Karyotype,Phenotype And Gene Expression Analysis Of Pentaploid Wheats And Their Selfed Progenies

Wheat is a widely cultivated crops and an important species on the study of polyploidy and aneuploidy.As natural species,tetraploid wheat and hexaploid wheat are extensively studied while their hybrids,i.e.,pentaploid wheat have drawn little attention.However,as a link of tetraploid wheat and hexaploid wheat for the mutual exchange of genetic information,pentaploid wheat plays an important role in the evolutionary history of hexaploid wheat.Pentaploid wheat and its derived progenies are a suitable system to investigate the genetic basis of the capacity to buffer and sustain imbalanced D subgenome chromosomes by the BBAA component of hexaploid wheat.It enables further understanding of the evolution of wheat and helps judicious designing of inter-ploidy crosses to increase the breeding efficiency.In this study,we characterized each individual of progenies of pentaploid wheat and assessed how aneuploidy affected the phenotypes.We then analyzed genome-,subgenome-and chromosome-wide gene expression of pentaploid wheat and D chromosome monosomic addition lines.These efforts may provide new insights to the understanding of gene expression and the subgenome interplay of hexaploid wheat.In this study,we constructed four pentaploid wheats with several distinct yet complementary features.Pentaploid wheat XE was generated from the cross of a resynthesized hexaploid wheat XX329(BBAADD)with an extracted tetraploid wheat(ETW,BBAA).Pentaploid wheat TE was produced by crossing hexaploid common wheat(Triticum aestivum,cv.TAA10,the donor of ETW)with ETW.XE and TE therefore share the same homozygous BBAA genome of ETW but different sources of the D subgenome.Pentaploid wheat ST was generated from the cross of newly synthesized wheat SHW(by hybridizing and doubling of F1 hybrid between TTR13 and TQ18)with TTR13.Thus,ST contains a homozygous BBAA genome of TTR13.Pentaploid wheat TT was generated from the cross of TAA10 with TTR13 and it contains a heterozygous BBAA genome.The four pentaploid wheats were self pollinated to produce F1 populations.Karyotyping by FISH,GISH and phenotyping of nine traits were conducted for the F1 progenies of the four pentaploid wheats.And whole genome gene expression was investigated in the pentaploid wheat and available D chromosome monosomic addition lines by transcriptome sequencing.Major findings of this study are summarized as the following.1.Numerical chromosome variations of A and B chromosomes and structural chromosome variations were common in F1 progenies of the four pentaploid wheats.The XE,TE and TT derived cohorts were comprised of more diversity,extreme and complex aneuploidy and was significantly different from the progeny swarms of ST.By considering the genetic background,we concluded that the BBAA component of hexaploid common wheat possesses a significantly stronger capacity to buffer and sustain imbalanced D chromosomes and appears to harbor more structural chromosome variations.We also document that this capacity in the hexaploid BBAA subgenomes behaves as a genetically controlled dominant trait.2.The extreme aneuploid was more detrimental than moderate aneuploid on phenotypes.3.In pentaploid wheat of XE and TE,the halved dosage of D subgenome induced genes being dysregulated and showing up-regulated in the BBAA subgenome comparing to their hexaploid parents of XX329 and TAA10.But the A and B subgenome were not making a difference in transcriptional response to the changed ploidy of D subgenome.The genes residing on D chromosomes of pentaploid wheat elicited both dosage effects and dosage compensation.4.All the genes residing on the BBAA subgenome of 1D,2D,3D,5D,7D monosomic addition lines showed transcriptional responses to the monosomic D chromosome,but the extent was distinctly for the differential BBAA genetic background and specific D chromosome.And the BBAA subgenome was more transcriptional response to 7D than to 5D.There was scarcely no significant difference in the distribution of differential expressed genes in A and B subgenomes.It reflected no subgenome bias of transcriptional response by the additional D chromosome.A and B homeologous chromosomes in the tetraploid wheat are rarely coregulated in response to corresponding D homeologous chromosome and the homeologous genes still greatly maintain the expression pattern of tetraploid wheat.