Prediction Of Ginkgo Distribution And Research On Environmental Response Mechanism Of Phenotypic Traits Under The Climate Change

Ginkgo(Ginkgo biloba L.)is an important economic tree species,ginkgo plantations have been widely established for leaf,fruit and wood use.Ginkgo leaves are rich in a variety of natural active substances and nutrients,including flavonoids,terpene lactones,polypentenol,and amino acids.Many countries have developed hundreds of therapeutic agents using ginkgo leaves as raw materials,which rank first among the best-selling herbal medicines.Climate change is the most concerned global issue of the scientific community in this century.It is accelerating the risk of forest extinction,leading to changes in the habitats distribution and abundance of tree species.Meanwhile,climate change would have a complex impact on the yield and quality of natural active substances in medicinal plants.Therefore,how ginkgo will respond to the challenges of climate change has become one of the most important issues and an increasing concern to plantation managers.In order to explore this scientific question,firstly,this study builted a bioclimatic model at the macro-biogeographic level to delineate the suitable habitat of ginkgo;then,we quantified the phenotypic plasticity of ginkgo leaves at the visual level,and developed climate response models of the target traits is used to delineate the distribution of ginkgo high-yield plantations;finally,the transcriptome and metabolome analysis are carried out to to identify the key genes and regulatory factors in metabolic pathways responding to environmental changes at the molecular level.These results will provide theoretical basis and practical support for formulating scientific adaptation strategies to continuously improve the economic benefits of ginkgo industry.The main conclusions are as follows:(1)In this study,we developed a bioclimatic model based on data about the occurrence of ginkgo from 277 locations,and validated model predictions using a wide-ranging field test(12test sites,located at the areas from 22.49°N to 39.32°N,and 81.11°E to 123.53°E).We found that the degree-days below zero were the most important climate variable determining ginkgo distribution.Based on the model predictions,we classified the habitat suitability for ginkgo into four categories(high suitable,suitable,secondary suitable,and low suitable),accounting for 9.29,6.09,8.46,and 76.16%of China's land area,respectively.The ANOVA results of the validation test showed significant differences in observed leaf-traits among the four habitat types(P<0.05),and importantly the rankings of the leaf traits were consistent with our classification of the habitat suitability,suggesting the effectiveness of our classification in terms of biological and economic significance.In addition,we projected that suitable(high and medium)habitats for ginkgo would shrink and shift northward under both the RCP4.5 and RCP8.5 climate change scenarios for three future periods(the 2020s,2050s,and 2080s).(2)We first examined the extent of several phenotypic traits(4 growth traits and 12metabolites traits)variation of genetically homogeneous Ginkgo clones(including gender differences)along climatic gradients.Results showed that the studied growth and metabolites traits varied significantly(P<0.05)among the 17 assessed diverse growing environments,while female trees consistently outperformed male trees for growth traits.Ginkgo has strong phenotypic plasticity.Climate variables related to sub-zero temperature were considered to be the most key factor restricting the distribution of Ginkgo(growth potential);however,they promoted the biosynthesis of some defense compounds(e.g.,flavonoids).Finally,we predicted the growth potential of the studied traits(leaf area,quercetin,and polyprenols?C₉₀)and delineated their suitable production areas under current and future climate conditions.The output of the model showed that the suitable location of ginkgo plantations is in the middle and east of China under the current climate conditions;with global warming,the area suitable for Ginkgo growth(leaf area)would increase by 7.2%by mid-century as well the high-yield,high-quality areas of Ginkgo cultivation would shift northward and upward.(3)We integrated and analyzed transcriptome and metabolome from ginkgo leaves originated from clonal homogeneous materials including their different genders(female and male)grown in three different habitats to reveal the environmental response mechanism of primary(amino acid)and secondary(flavonoids)metabolism.We found that growing in different environments,ginkgo clones underwent remarkable reprogramming of their transcriptomes and substantial changes in their metabolomes.The amino acid composition of 18 samples was relatively consistent,including 6 essential amino acids and 8 non essential amino acids.The results of transcriptome and metabolome association analysis showed that the structure genes in amino acid biosynthesis pathway were regulated by multiple transcription factors(such as MYB,NAC,and b ZIP).We suggested that the overexpression of structural genes in phenylpropanoid biosynthesis pathway and genes encoding receptor-like kinases were closely related to the amino acids'accumulation.Further,we indicated that environmental conditions directly affected the C and N flow allocation in leaves,thereby having an impact on the yield and amino acid content of ginkgo leaves.By integrating transcriptome and metabolomic data,three modules highly related to flavonoids accumulation were screened by weighted gene coexpression network analysis(WGCNA),and 13 genes encoding transcription factors were found from the core genes of the modules.These these transcription factors(such as AP2/ERF,b HLH,b ZIP,and trihelix)could play important roles in transcriptional regulation of flavonoids biosynthesis by activating or repressing the expression of multiple structural genes under different environments.