Improving dryland maize productivity and water efficiency with heterotrophic ammonia-oxidizing bacteria via nitrification and cytokinin activity

A two-year field experiment conducted under dryland conditions in semi-humid and drought-prone regions of China aimed to assess the effect of ammonia-oxidizing bacterial on maize water use efficiency and yield.A heterotrophic ammonia-oxidizing bacteria(HAOB)strain S2_8_1 was used.Six treatments were applied:(1)no irrigation+HAOB strain(DI),(2)no irrigation+blank culture medium(DM),(3)no irrigation control(DCK),(4)irrigation+HAOB(WI),(5)irrigation+blank culture medium(WM),and(6)irrigation control(WCK).Results revealed that HAOB treatment increased maize growth,yield,and water use efficiency over controls,regardless of whether the year was wet or dry.This improvement was attributed to the accelerated nitrification in the rhizosphere soil due to HAOB inoculation,which subsequently led to increased levels of leaf cytokinins.Overall,these findings suggest that HAOB inoculation holds promise as a strategy to boost water use efficiency and maize productivity in dryland agriculture.

Genomic evolution and insights into agronomic trait innovations of Sesamum species

Sesame is an ancient oilseed crop with high oil content and quality.However,the evolutionary history and genetic mechanisms of its valuable agronomic traits remain unclear.Here,we report chromosome-scale genomes of cultivated sesame(Sesamum indicum L.)and six wild Sesamum species,representing all three karyotypes within this genus.Karyotyping and genome-based phylogenic analysis revealed the evolutionary route of Sesamum species from n=13 to n=16 and revealed that allotetraploidization occurred in the wild species Sesamum radiatum.Early divergence of the Sesamum genus(48.5–19.7 million years ago)during the Tertiary period and its ancient phylogenic position within eudicots were observed.Pan-genome analysis revealed 9164 core gene families in the 7Sesamumspecies.These families are significantly enriched in variousmetabolic pathways,including fatty acid(FA)metabolism and FA biosynthesis.Structural variations in SiPT1 and SiDT1 within the phosphatidyl ethanolamine-binding protein gene family lead to the genomic evolution of plant-architecture and inflorescence-development phenotypes in Sesamum.A genome-wide association study(GWAS)of an interspecific population and genome comparisons revealed a long terminal repeat insertion and a sequence deletion inDIR genes of wildSesamum angustifoliumand cultivated sesame,respectively;both variations independently cause high susceptibility toFusariumwilt disease.A GWAS of 560 sesame accessions combined with an overexpression study confirmed that the NAC1andPPOgenes play an important role in upregulating oil content of sesame.Our study provides high-quality genomic resources for cultivated and wild Sesamum species and insights that can improve molecular breeding strategies for sesame and other oilseed crops.

The Hardy Rubber Tree Genome Provides Insights into the Evolution of Polyisoprene Biosynthesis

Eucommia ulmoides, also called hardy rubber tree, is an economically important tree; however, the lack of its genome sequence restricts the fundamental biological research and applied studies of this plant species. Here, we present a high-quality assembly of its ~l.2-Gb genome （scaffold N50 = 1.88 Mb） with at least 26 723 predicted genes for E. ulmoides, the first sequenced genome of the order Garryales, which was obtained using an integrated strategy combining Illumina sequencing, PacBio sequencing, and BioNano mapping. As a sister taxon to lamiids and campanulids, E. ulmoides underwent an ancient genome triplication shared by core eudicots but no further whole-genome duplication in the last ~125 million years. E. ulmoides exhibits high expression levels and/or gene number expansion for multiple genes involved in stress responses and the biosynthesis of secondary metabolites, which may account for its considerable environmental adaptability. In contrast to the rubber tree （Hevea brasiliensis）, which produces cis-polyisoprene, E. ulmoides has evolved to synthe- size long-chain trans-polyisoprene via farnesyl diphosphate synthases （FPSs）. Moreover, FPS and rub- ber elongation factor/small rubber particle protein gene families were expanded independently from the H. brasiliensis lineage. These results provide new insights into the biology of E. ulmoides and the origin of polyisoprene biosynthesis.