A high-quality sponge gourd(Luffa cylindrica)genome

Sponge gourd(Luffa cylindrica)is an important cultivated vegetable and medicinal plant in the family Cucurbitaceae.In this study,a draft genome sequence of the sponge gourd inbred line P93075 was analyzed.Using Illumina,PacBio,and 10×Genomics sequencing techniques as well as new assembly techniques such as FALCON and chromatin interaction mapping(Hi-C),a chromosome-scale genome of approximately 656.19 Mb,with an N50 scaffold length of 48.76 Mb,was generated.From this assembly,25,508 protein-coding gene loci were identified,and 63.81%of the whole-genome consisted of transposable elements,which are major contributors to the expansion of the sponge gourd genome.According to a phylogenetic analysis of conserved genes,the sponge gourd lineage diverged from the bitter gourd lineage approximately 41.6 million years ago.Additionally,many genes that respond to biotic and abiotic stresses were found to be lineage specific or expanded in the sponge gourd genome,as demonstrated by the presence of 462 NBS-LRR genes,a much greater number than are found in the genomes of other cucurbit species;these results are consistent with the high stress resistance of sponge gourd.Collectively,our study provides insights into genome evolution and serves as a valuable reference for the genetic improvement of sponge gourd.

Establishment of Agrobacterium tumefaciens-mediated Genetic Transformation System for Aspergillus awamori

[ Objective ] This study aimed to establish Agrobacterium tumefaciens-mediated genetic transformation system for Aspergillus awamori and investigate the feasibility of expressing heterologous proteins in A. awamori. [ Method] Appropriate A. awamori host strains were determined according to the secretory protein profile. Selectable marker was selected for genetic transformation by drug sensitivity analysis. The established A. awamori genetic transformation system was used for transformation and expression analysis of Rhizomucor miehei lipase （RML）. The feasibility of using A. awamori to express heterologous proteins was investigated by identification of transformants and property analysis. [ Result~ Based on the analysis of secretory protein profile, A. awamori strains CBS115.52 and CICC2257 were determined as the host strains for heterologous protein expression ; drug sensitivity analysis shows that hygromycin B resistance gene （ HygBr ） is an effective ge- netic seleetable marker; by using Agrobacterium tumefaciens-mediatcd transformation （ATMT） method, the plasmid pHGW-amdS containing HygBr was successfully transformed into A. awamori strain CBS115.52 to establish the genetic transformation system ofA. awamorl with HygBr as selectable marker. RML was transformed into A. awamori and its expression was validated by substrate hydrolysis test, SDS-PAGE and Western blot. [ Conclusion] This study demonstrates that the genetic transformation system of A. awamori mediated by Agrobacterium tumefaciens has potential feasibility for expression of heterologous proteins.

The role of DNA methylation in the maintenance of phenotypic variation induced by grafting chimerism in Brassica

Grafting facilitates the interaction between heterologous cells with different genomes,resulting in abundant phenotypic variation,which provides opportunities for crop improvement.However,how grafting-induced variation occurs and is transmitted to progeny remains elusive.A graft chimera,especially a periclinal chimera,which has genetically distinct cell layers throughout the plant,is an excellent model to probe the molecular mechanisms of grafting-induced variation maintenance.Here we regenerated a plant from the T-cell layer of a periclinal chimera,TCC(where the apical meristem was artificially divided into three cell layers–from outside to inside,L1,L2,and L3;T=Tuber mustard,C=red Cabbage),named rTTT0(r=regenerated).Compared with the control(rsTTT,s=self-grafted),rTTT0 had multiple phenotypic variations,especially leaf shape variation,which could be maintained in sexual progeny.Transcriptomes were analyzed and 58 phenotypic variation-associated genes were identified.Whole-genome bisulfite sequencing analyses revealed that the methylome of rTTT0 was changed,and the CG methylation level was significantly increased by 8.74%.In rTTT0,the coding gene bodies are hypermethylated in the CG context,while their promoter regions are hypomethylated in the non-CG context.DNA methylation changes in the leaf shape variation-associated coding genes,ARF10,IAA20,ROF1,and TPR2,were maintained for five generations of rTTT0.Interestingly,grafting chimerism also affected transcription of the microRNA gene(MIR),among which the DNA methylation levels of the promoters of three MIRs associated with leaf shape variation were changed in rTTT0,and the DNA methylation modification of MIR319 was maintained to the fifth generation of selfed progeny of rTTT0(rTTT5).These findings demonstrate that DNA methylation of coding and non-coding genes plays an important role in heterologous cell interaction-induced variation formation and its transgenerational inheritance.