Transcriptome Response Of The Mangrove Plant Kandelia Obovata At Different Latitudes

Mangrove plants occupy a unique niche,growing in tropical and subtropical estuaries and intertidal areas.Due to the high temperature,high salinity,tidal inundation,and strong UV radiation in its growing environment,mangroves have developed a unique set of adaptive mechanisms,including vivipary,abundant secondary metabolites and strong and robust root systems.Because of the special habitat and unique adaptation mechanisms,mangrove plays important functions in the coastal wetland ecosystem.The mangroves serve the functions of providing shelter and habitat for intertidal aquatic organisms,protection from wind and waves and embankments.Mangroves are increasingly valued and protected because of the important ecological roles of mangrove plants.In areas north of the natural distribution range of mangroves,people try to establish mangrove forest by afforestation,but the results are often not all satisfactory.It is unclear which aspects of mangrove plants are affected by transplanting,and there is a lack of theoretical basis at the molecular level for seed source selection in artificial afforestation.In order to elucidate the impact of transplanting at different latitudes on mangrove plants,we selected the most cold-tolerant mangrove species Kandelia obovata as the research object.We sequenced the transcriptome and did comparative transcriptome analysis of the transplanting plants at high latitudes and low latitudes to understand the biological functions affected by transplanting through differential expression genes.The main results are as follows:(1)The results showed that 2671 genes were differentially expressed in high latitude and 667 genes were differentially expressed in low latitude.The results of pathway enrichment showed that these genes were involved in phenylpropanoid biosynthesis,flavonoid biosynthesis,plant hormone signal transduction,plant circadian rhythm and plant pathogen interaction.(2)Further analyses of the pathways involved in the differential genes after transplantation showed that the genes related to the synthesis of secondary metabolites were down regulated.High latitude transplant individuals are more seriously affected.The genes of plant-pathogen pathway related to plant immunity are down-regulated,while the genes related to abscisic acid(ABA)metabolism and signal transduction are up-regulated.The results showed that the transplanted K.obovata might be more sensitive to pathogens and susceptible to pathogens.The transplanted plants might be more sensitive to abscisic acid,which may lead to the inhibition of plant growth.(3)Transcription factor analysis of differential expressed genes produced by transplants at different latitudes.266 transcription factors were differentially expressed in the high-latitude transplantation group and 74 transcription factors were differentially expressed in the low-latitude transplantation group.These transcription factors are involved in the regulation of plant secondary metabolism,circadian rhythms,immune defenses,and flowering processes.Differential expression of these transcription factors may be related to the sunshine duration caused by latitude differences and may have contributed to differences in flowering times.(4)In a reciprocal transplantation experiment between two populations of Kandelia obovata,we explored whether K.obovata genes were differentially expressed in native and non-native areas,and screened 943 genes that were affected by genotypeby-environment interactions(G×E).783 of these genes showed higher expression levels in the native than in the non-native and 160 showed lower expression levels in the native than in the non-native.These genes are involved in carbohydrate metabolism,secondary metabolism,and plant hormone signal transduction in the K.obovata.We hypothesized that the basal and secondary metabolism levels in the native site were higher than those in the non-native site,allowing for better adaptation to the environment and resistance to biotic and abiotic stresses when grown in the native site.In this study,we analyzed the differential genes produced by transplantation of K.obovata at different latitudes to understand the mechanisms of K.obovata response to temperature differences at different latitudes and the effect of the transplantation process on the transcriptome level of K.obovata.This study provides data at the molecular level for mangrove plant afforestation studies to higher latitudes,as well as a reference and indication of how to improve afforestation survival rates.At the same time,this study provides transcriptome-level evidence for local adaptation studies of the K.obovata,providing new information for future ecological studies of mangrove plants.