Identification of Fusarium wilt resistance gene SiRLK1 in Sesamum indicum L.

Sesame Fusarium wilt(SFW),caused by Fusarium oxysporum f.sp.sesami(Fos),is one of the most devastating diseases affecting sesame cultivation.Deciphering the genetic control of SFW resistance is pivotal for effective disease management in sesame.An inheritance study on a cross between the highly resistant variety Yuzhi 11 and the highly susceptible accession Sp1 using a Fos pathogenicity group 1 isolate indicated that resistance was conferred by a single dominant allele.The target locus was located in a 1.24 Mb interval on chromosome 3 using a combination of cross-population association mapping and bulked segregant analysis.Fine genetic mapping further narrowed the interval between 21,350 and 21,401 kb.The locus Sindi_0812400 was identified as the SFW resistance gene and officially designated SiRLK1.This gene encodes a specific malectin/receptor-like protein kinase with three putative tandem kinase domains and is considered a kinase fusion protein.Sequence analysis revealed that a high proportion(49.44%)of variants within the locus was located within the kinase domainⅢ,and several of which were evidently associated with the diversity in SFW response,indicating the critical role of kinase domainⅢin expression of disease resistance.These findings provide valuable information for further functional analysis of SFW resistance genes and marker-assisted resistance breeding in sesame.

Deletion of a 1,049 bp sequence from the 5′UTR upstream of the SiHEC3 gene induces a seed non-shattering mutation in sesame

Sesame is a labor intensive crop with limited mechanized harvesting mainly due to the seed shattering(SS)trait.In this study,we performed a genetic analysis of the seed-shattering resistance(SR)trait with a SR sesame mutant 12M07.Unlike the SS type,the parenchyma cells in the abscission zone of the 12M07 mutant are arranged loosely but adhere to the seed coat.Inheritance analysis of six generations derived from 12M07(SR)×Xiangcheng Dazibai(SS)showed that the SR trait is recessive and controlled by a single gene pair.Association mapping of the F2population with 888,619 variants(single-nucleotide polymorphisms(SNPs)and insertion-deletion(InDels))and 31,884 structural variations(SVs)determined that only SV12002 in the 5′upstream region of gene Sindi0765000(named SiHEC3)in Chr.3 was significantly associated with the SR trait.SiHEC3 encodes the bHLH transcription factor.A 1,049 bp deletion occurred in the 5′UTR of Sihec3 in 12M07.SiHEC3 is mainly expressed in developing placental tissues,with the expression peaking in capsules at 45 days after pollination.A dual-luciferase reporter assay in tobacco confirmed that the promoter activity of Sihec3 was reduced because of the deletion of the 1,049 bp promoter sequence.Protein–protein interaction network analysis showed that HEC3 is co-expressed with nine key proteins,such as SHATTERPROOF1(SHP1)and SEEDSTICK(STK)which participate in the secondary wall biosynthesis of the abscission layer in plants.The findings of this study show the important function of Sihec3corresponding with the SR trait and supply the genetic information for breeding new varieties that are amenable to mechanized harvesting in sesame and other crops.

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.

LOWER TEMPERATURE 1 Enhances ABA Responses and Plant Drought Tolerance by Modulating the Stability and Localization of C2-Domain ABA-Related Proteins in Arabidopsis

Plasma membrane-associated abscisic acid(ABA)signal transduction is an integral part of ABA signaling.The C2-domain ABA-related(CAR)proteins play important roles in the recruitment of ABA receptors to the plasma membrane to facilitate ABA signaling.However,how CAR proteins are regulated remains unclear.In this study,we conducted a genetic screen for mutants with altered leaf transpiration and identified an uncharacterized protein,LOWER TEMPERATURE 1(LOT1),which regulates the dynamic localization and stability of CAR proteins.The lotimutant had a lower leaf temperature as compared with the wild type due to higher transpiration.We found that LOT1 physically interacts with CAR9,and ABA reduces LOT1-CAR9 interaction in the nucleus,likely via Ca^2+,resulting in increased localization of CAR9 to the plasma membrane.We further found that the stability of CAR9 is affected by LOT1 less CAR9 proteins were accumulated and more were ubiquitinated in lot1.While the lot1 car9 and/of f car9 mutants were hyposerisitive to ABA,the hyposensitive phenotype of loticould be rescued by CAR9 overexpression.Collectively,our study reveals that LOT1 regulates plant tolerance to drought stress by affecting ABA signaling through regulating the stability and dynamic localization of CAR9.

An MCIA-like complex is required for mitochondrial complex Ⅰ assembly and seed development in maize

During adaptive radiation,mitochondria have co-evolved with their hosts,leading to gain or loss of subunits and assembly factors of respiratory complexes.Plant mitochondrial complex Ⅰ harbors40 nuclearand 9 mitochondrial-encoded subunits,and is formed by stepwise assembly during which different intermediates are integrated via various assembly factors.In mammals,the mitochondrial complex Ⅰ intermediate assembly(MCIA)complex is required for building the membrane arm module.However,plants have lost almost all of the MCIA complex components,giving rise to the hypothesis that plants follow an ancestral pathway to assemble the membrane arm subunits.Here,we characterize a maize crumpled seed mutant,crk1,and reveal by map-based cloning that CRK1 encodes an ortholog of human complex Ⅰ assembly factor 1,zNDUFAF1,the only evolutionarily conserved MCIA subunit in plants.zNDUFAF1 is localized in the mitochondria and accumulates in two intermediate complexes that contain complex Ⅰ membrane arm subunits.Disruption of zNDUFAF1 results in severe defects in complex Ⅰ assembly and activity,a cellular bioenergetic shift to aerobic glycolysis,and mitochondrial vacuolation.Moreover,we found that zNDUFAF1,the putative mitochondrial import inner membrane translocase ZmTIM17-1,and the isovaleryl-coenzyme A dehydrogenase ZmIVD1 interact each other,and could be co-precipitated from the mitochondria and co-migrate in the same assembly intermediates.Knockout of either ZmTIM17-1 or ZmIVD1 could lead to the significantly reduced complex Ⅰ stability and activity as well as defective seeds.These results suggest that zNDUFAF1,ZmTIM17-1 and ZmIVD1 probably form an MCIA-like complex that is essential for the biogenesis of mitochondrial complex Ⅰ and seed development in maize.Our findings also imply that plants and mammals recruit MCIA subunits independently for mitochondrial complex Ⅰ assembly,highlighting the importance of parallel evolution in mitochondria adaptation to their hosts.