Zhongyang Tan

Turnip mosaic virus (TuMV), a species of the genus Potyvirus, occurs worldwide. Seventy-six isolates of TuMV were collected from around the world, mostly from Brassica and Raphanus crops, but also from several non-brassica species. Host tests grouped the isolates into one or other of two pathotypes; Brassica (B) and Brassica-Raphanus (BR). The nucleotide sequences of the first protein (P1) and coat protein (CP) genes of the isolates were determined. One-tenth of the isolates were found to have anomalous and variable phylogenetic relationships as a result of recombination. The 5'-terminal 300 nt of the P1 gene of many isolates was also variable and phylogenetically anomalous, whereas the 380 nt 3' terminus of the CP gene was mostly conserved. Trees calculated from the remaining informative parts of the two genes of the non-recombinant sequences by neighbour-joining, maximum-likelihood and maximum-parsimony methods were closely similar, and so these parts of the sequences were concatenated and trees calculated from the resulting 1150 nt. The isolates fell into four consistent groups; only the relationships of these groups with one another and with the outgroup differed. The "basal-B" cluster of eight B-pathotype isolates was most variable, was not monophyletic, and came from both brassicas and non-brassicas from southwest and central Eurasia. Closest to it, and forming a monophyletic subgroup of it in most trees, and similarly variable, was the "basal-BR" group of eight BR pathotype Eurasian isolates. The third and least variable group, the "Asian-BR" group, was of 22 BR-pathotype isolates, all from brassicas, mostly Raphanus, and all from east Asia mostly Japan. The fourth group of 36 isolates, the "world-B" group, was from all continents, most were isolated from brassicas and most were of the B-pathotype. The simplest of several possible interpretations of the trees is that TuMV originated, like its brassica hosts, in Europe and spread to the other parts of the world, and that the BR pathotype has recently evolved in east Asia.

A novel multilayer-structured Ti₃C₂T_x MXene/poly(vinylidene fluoride) film with a high dielectric constant and ultralow dielectric loss is presented.

Previous works have demonstrated that ligninolytic enzymes mediated effective degradation of lignin wastes. The degrading ability greatly relied on the interactions of ligninolytic enzymes with lignin. Ligninolytic enzymes mainly contain laccase (Lac), lignin peroxidase (LiP) and manganese peroxidase (MnP). In the present study, the binding modes of lignin to Lac, LiP and MnP were systematically determined, respectively. Robustness of these modes was further verified by molecular dynamics (MD) simulations. Residues GLU460, PRO346 and SER113 in Lac, residues ARG43, ALA180 and ASP183 in LiP and residues ARG42, HIS173 and ARG177 in MnP were most crucial in binding of lignin, respectively. Interactional analyses showed hydrophobic contacts were most abundant, playing an important role in the determination of substrate specificity. This information is an important contribution to the details of enzyme-catalyzed reactions in the process of lignin biodegradation, which can be used as references for designing enzyme mutants with a better lignin-degrading activity.

A recombination map of the genome of Turnip mosaic virus (TuMV) was assembled using data from 19 complete genomic sequences, previously reported, and a composite sample of three regions of the genome, one-third in total, of a representative Asia-wide collection of 70 isolates. Thus, a total of 89 isolates of worldwide origin was analysed for recombinants. Eighteen recombination sites were found spaced throughout the 5' two-thirds of the genome, but there were only two in the 3' one-third; thus, 24 and 35 % of the P1 and NIa-VPg gene sequences examined were recombinants, whereas only 1 % of the corresponding NIa-Pro and CP gene sequences were recombinants. Recombinants with parents from the same or from different lineages were found, and some recombination sites characterized particular lineages. Most of the strain BR recombinants belonged to the Asian-BR group, as defined previously, and it was concluded that this lineage resulted from a recent migration, whereas many of the strain B recombinants from Asia fell into the world-B group. Again, a large proportion of isolates in this group were recombinants. Some recombination sites were found only in particular lineages, and hence seemed more likely to be the surviving progeny from single recombinational events, rather than the progeny of multiple events occurring at recombination hotspots. It seems that the presence of recombination sites, as well as sequence similarities, may be used to trace the migration and evolution of TuMV.