The metagenomics of soil bacteria and fungi and the release of mechanical dormancy in hard seeds.

Persistence in the soil is a function of seed physiology, particularly non-germination and inherent lifespan. However, for seeds with mechanical dormancy, non-germination is also a function of the composition and activity of the soil microbiota. We attempted to screen out microorganisms in the soil that can specifically and rapidly decompose the hard fruit pericarps of Tilia miqueliana Maxim., a unique native tree species in China. Using the classical replica plating method, more than 100 different culturable microorganisms that could rapidly erode the pericarp were collected from the surface of pericarps under different culture conditions. At the same time, we successfully extended the concept of metagenomics and applied it to the identification of mixed artificial cultures. The decomposition process of the pericarps in soil was also simulated artificially. The physical and chemical data suggested a potential mechanism of microbial scarification and cracking in pericarp, whilst the embryos inside the eroded fruits retained good viability. Our discoveries could pave the way for the removal of physical and mechanical obstacles that prevent hard coat seeds from germinating. We anticipate that the use of this technology will improve the germination of other hard coat seeds. More research is needed to investigate the impacts on other seeds. The findings of this research can inform the design of experiments on the seed ecology of persistence.

Ecological regulation of water level should be combined with seed supplementation for lakeshore Carex community restoration in Yangtze-disconnected lakes.

Carex communities in most Yangtze-disconnected lakes have been degraded severely due to alterations in water level fluctuations. To explore the feasibility of restoring the lakeshore Carex communities through ecological regulation of water level, the present study selected the Yangtze-connected Qili Lake (the lakeshore was dominated by Carex) and the Yangtze-disconnected Wuchang Lake (the lakeshore was dominated by Zizania latifolia) as model systems, and analyzed the lakeshore seed bank characteristics and seed-related quantitative, morphological, and germination traits of three representative Carex species. According to the results, although Carex seed density in the Qili Lake seed bank was obviously higher than that in Wuchang Lake, their contribution to the total seed density in both lakes was extremely low, with no significant difference between the two lakes. The results indicate that restoration of the degraded Carex communities using existing seed bank in Yangtze-disconnected lakes exclusively through water level regulation is not feasible. In addition, the seed densities of aboveground parts of Carex cinerascens, Carex dimorpholepis, and Carex argyi in Qili Lake were 6.9 × 104, 45.1 × 104, and 3.6 × 104 seeds/m2, respectively, which can provide high numbers of seeds continuously for lakeshore Carex restoration. The results of seed germination experiments showed that light, burial depth, and their interaction had significant effects on seed germination of the three species, whereas water condition had a significant effect only on C. dimorpholepis seed germination. The average germination rates of the three Carex species were 16.63 %, 19.06 %, and 7.78 %, respectively. However, considering the high seed densities in the aboveground parts of the three species, there are considerable numbers of seeds that can be used for Carex restoration. Therefore, the restoration of Carex communities in lakeshore zones of Yangtze-disconnected lakes is still possible if water level regulation can be combined with natural or artificial seed supplementation.

Methodological and physiological study of seed dormancy release in Tilia henryana.

Tilia henryana is a rare tree of the Tilia family, found exclusively in China. Its seeds have severe dormancy features that limit its normal conditions of reproduction and renewal. Its seeds have severe dormant characteristics that limit its normal conditions of reproduction and renewal. The Dormancy in T. henryana seeds is a comprehensive dormancy (PY + PD) caused by mechanical and permeability barriers of seed coat and the presence of germination inhibitor in endosperm. L9 (34) orthogonal test was used to determine the best procedure for releasing the dormancy of T. henryana seeds, that is, first treating the seeds with H2SO4 for 15 min, followed by the application of 1 g L-1 GA3, stratification at 5 °C for 45 days, and finally germination at 20 °C, which can achieve a 98% seed germination rate. Large amounts of fat are consumed throughout the dormancy release process. As quantities of protein and starch marginally increase, soluble sugars are continuously decreased. Acid phosphatase and amylase activities increased rapidly, and the combined enzyme activities of G-6-PDH and 6-PGDH related to the PPP were also significantly increased. The levels of GA and ZR continued to increase, while the levels of ABA and IAA gradually decreased, among which GA and ABA changed most rapidly. The total amino acids content continued to decrease. Asp, Cys, Leu, Phe, His, Lys and Arg decreased with dormancy release, while Ser, Glu, Ala, Ile, Pro and Gaba showed an upward trend. The physical dormancy of T. henryana seeds is broken with H2SO4 in order to make the seed coat more permeable, which is a prerequisite for germination. As a result, the seeds can absorb water and engage in physiological metabolic activities, particularly the hydrolysis and metabolism of fat, which supply a significant amount of energy for dormancy release. In addition, rapid variations in the levels of different endogenous hormones and free amino acids, induced by cold stratification and GA3 application, are another important factor promoting the quick physiological activation of seeds and breaking the endosperm barrier.

Morphological, phenological, and transcriptional analyses provide insight into the diverse flowering traits of a mutant of the relic woody plant Liriodendron chinense.

Flowering is crucial to plant reproduction and controlled by multiple factors. However, the mechanisms underlying the regulation of flowering in perennial plants are still largely unknown. Here, we first report a super long blooming 1 (slb1) mutant of the relict tree Liriodendron chinense possessing a prolonged blooming period of more than 5 months, in contrast to the 1 month blooming period in the wild type (WT). Phenotypic characterization showed that earlier maturation of lateral shoots was caused by accelerated axillary bud fate, leading to the phenotype of continuous flowering in slb1 mutants. The transcriptional activity of genes related to hormone signaling (auxin, cytokinin, and strigolactone), nutrient availability, and oxidative stress relief further indicated active outgrowth of lateral buds in slb1 mutants. Interestingly, we discovered a unique FT splicing variant with intron retention specific to slb1 mutants, representing a potential causal mutation in the slb1 mutants. Surprisingly, most slb1 inbred offspring flowered precociously with shorter juvenility (~4 months) than that (usually 8-10 years) required in WT plants, indicating heritable variation underlying continuous flowering in slb1 mutants. This study reports an example of a perennial tree mutant that flowers continuously, providing a rare resource for both breeding and genetic research.

Morphological, physiological and biochemical changes in Magnolia zenii Cheng seed during development.

An understanding of the seed dynamics of endangered plant species, such as Magnolia zenii Cheng, is important for successful conservation. This study examined the morphological, physiological and biochemical changes that occur in M. zenii Cheng during seed development to determine the appropriate harvest stage. The appearance of the seeds was influenced by the physiological and biochemical changes occurring during the developmental period, during which the colour of the fruits changed from green to red, while that of the seed changed from light brown to dark brown. There was a significant decrease in the seed moisture content from 90 to 120 days after flowering (DAF); however, there was no significant change from 135 to 165 DAF. The seeds from 135 DAF onwards showed developed cotyledonary embryos. The seed viability exceeded 95% from 135 DAF onwards; however, the germination percentage was 0, hypothesising that the seeds of M. zenii Cheng might exhibit physiological dormancy under certain conditions of this experiment. There was a significant increase in the fat, soluble sugar and soluble starch content of the seeds while approaching maturity. There were significant changes in malate dehydrogenase (MDH), glucose-6-phosphate dehydrogenase (G-6-PDH), 6-phosphogluconate dehydrogenase (6-PGDH) and ß-amylase activities in the seeds during the developmental period. At 135-165 DAF, the MDH activity remained stable, whereas that of 6-PGDH reached its maximum, indicating that the seeds underwent vigorous metabolism. The findings of this study provide a theoretical basis for researching seed dormancy and seed harvest time.

Characterization of new microsatellite markers based on the transcriptome sequencing of Clematis finetiana.

BACKGROUND: Clematis is the biggest genus in the family Ranunculaceae with about 300 species. Clematis is also a globally important commercial group of flowers, especially in the United States and European countries. Their petals with different colors and shapes make the genus the "Queen of the Vines". However, the genomic information and phylogeny of Clematis based on existing molecular studies are limited. In this paper, new microsatellites (SSR) markers were identified from the transcriptome data of C. finetiana obtained using the Illumina paired-end sequencing technology. RESULTS: Sequences on a total of 71,900 high-quality unigenes with the mean length of 865 bp were produced in this study. There were 6192unigenes annotated and classified into 49 functional sub-groups in three main ontology categories in GO (Gen Ontology) database,14,022 unigenes mapped to COGs (Clusters of Orthologous Groups) database and classified into 25 functional categories, and 21,494 unigenes obtained and divided into 128 pathways of KEGG (Kyoto Encyclopedia of Genes) Database. A total of 7532 SSRs were discovered from 6337 unigenes. We randomly tested 210 primer pairs, of which 52 primer pairs were able to generate specific products, and 19 possessed polymorphism in the 13 wild populations of six species from Clematis, which were used as a test material. CONCLUSIONS: The dataset of C. finetiana transcriptome and the identified new SSR markers will promote genetic research and breeding effort in Clematis.

Isolation, Expression, and Promoter Analysis of GbWRKY2: A Novel Transcription Factor Gene from Ginkgo biloba.

WRKY transcription factor is involved in multiple life activities including plant growth and development as well as biotic and abiotic responses. We identified 28 WRKY genes from transcriptome data of Ginkgo biloba according to conserved WRKY domains and zinc finger structure and selected three WRKY genes, which are GbWRKY2, GbWRKY16, and GbWRKY21, for expression pattern analysis. GbWRKY2 was preferentially expressed in flowers and strongly induced by methyl jasmonate. Here, we cloned the full-length cDNA and genomic DNA of GbWRKY2. The full-length cDNA of GbWRKY2 was 1,713 bp containing a 1,014 bp open reading frame encoding a polypeptide of 337 amino acids. The GbWRKY2 genomic DNA had one intron and two exons. The deduced GbWRKY2 contained one WRKY domain and one zinc finger motif. GbWRKY2 was classified into Group II WRKYs. Southern blot analysis revealed that GbWRKY2 was a single copy gene in G. biloba. Many cis-acting elements related to hormone and stress responses were identified in the 1,363 bp-length 5'-flanking sequence of GbWRKY2, including W-box, ABRE-motif, MYBCOREs, and PYRIMIDINE-boxes, revealing the molecular mechanism of upregulated expression of GbWRKY2 by hormone and stress treatments. Further functional characterizations in transiently transformed tobacco leaves allowed us to identify the region that can be considered as the minimal promoter.