Telomere-to-telomere pear (Pyrus pyrifolia) reference genome reveals segmental and whole genome duplication driving genome evolution

Previously released pear genomes contain a plethora of gaps and unanchored genetic regions.Here,we report a telomere-to-telomere(T2T)gap-free genome for the red-skinned pear,‘Yunhong No.1’(YH1;Pyrus pyrifolia),which is mainly cultivated in Yunnan Province(southwest China),the pear’s primary region of origin.The YH1 genome is 501.20 Mb long with a contig N50 length of 29.26 Mb.All 17 chromosomes were assembled to the T2T level with 34 characterized telomeres.The 17 centromeres were predicted and mainly consist of centromeric-specific monomers(CEN198)and long terminal repeat(LTR)Gypsy elements(≥74.73%).By filling all unclosed gaps,the integrity of YH1 is markedly improved over previous P.pyrifolia genomes(‘Cuiguan’and‘Nijisseiki’).A total of 1531 segmental duplication(SD)driven duplicated genes were identified and enriched in stress response pathways.Intrachromosomal SDs drove the expansion of disease resistance genes,suggesting the potential of SDs in adaptive pear evolution.A large proportion of duplicated gene pairs exhibit dosage effects or sub-/neo-functionalization,whichmay affect agronomic traits like stone cell content,sugar content,and fruit skin russet.Furthermore,as core regulators of anthocyanin biosynthesis,we found that MYB10 and MYB114 underwent various gene duplication events.Multiple copies of MYB10 and MYB114 displayed obvious dosage effects,indicating role differentiation in the formation of red-skinned pear fruit.In summary,the T2T gap-free pear genome provides invaluable resources for genome evolution and functional genomics.

The involvement of PybZIPa in light-induced anthocyanin accumulation via the activation of PyUFGT through binding to tandem G-boxes in its promoter

To gain insight into how anthocyanin biosynthesis is controlled by light in fruit,transcriptome and metabolome analyses were performed in the Chinese sand pear cultivar“Mantianhong”(Pyrus pyrifolia)after bagging and bag removal.We investigated transcriptional and metabolic changes and gene-metabolite correlation networks.Correlation tests of anthocyanin content and transcriptional changes revealed that 1,530 transcripts were strongly correlated with 15 anthocyanin derivatives(R2>0.9,P-value<0.05),with the top 130 transcripts categorized as being associated with flavonoid metabolism,transcriptional regulation,and light signaling.The connection network revealed a new photosensitive transcription factor,PybZIPa,that might play an important role during light-induced anthocyanin accumulation.The overexpression of PybZIPa promoted anthocyanin accumulation in pear and strawberry fruit as well as tobacco leaves.Dual luciferase and Y1H assays further verified that PybZIPa directly activated the expression of PyUFGT by binding to tandem G-box motifs in the promoter,which was key to differential anthocyanin accumulation in debagged pear skin,and the number of G-box motifs affected the transcriptional activation of PyUFGT by PybZIPa.The results indicate that the light-induced anthocyanin biosynthesis regulatory mechanism in pear differs from that described in previous reports suggesting that a bZIP family member co-regulates anthocyanin biosynthesis with other transcription factors in apple and Arabidopsis.It was found that,in response to light,PybZIPa promoted anthocyanin biosynthesis by regulating important transcription factors(PyMYB114,PyMYB10,and PyBBX22)as well as structural genes(PyUFGT)via binding to G-boxes within promoters.This activation was amplified by the self-binding of PybZIPa to activate its own promoter.Overall,we demonstrate the utility of a multiomics integrative approach for discovering new functional genes and pathways underlying light-induced anthocyanin biosynthesis.

Evolution laws of microstructures and mechanical properties during heat treatments for near-αhigh-temperature titanium alloys

Evolution laws of microstructures,mechanical properties,and fractographs after different solution temperatures were investigated through various analysis methods.With the increasing solution temperatures,contents of the primaryαphase decreased,and contents of transformedβstructures increased.Lamellarαgrains dominated the characteristics of transformedβstructures,and widths of secondaryαlamellas increased monotonously.For as-forged alloy,large silicides with equiaxed and rod-like morphologies,and nano-scale silicides were found.Silicides with large sizes might be(Ti,Zr,Nb)_(5)Si_(3) and(Ti,Zr,Nb)_(6)Si_(3).Rod-like silicides with small sizes precipitated in retainedβphase,exhibiting near 45°angles withα/βboundaries.Retainedβphases in as-heat treated alloys were incontinuous.980STA exhibited an excellent combination of room temperature(RT)and 650°C mechanical properties.Characteristics of fracture surfaces largely depended on the evolutions of microstructures.Meanwhile,silicides promoted the formation of mico-voids.

The PyPIF5-PymiR156a-PySPL9-PyMYB114/ MYB10 module regulates light-induced anthocyanin biosynthesis in red pear

Some cultivars of pear(Pyrus L.)show attractive red fruit skin due to anthocyanin accumulation.This pigmentation can be affected by environmental conditions,especially light.To explore the light-induced regulation network for anthocyanin biosynthesis and fruit coloration in pear,small RNA libraries and mRNA libraries from fruit skins of‘Yunhongyihao’pear were constructed to compare the difference between bagging and debagging treatments.Analysis of RNA-seq of fruit skins with limited light(bagged)and exposed to light(debagged),showed that PyPIF5 was down-regulated after bag removal.PymiR156a was also differentially expressed between bagged and debagged fruit skins.We found that PyPIF5 negatively regulated PymiR156a expression in bagged fruits by directly binding to the G-box motif in its promoter.In addition,PymiR156a overexpression promoted anthocyanin accumulation in both pear skin and apple calli.We confirmed that PymiR156a mediated the cleavage of PySPL9,and that the target PySPL9 protein could form heterodimers with two key anthocyanin regulators(PyMYB114/PyMYB10).We proposed a new module of PyPIF5-PymiR156a-PySPL9-PyMYB114/MYB10.When the bagged fruits were re-exposed to light,PyPIF5 was down-regulated and its inhibitory effect on PymiR156a was weakened,which leads to degradation of the target PySPL,thus eliminating the blocking effect of PySPL on the formation of the regulatory MYB complexes.Ultimately,this promotes anthocyanin biosynthesis in pear skin.

Influences of boron contents on microstructures and mechanical properties of as-casted nearαtitanium alloy

Ti-6.5 Al-2.5 Sn-9 Zr-0.5 Mo-0.25 Si-1 Nb-1 W-0.1 Er-x B(x=0,0.1,0.2,0.4,0.6 and 0.8 wt%)with different boron contents are fabricated for investigation.Influences of boron element and its amounts on phase constitutions,microstructures,textures and compression mechanical properties are carefully studied.With the increasing boron additions,contents of TiB phase increase,and the maximum intensities of textures decrease.Microstructures are significantly and continuously refined after adding boron element and with the increasing boron additions,and turning point of refinement rates for different microstructural parameters is found at 0.2 wt%boron content.Strengths increase monotonously,while elongations increase firstly and decrease afterwards.The maximum value of elongation is acquired at boron content of 0.2 wt%.On the premise of ensuring plasticity,0.2 wt%boron content is the most appropriate amount for microstructural refinement and mechanical properties enhancement for current nearαtitanium alloys.Meanwhile,aspect ratios of TiB whiskers increase with the increasing boron contents.Lots of near equiaxedαgrains orαgrains with irregular morphologies are discovered around TiB phase.Distorted and twistedαgrain boundaries are also obviously detected in boron containing alloys.Moreover,premature fracture of alloys containing TiB whiskers is largely influenced by the fracture of these brittle reinforcements.