Premise of the study: Fokienia hodginsii (Cupressaceae) is a Tertiary relict evergreen conifer of the monotypic genus Fokienia. Polymorphic microsatellite markers were developed to investigate its genetic diversity and population structure.Methods and Results: RNA transcripts of F. hodginsii were sequenced and de novo assembled into 85,818 unigenes, and 1892 simple sequence repeat (SSR) markers were detected from the unigenes. A total of 273 expressed sequence tag–SSR primer pairs were designed and tested, and 129 successfully amplified. Eleven displayed clear polymorphisms in F. hodginsii. Amplification of these polymorphic primers across three populations of F. hodginsii showed the number of alleles per locus ranged from two to seven, and the expected heterozygosity per locus varied from 0.067 to 0.847. All 11 polymorphic primers amplified in Thuja occidentalis, while 10 amplified in T. standishii, Platycladus orientalis, and Chamaecyparis obtusa.Conclusions: These microsatellite markers will be useful in exploring genetic diversity of F. hodginsii and other conifer trees.

Hybridization accompanied by polyploidization and apomixis has been demonstrated as a driving force of evolution and speciation in many plants. A good example to study the evolutionary process of hybridization associated with polyploidy and apomixis is the genus Cotoneaster (Rosaceae), which includes about 150 species, most of which are polyploid apomicts. In this study, we investigated all the Cotoneaster taxa distributed in a small region of Malipo, Yunnan, China. Based on the morphological characters, four Cotoneaster taxa were identified and sampled: C. dielsianus, C. glaucophyllus, C. franchetii, and a putative hybrid. Flow cytometry analyses showed that C. glaucophyllus was diploid, while the three other were tetraploid. Totally five low-copy nuclear genes and six chloroplast regions were sequenced to validate status of the putative hybrid. Sequence analyses showed C. dielsianus and C. glaucophyllus are distantly related, they could be well separated by totally 50 fixed nucleotide substitutions and four fixed indels at the 11 investigated genes. All the individuals of the putative hybrid harbored identical sequences: they showed chromatogram additivity for all the fixed differences between C. dielsianus and C. glaucophyllus at the five nuclear genes, and were identical with C. glaucophyllus at the six chloroplast regions. Haplotype analysis revealed C. dielsianus possessed nine haplotypes for the 11 genes, while C. glaucophyllus had ten, and there was no shared haplotypes between the two species. The putative hybrid harbored two haplotype for each nuclear gene: one was shared with C. dielsianus and the other with C. glaucophyllus. They possessed the same chloroplast haplotype with C. glaucophyllus. Our study provided convincing evidence for natural hybridization between C. dielsianus and C. glaucophyllus, and revealed that all the hybrid individuals were derivatives of one initial F1 via apomixis, and C. glaucophyllus served as maternal parent at the initial hybridization event. We proposed that anthropological disturbance provided an opportunity for hybridization between C. dielsianus and C. glaucophyllus, and a tetraploid F1 successfully bred many identical progenies via apomixis. Under this situation, species integrity could be maintained for these Cotoneaster species, yet attentions should be kept for this new-born hybrid.

Mangroves are critical marine resources for their remarkable ability to tolerate seawater. Antioxidant enzymes play an especially significant role in eliminating reactive oxygen species and conferring abiotic stress tolerance. In this study, a cytosolic copper/zinc superoxide dismutase (SaCSD1) cDNA of Sonneratia alba, a mangrove species with high salt tolerance, was successfully cloned and then expressed in Escherichia coli Rosetta-gami (designated as SaCSD1). SaCSD1 comprised a complete open reading frame (ORF) of 459 bp which encoded a protein of 152 amino acids. Its mature protein is predicted to be 15.32 kDa and the deduced isoelectric point is 5.78. SaCSD1 has high sequence similarity (85%–90%) with the superoxide dismutase (CSD) of some other plant species. SaCSD1 was expressed with 30.6% yield regarding total protein content after being introduced into the pET-15b (Sma I) vector for expression in Rosetta-gami and being induced with IPTG. After affinity chromatography on Ni-NTA, recombinant SaCSD1 was obtained with 3.2-fold purification and a specific activity of 2200 U/mg. SaCSD1 showed good activity as well as stability in the ranges of pH between 3 and 7 and temperature between 25 and 55 °C. The activity of recombinant SaCSD1 was stable in 0.25 M NaCl, Dimethyl Sulphoxide (DMSO), glycerol, and chloroform, and was reduced to a great extent in β-mercaptoethanol, sodium dodecyl sulfate (SDS), H₂O_2, and phenol. Moreover, the SaCSD1 protein was very susceptive to pepsin digestion. Real-time Quantitative Polymerase Chain Reaction (PCR) assay demonstrated that SaCSD1 was expressed in leaf, stem, flower, and fruit organs, with the highest expression in fruits. Under 0.25 M and 0.5 M salt stress, the expression of SaCSD1 was down-regulated in roots, but up-regulated in leaves.

Although it is well documented that mountains tend to exhibit high biodiversity, how geological processes affect the assemblage of montane floras is a matter of ongoing research. Here, we explore landform-specific differences among montane floras based on a dataset comprising 17,576 angiosperm species representing 140 Chinese mountain floras, which we define as the collection of all angiosperm species growing on a specific mountain. Our results show that igneous bedrock (granitic and karst-granitic landforms) is correlated with higher species richness and phylogenetic overdispersion, while the opposite is true for sedimentary bedrock (karst, Danxia, and desert landforms), which is correlated with phylogenetic clustering. Furthermore, we show that landform type was the primary determinant of the assembly of evolutionarily older species within floras, while climate was a greater determinant for younger species. Our study indicates that landform type not only affects montane species richness, but also contributes to the composition of montane floras. To explain the assembly and differentiation of mountain floras, we propose the ‘floristic geo-lithology hypothesis’, which highlights the role of bedrock and landform processes in montane floristic assembly and provides insights for future research on speciation, migration, and biodiversity in montane regions.