Predicting Quercus gilva distribution dynamics and its response to climate change induced by GHGs emission through MaxEnt modeling.

Quercus gilva, an evergreen tree species in Quercus section Cyclobalanopsis, is an ecologically and economically valuable species in subtropical regions of East Asia. Predicting the impact of climate change on potential distribution of Q. gilva can provide a scientific basis for the conservation and utilization of its genetic resources, as well as for afforestation. In this study, 74 distribution records of Q. gilva and nine climate variables were obtained after data collection and processing. Current climate data downloaded from WorldClim and future climate data predicted by four future climate scenarios (2040s SSP1-2.6, 2040s SSP5-8.5, 2060s SSP1-2.6, and 2060s SSP5-8.5) mainly based on greenhouse gases emissions of distribution sites were used in MaxEnt model with optimized parameters to predict distribution dynamics of Q. gilva and its response to climate change. The results showed that the predicted current distribution was consistent with natural distribution of Q. gilva, which was mainly located in Hunan, Jiangxi, Zhejiang, Fujian, Guizhou, and Taiwan provinces of China, as well as Japan and Jeju Island of South Korea. Under current climate conditions, precipitation factors played a more significant role than temperature factors on distribution of Q. gilva, and precipitation of driest quarter (BIO17) is the most important restriction factor for its current distribution (contribution rate of 57.35%). Under future climate conditions, mean temperature of driest quarter (BIO9) was the essential climate factor affecting future change in potential distribution of Q. gilva. As the degree of climatic anomaly increased in the future, the total area of predicted distribution of Q. gilva showed a shrinking trend (decreased by 12.24%-45.21%) and Q. gilva would migrate to high altitudes and latitudes. The research results illustrated potential distribution range and suitable climate conditions of Q. gilva, which can provide essential theoretical references for the conservation, development, and utilization of Q. gilva and other related species.

High-quality haplotype-resolved genome assembly for ring-cup oak (Quercus glauca) provides insight into oaks demographic dynamics.

Quercus section Cyclobalanopsis represents a dominant woody lineage in East Asian evergreen broadleaved forests. Regardless of its ecological and economic importance, little is known about the genomes of species in this unique oak lineage. Quercus glauca is one of the most widespread tree species in the section Cyclobalanopsis. In this study, a high-quality haplotype-resolved reference genome was assembled for Q. glauca from PacBio HiFi and Hi-C reads. The genome size, contig N50, and scaffold N50 measured 902.88, 7.60, and 69.28 Mb, respectively, for haplotype1, and 913.28, 7.20, and 71.53 Mb, respectively, for haplotype2. A total of 37,457 and 38,311 protein-coding genes were predicted in haplotype1 and haplotype2, respectively. Homologous chromosomes in the Q. glauca genome had excellent gene pair collinearity. The number of R-genes in Q. glauca was similar to most East Asian oaks but less than oak species from Europe and America. Abundant structural variation in the Q. glauca genome could contribute to environmental stress tolerance in Q. glauca. Sections Cyclobalanopsis and Cerris diverged in the Oligocene, in agreement with fossil records for section Cyclobalanopsis, which document its presence in East Asia since the early Miocene. The demographic dynamics of closely related oak species were largely similar. The high-quality reference genome provided here for the most widespread species in section Cyclobalanopsis will serve as an essential genomic resource for evolutionary studies of key oak lineages while also supporting studies of interspecific introgression, local adaptation, and speciation in oaks.

[Effect of Cr(VI) stress on growth of three herbaceous plants and their Cr uptake].

In order to elucidate the toxic mechanisms of Trifolium repens, Festuca arundinacea and Medicago sativa under chromium [Cr (VI)] stress, provide a theoretic foundation for phytoremediation of Cr-contaminated soil, pot experiment was conducted to investigate the effects of Cr(VI) on plant growth, physiological characteristics, Cr accumulation and distribution in three herbaceous plants. Soil sample was treated by adding K2Cr2O7 with the Cr(VI) concentration of 0, 100, 200, 300 and 400 mg x kg(-1), respectively. The results indicated that the average tolerance indices of T. repens, F. arundinacea and M. sativa were 62.5, 48.3 and 36.33, respectively. Compared with control group, contents of chlorophyll, the activity of superoxide dismutase(SOD) and peroxidase (POD) were 57.14%, 51.51%, 35.76% and 63.27%, 52.96%, 41.36% in T. repens, and F. arundinacea, respectively, but M. sativa died in 400 mg x kg(-1) Cr(VI) treatment. The plant height, root length, dry mass of roots and shoots decreased under Cr(VI) stress in three herbaceous plants, and M. sativa > F. arundinacea > T. repens, however, the content of malonyldialdehyde (MDA) increased compared to the control, and the variation range of M. sativa was the highest, while T. repens was the smallest among them. The tolerance of Cr( VI) was T. repens > F. arundinacea > M. sativa. Cr mainly distributed in cell wall and then in the cytoplasm, and less distributed in the mitochondrion and chloroplast in leaves of three herbaceous plants, whereas the content of chlorophyll, MDA, the activity of SOD and POD correlated well with Cr accumulation in the mitochondrion and chloroplast. Cr concentration in the subcellular of leaves increased with the adding Cr(VI) concentration,and M. sativa > F. arundinacea > T. repens. In comparison with T. repens, F. arundinacea, Cr concentration in the leaves of M. sativa was the maximal, i.e. 51.44 mg x kg(-1), and the proportions in the mitochondrion (18.04%) and chloroplast (19.09%) were also higher in 300 mg x kg(-1) Cr(VI). The average accumulation factors of shoots/roots were 1.22/1.54, 1.16/1.44 and 1.26/1.62, while the average translocation factors were 0.78, 0.78 and 0.74 in T. repens, F. arundinacea and M. sativa, respectively. The results suggest that T. repens and F. arundinacea are promising for the phytoremediation of Cr-contaminated soil.