| The genetic background of potato cultivars is narrow,and there are sexual hybridization incompatibility between cultivars and wild species.Somatic hybridization technology can overcome the barrier of sexual hybridization and create new germplasm resources for potato breeding.Somatic hybrids of potato cultivar(AC142)and non-tuberized wild species S.etuberosum(ETB)have been obtained by somatic cell fusion technology and the biotic or abiotic resistance from S.etuberosum was intergression into them.In order to utilize these somatic hybrids in production,the traits of tuberizion of these somatic hybrids were reseached from cellular level and the molecular level.The results were as follows:1.The phenotype of tuber formation from these somatic hybrids were identified under the field conditions.Tuber performance of tetraploid hybrids was between the tuber-bearing parents and the non-tuber-bearing parents,while the performance of hexaploid hybrids appeared significant separation that some of hybrids perform good characteristics of tuberization and some can’t form tubers.In order to prove whether the tuber performance of hexaploid somatic hybrids are related to their parental genome composition,genomic in situ hybridization(GISH)verification was performed on some typical somatic hybrids of tuber-bearing and non-tuber-bearing genotypes.The results of hybridization showed that the chromosome composition of the tuber-bearing genotypes was “AAAAEE”,and the chromosome composition of the non-uber-bearing genotypes was “AAEEEE”.The GISH results confirmed the tuber performance of hexaploid somatic hybrids is associated with the parental genome composition.2.In order to verify the difference in tuber performance of hexaploid somatic hybrids on gene expression levels,transcriptome sequencing was performed.Part of tuber-bearing and non-tuber-bearing hexaploid with the two parents were induced tuberization in vitro.Because of the tuber formation of somatic hybrids were later than the cultivars parents,the time point of parents appear tuberization and all somatic hybrids appear tuberization were chosen.This samples were sequenced by transcriptome,and each time point included two parents,tuber-bearing somatic hybrids genotypes pool and non-tuber-bearing somatichybrids genotypes pool.The differentially expressed genes(DEGs)that the tuberizing parents were compared to non-tuberizing parents at the two time points,respectively,so did between the two somatic hybrids pool.The DEGs of four Comparisons were overlapped to obtain 104 co-upregulated genes and 325 co-downregulated genes.3.In order to verify the expression of genes related to tuberization in potato stolon further,the grafting experiments between potato cultivar E3 and S.etuberosum were carried out.Four grafting combinations were performed,two self-grafts that generated E3/E3 and ETB/ETB and two heterograftings in which E3 was grafted on ETB(E3/ETB)or ETB was grafted on E3(ETB/E3).The grafting results show that E3 rootstocks can tuberize and ETB rootstocks can’t tuberize whatever which species be scion.Transcriptome sequencing were carried out in the stolon of four grafting cobinations.The DEGs that the E3/E3 were compared to E3/ETB and the DEGs that the ETB/E3 were compared to ETB/ETB were overlapped,and 2,587 common up-regulated genes and 2,617 common down-regulated genes were obtained.The crossover genes screened from microtuber induction and from grafting experiments were further overlapped according to the up-or down-regulation.Since these DEGs are tuberizing sample compared to non-tuberizing sample and have common expression patterns in microtuber induction and from grafting experiments,so it is preliminarily identified that these genes are candidate genes associated with tuberization.The GO enrichment results of 60 co-upregulated genes are mainly distributed in the term of enzyme-directed rRNA 2’-O-methylation,rRNA methyltransferase activity,chaperone binding while the KEGG enrichment results of those genes are none.169 co-downregulated genes are mainly enriched in the GO term of serine endopeptidase inhibitor activity,proteasome core complex,nuclear pore,carbohydrate metabolism process and the KEGG pathway of α-linolenic acid metabolism,phenylpropanoid biosynthesis,plant hormone signal transduction.. |
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