Comparative population genomics dissects the genetic basis of seven domestication traits in jujube

Jujube(Ziziphus jujuba Mill.)is an important perennial fruit tree with a range of interesting horticultural traits.It was domesticated from wild jujube(Ziziphus acidojujuba),but the genomic variation dynamics and genetic changes underlying its horticultural traits during domestication are poorly understood.Here,we report a comprehensive genome variation map based on the resequencing of 350 accessions,including wild,semi-wild and cultivated jujube plants,at a>15×depth.Using the combination of a genome-wide association study(GWAS)and selective sweep analysis,we identified several candidate genes potentially involved in regulating seven domestication traits in jujube.For fruit shape and kernel shape,we integrated the GWAS approach with transcriptome profiling data,expression analysis and the transgenic validation of a candidate gene to identify a causal gene,ZjFS3,which encodes an ethyleneresponsive transcription factor.Similarly,we identified a candidate gene for bearing-shoot length and the number of leaves per bearing shoot and two candidate genes for the seed-setting rate using GWAS.In the selective sweep analysis,we also discovered several putative genes for the presence of prickles on bearing shoots and the postharvest shelf life of fleshy fruits.This study outlines the genetic basis of jujube domestication and evolution and provides a rich genomic resource for mining other horticulturally important genes in jujube.

The mitochondria-localized protein OsNDB2 negatively regulates grain size and weight in rice

Grain size is a determinant of rice grain yield.In plants,mitochondria supply energy for cellular metabolism via the mitochondrial electron transport chain.Here we report that OsNDB2,which encodes a putative rotenone-insensitive typeⅡNAD(P)H dehydrogenase(ND),negatively regulates grain size and weight in rice.Six ND members representing three major types of rice were identified,and the predicted OsNDB2 protein was localized to mitochondria.Contents of OsNDB2 transcripts were higher in young panicles and leaf blades.OsNDB2 overexpression reduced grain length,grain width,and 1000-grain weight and moderately influenced plant height,while knockout of OsNDB2 increased grain size and 1000-grain weight.Allelic mutations of OsNDB2 were associated with diverse grain appearances.Cellular observations revealed that variations in grain size of transgenic lines were caused by change in cell expansion but not cell proliferation in spikelet hulls.Our study sheds light on OsNDB2 function and provides a new potential breeding approach for increasing rice grain size and weight.

Synthesis and characterization of an amphiphilic chitosan bearing octyl and methoxy polyethylene

An amphiphilic N-octyl-O-methoxy poly (ethylene glycol) chitosan was successfully prepared by grafting successively octyl groups onto amino groups at chitosan’s C-2 position as hydrophobic moieties and methoxy polyethylene glycol (MPEG) groups onto hydroxyl groups at C-6, C-3 as hy-drophilic ones. A certain amount of -NH2 was retained in the structure of chitosan derivatives through protection by phthalic anhydride. The chemical structures and degree of N-and O-substitution of chitosan derivatives were characterized by FTIR, 1H NMR, GPC and elemental analysis, respectively. The amphiphilic property for convenient self-assembly and the preserved -NH2 groups for progressive chemical cross-linking make the resultant Nocyl-O-MPEG chitosan soluble in water and potentially applicable in preparing stable chitosan hollow microspheres, a demanding drug-carrier in medical and pharmaceutical sciences.