Transcriptome Study On The Gynoecium After Heteospecific Pollination In Sagittaria

In the natural mixed population,pollinators shared by plants may lead to the phenomenon of pollen transfer between different plants.In different stage of pollination and fertilization,there are a series of mechanisms causing reproductive interference in the settlement of heterospecific pollen.The redistribution of pollen tubes is a common phenomomen in Sagittaria.Previous studies have shown that when the pollen of Sagittaria pygmaea and S.trifolia is used for conspecific and heterospecific pollination.After a while,conspecific pollen tubes entered into the ovules directly,and some pollen tube entered the ovule at 1.5 h after pollination;whereas heterospecific tubes passed through the carpel base and adjacent receptacle tissue,to ultimately fertilize other unfertilized ovules after 2.5 hours,therefore,S.trifolia's pollen may cause reproductive disturbance to the S.pygmaea.However,the molecular mechanism of the growth process of heterospecific pollen tubes in S.pygmaea's gynoecium is not clear and further exploration is needed.The study of hybridization between plants of Sagittaria can further explore the growth mechanism of pollen tube and the mechanism of pollen interference among plants of Sagittaria.In this study,the pollen of S.trifolia was granted on the side of the S.pygmaea's gynoecium,and the other side was not pollinated.The cut gynoecium of 1,1.5,2,and3 h were used as the research object,three individuals per population were selected to extract RNA and then mixed as one sample.The library was constructed for transcriptome sequencing.A total of 31.87 Mb~33.46 Mb high-quality fragments were obtained.After assembly,48306~64638 unigenes were screened out.After bioinformatics analysis,the following results and related conclusions are obtained:1.The expression characteristics of the transcriptome on S.pygmaea's gynoecium showed that the obtained Unigene is compared with the databases of Nr,Nt,Swissprot,KEGG,COG,Interpro,GO and 46637,32457,34243,37162,20792,33561,15048 are compared to the database respectively.All Unigenes with functional annotations had a total of 49,240 accounting for 62.60% of all Unigene.The transcriptome of S.pygmaea's gynoecium is classified into 25 functional categories of COG functional classification,and Unigenes classified into General function prediction only is most maximum,for 5944;followed by Transcription,for 4,377.Unigenes is classified into55 GO functional categories,the Biological process classification is mainly concentrated in the metabolic process 7733 genes,7104 cellular processes.The Cellular components classification mainly consists of 6215 cells and 6163 cell parts.The Molecular function is mainly concentrated in 7360 catalytic activities and 6108 binding.In the KEGG classification,the annotations to the Global and overview maps,Translation,Carbohydrate metabolism,Transport and catabolism,Folding,Sorting and degradation,Transcription,this six major metabolism have more unigenes,8901(22.5%),4293(10.8%),3099(7.8%),2603(6.6%),2590(6.6%),and 2207(5.6%),respectively.SSR markers showed that the proportion of trinucleotide repeats was the highest in Sagittaria,followed by dinucleotide repeats and minimal mononucleotide repeats.2.The GO annotation and KEGG pathway enrichment analysis of the differentially expressed genes in the pistils samples of the two treatments at four pollination time periods showed that the GO annotation analysis of differentially expressed genes revealed that the growth of heterospecific pollen tubes enriched biological processes such as catalytic activity,metabolic processes,cellular processes,and single-tissue processes;The KEGG pathways with the most differentially expressed genes are global and overview maps,translation,carbohydrate metabolism,environmental adaptation,biosynthesis of other secondary metabolites,transport and catabolism.3.KEGG pathway enrichment analysis of differentially expressed genes in pistils at four pollination time periods showed that 178 differentially expressed genes related to pollen tube growth had been found in planting pathogen interaction,plant hormone signal transduction,starch and sucrose metabolism,pentose and glucuronate interconversions,flavonoid biosynthesis.4.Statistical classification of differentially expressed genes belonging to different transcription factor families showed that the transcription factor genes of 254 unigenes homologous sequences belonging to 40 transcription factor families weresignificantly differentially expressed.Among them,MYB,MYB-related,AP2-EREBP,NAC,WRKY have the highest number of differentially expressed genes among the factor families.In summary,the above results preliminarily explored the molecular mechanism of the growth process of heterogenous pollen tube in S.pygmaea's gynoecium,which laid a valuable foundation for the breeding and genomics study of Sagittaria,and provided a basis for the further exploration of the pollen interference among the sibling species.