Xiangfu-1, Xiangfu-2 and Tianhong) showed leaf mosaic symptoms. To confirm the RT-PCR assay, the projected ARWV-1 amplicons from cvs. Xiangfu-1 and Tianhong were cloned into the pMD18-T vector (Takara, Dalian, China), and three clones of each sample were sequenced. BLASTn analyses demonstrated that the sequences (accession nos. MW507810-MW507811) shared 96.9%-98.9% identity withARWV-1 sequences (MH714536, MF062127, and MF062138) in GenBank. An lncRNA library was prepared for high-throughput sequencing (HTS) with the Illumina HiSeq platform using Xiangfu-1 RNA. A total of 71,613,294 reads were obtained. De novo assembly of the reads revealed 135 viral sequence contigs of ACLSV, ASGV, ASPV, ApNMV, ARWV-1, and ARWV-2. The sequences of contig-100_88981 (302 nt) and contig-100_25701 (834 nt) (accession nos. MW507821 and MW507820) matched those of segment S from ARWV-1, whereas the sequences of contig-100_6542 (1,660 nt) and contig-100_27 (7,364 nt) (accession nos. MW507819 and MW507818) matched those of segments M and L, respectively. To confirm the HTS results, fragments of segments L (744 bp), M (747 bp), and S (554 bp) from Xiangfu-1 and Tianhong were amplified (Supplementary Table 1) and sequenced. The sequences (accession nos. MW507812-MW507817) showed 94.8%-99.9% nucleotide identity with the corresponding segments of ARWV-1. Co-infection of ARWV-1 with ApNMV and/or ARWV-2 was confirmed in 17/21 ARWV-1-positive samples. The prevalence of ARWV-1/ApNMV, ARWV-1/ARWV-2, and ARWV-1/ApNMV/ARWV-2 infections was 61.9%, 71.4%, and 52.4%, respectively. To our knowledge, this is the first report of ARWV-1 infecting apple trees in China. Further research is needed to determine whether and how ARWV-1 affects apple yield and quality.

First report of apple rubbery wood virus 2 infection of apples in China.

Apple (Malus) is one of the most widely grown fruit trees worldwide, and viral diseases can severely inhibit its growth and development. Apple rubbery wood virus 2 (ARWV-2, family Phenuiviridae) is a negative-sense single-stranded RNA virus whose genome comprises three RNA segments (large: L, medium: M, and small: S) (Rott et al. 2018). This virus is associated with apple rubbery wood disease (Rott et al. 2018) and has previously been found in pear (Pyrus spp.) in China (Wang et al. 2019). In autumn 2019, six trees (one each of cvs. Honglu, Hongzhengzhu, Jinxiuhaitang, Liquanduanfu, Huahong-1, and Huahong-2) showing mosaic disease-like symptoms in the leaves and two trees (one each of cvs. Qingming-1 and Qingming-2) showing rusty skin symptoms (i.e., a large number of irregular rust spots on the peel's surface) in the fruits were found in Xingcheng, Liaoning province, China. Shoots of the diseased plants were collected, and total RNA was extracted from the phloem of the samples as described by Hu et al. (2015). Reverse transcription (RT)-PCR was used to detect various viruses including apple chlorotic leaf spot virus (ACLSV), apple stem pitting virus (ASPV), apple stem grooving virus (ASGV), apple necrotic mosaic virus (ApNMV), and ARWV-2 as well as apple scar skin viroid (ASSVd) using their respective primers (Supplementary Table 1). ACLSV, ASPV and ASGV were detected in all samples. ApNMV was detected in the six trees with leaf mosaic symptoms and ASSVd was detected in the two trees with apple rusty skin symptoms. Moreover, five trees (cvs. Honglu, Hongzhengzhu, Jinxiuhaitang, Qingming-1, and Qingming-2) tested positive for ARWV-2 in the RT-PCR assay. The PCR products of ARWV-2 from Honglu and Qingming-2 were cloned into the pMD18-T vector (Takara, Dalian, China), and one clone of each of the samples was sequenced. BLASTn analyses showed that they shared 98.2%-99.2% nt identity with ARWV-2 sequences (MT901298-MT901299) deposited in the GenBank database. A small RNAs (sRNAs) library was prepared for high-throughput sequencing (HTS) with the Solexa-Illumina platform using phloem tissue collected from a Qingming-2 tree in which apples with rusty skin symptoms were observed. A total of 3,7746,671 reads were obtained from the library. De novo assembly of the reads yielded 1,378 viral sequence contigs. Of those, 20 contigs with lengths ranging from 82 to 387 nt were mapped to the reference genome of ARWV-2 (accession nos. MT733339-MT733344, MT901300-MT901313). In addition, contigs of ACLSV, ASPV, ASGV, ApNMV and ASSVd were detected. To further confirm the HTS results, partial length fragments of segments L (717 bp), M (645 bp), and S (657 bp) of the ARWV-2 genome were amplified from Qingming-2 using primers (Supplementary Table 1) and sequenced. The resulting sequences, which have been deposited in GenBank under the accession numbers MT364372-MT364374, showed 97.2%, 97.8%, and 98.0% nt identity, respectively, with the corresponding segments of ARWV-2 isolate R7 (accession nos. MF062144-MF062146). To understand the infection status of apple trees in China with regard to ARWV-2, 116 apple shoot samples were randomly collected from commercial orchards in Liaoning, Shanxi, and Shandong provinces and subjected to RT-PCR to detect ARWV-2, ACLSV, ASGV, ASPV, ASSVd and ApNMV. In total, 49 (42.2%) of the 116 samples tested positive for ARWV-2, suggesting that this virus is wide spread in apple trees in China (Supplementary Table 2). The mixed-infection rates of ARWV-2/ApNMV and ARWV-2/ASSVd were 18.1% (21/116) and 3.4% (4/116), respectively. Among the 46 ARWV-2-positive samples, seven had mosaic disease-like symptoms in the leaves and three had rusty skin symptoms in the fruits. To our knowledge, this is the first report of ARWV-2 infection in apples showing rusty skin symptoms, as well as the first report of ARWV-2 infection in domestic apples in China. Further research is needed to understand the distribution of ARWV-2 in apple orchards throughout China, to confirm the relationship of ARWV-2 with different symptoms and to evaluate how ARWV-2 affects the performance and quality of apple.