The chromosome-level genome of double-petal phenotype jasmine provides insights into the biosynthesis of floral scent

Jasmine(Jasminum sambac Aiton)is a well-known cultivated plant species for its fragrant flowers used in the perfume industry and cosmetics.However,the genetic basis of its floral scent is largely unknown.In this study,using PacBio,Illumina,10×Genomics and highthroughput chromosome conformation capture(Hi-C)sequencing technologies,a high-quality chromosome-level reference genome for J.sambac was obtained,exploiting a double-petal phenotype cultivar‘Shuangbanmoli’(JSSB).The results showed that the final assembled genome of JSSB is 580.33 Mb in size(contig N50=1.05 Mb;scaffold N50=45.07 Mb)with a total of 39618 predicted protein-coding genes.Our analyses revealed that the JSSB genome has undergone an ancient whole-genome duplication(WGD)event at 91.68 million years ago(Mya).It was estimated that J.sambac diverged from the lineage leading to Olea europaea and Osmanthus fragrans about 28.8 Mya.On the basis of a combination of genomic,transcriptomic and metabolomic analyses,a range of floral scent volatiles and genes were identified involved in the benzenoid/phenylpropanoid and terpenoid biosynthesis pathways.The results provide new insights into the molecular mechanism of its fragrance biosynthesis in jasmine.

Installing the neurospora carotenoid pathway in plants enables cytosolic formation of provitamin A and its sequestration in lipid droplets

Vitamin A deficiency remains a severe global health issue,which creates a need to biofortify crops with provitamin A carotenoids(PACs).Expanding plant cell capacity for synthesis and storing of PACs outside the plastids is a promising biofortification strategy that has been little explored.Here,we engineered PAC formation and sequestration in the cytosol of Nicotiana benthamiana leaves,Arabidopsis seeds,and citrus callus cells,using a fungal(Neurospora crassa)carotenoid pathway that consists of only three enzymes converting C5 isopentenyl building blocks formed from mevalonic acid into PACs,including β-carotene.This strategy led to the accumulation of significant amounts of phytoene and γ-and β-carotene,in addition to fungal,health-promoting carotenes with 13 conjugated double bonds,such as the PAC torulene,in the cytosol.Increasing the isopentenyl diphosphate pool by adding a truncated Arabidopsis hydroxymethylglutaryl-coenzyme A reductase substantially increased cytosolic carotene production.Engineered carotenes accumulate in cytosolic lipid droplets(CLDs),which represent a novel sequestering sink for storing these pigments in plant cytosol.Importantly,β-carotene accumulated in the cytosol of citrus callus cells was more light stable compared to compared with plastidialβ-carotene.Moreover,engineering cytosolic carotene formation increased the number of large-sized CLDs and the levels of β-apocarotenoids,including retinal,the aldehyde corresponding to vitamin A.Collectively,our study opens up the possibility of exploiting the high-flux mevalonic acid pathway for PAC biosynthesis and enhancing carotenoid sink capacity in green and non-green plant tissues,especially in lipid-storing seeds,and thus paves the way for further optimization of carotenoid biofortification in crops.